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#1071669 - 08/18/21 06:22 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Well the test drive on Sat bombed. A 3 mile trip around the block with some 55 mph and the temp gauge was going nuts. Idling was good, about 180 degrees, out on the highway the temp gauge was 190, then quickly 225, then back down then up again, not boiling hot just never had a ranging problem like this before.
Had the pyrometer with me on the second quick trip to shoot block and heads and was seeing 225. As soon as the car was stopped i jumped out and checked temps while running.

Back in the shop now looking for anything other than what I think the problem is. A timing light showed to much initial advance, 22 degrees. 17 is what is set. A lot of advance is run in this engine. 17 initial, 37 total with a 19 degree vac advance. It's a lot of timing at 2300, about 52-54, but what the engine likes and needs for economy at 70 mph. If the initial is 5 over that puts cruise timing in the high 50's. Usually lots of timing on light load tend to cool the engine. Can't see how all the timing relating to running erratically hotter.
Looking for a reason for the+5 degrees initial pulled the cap and rotor to look at the centrifugal in the Pertronics HEI. Several years ago had a problem there. One of the pins broke the weld and was laying over, had it TIGed and fixed that problem. So was looking for another possible problem with the centrifugal. Weights, springs, pins, everything is good. But look under the rotor and notice the weights are rubbing the rotor. HUH. Pulled a couple old rotors laying around and saw no where a touching of any kind. Did some measuring and found the rotor's mounting surface was a little bit different from those old quality rotors. The condition and quality of the cap and rotor are very good, phasing is great, reuse them. To clearance the weights a fiber shim of .037" was cut to fit the mounting tabs and this lifted the rotor up for weight clearance. Time will tell how that works out. Next put the timing light back on and see if the timing was effected by the weights contacting the rotor and not allowing them to return to zero centrifugal advance.
If not will reset initial to 17 and go from there. It's unusual for the timing to advance, as things wear timing retards. Did the dist move, advance, I doubt it.

With 4 different thermostats, old Stant 180, two new Motorad 180 and a Delco 180 they all went to the kitchen stove to get cooked. The old Stant started to open over 190 and slowly until full open at 205. The Motorad where a little over 180 and full open at 192, the Delco 183 and full open at 195. I chose to put the USA Delco back in the engine. I would say the old Stant that was in the engine for a decade was out of spec.
Had drilled a 1/8" hole in the Delco before install for the last test trips in the car. The previous Stant had three 3 /16' holes in it. I attribute some of my last overheating to only an 1/8" hole. A Dart block doesn't have the 3/8" coolant recirc hole at the left side of the pump mount. On a normal SBC when the thermostat is closed the pump pushes coolant into the block, that 3/8" recirc port feed coolant back into the suction side of the pump. A Dart bock with the thermostat closed has no recirc until the thermostat starts to open. By drilling three 3/16" holes in the thermostat plus the 1/4" tube dumping coolant to the thermostat housing that equals closely the flow of that 3/8" recirc hole in a SBC. The down side to that is engine warm up takes much longer due to the water to the pump is now is coming from the radiator, cold. It's just something i need to live with.
So the Delco thermostat now has three 3/16" holes and is in the engine.

Now the real PITA. What it boiled down to is an entrained Stewart water pump. When this engine was being fired up for the first time a Stewart water pump was installed. I fought with coolant non-circ for a month trying to figure out why the pump wouldn't just pump and get water moving like every other SBC I filled up with coolant and drove away. Numerous calls to Stewart tech, tried raising the front of the car 2 foot higher, back of the car, nothing, just wouldn't circulate. After weeks I finally bought an Edelbrock pump and the first try water is circulating. Sent that Steward pump right back to the Stewart tech for checking. They sent me a new pump but said nothing was wrong with the old one. Well a couple year later running 110+ though the traps the powdered metal Edel pump impeller blows up, pushed the plate off the back of the pump, left my car sitting in the pits until the next day when I could trailer it home. Not happy.

Now with a Stewart that doesn't pump, and Edel that blowd up ordered a Weiand Team G. Stamped in the rear cover in huge letters CHINA. Back in the box and returned. A stock cast iron out of the question. So pulled the new Stewart that they sent me and I need to make this work. Well it was a lot of aggravation, but an elaborate mix of hoses and pressure forcing coolant through the pump and it pumped. What happens is air gets trapped in the top of that pump and no way to get it out. Forcing coolant at pressure was able to dislodge that air. Pulling the rear covers on the Stewart, Edel and an old junk cast iron pump you can see how it can get trapped in the larger open space of the Stewart. I'm pretty sure air entrainment is the problem and added to that the Dart block has no recirc to the pump that may help move that dead air.

Air in a pump greatly reduces it efficiency,, and as rpm increase efficiency is reduced even more. I believe the reason for the coolant temp to sharply rise and fall at different rpms.
And also knowing even after two heat and complete cool down cycles there was still 6 oz sitting on the bench that needed to go back into the system from the draining. Almost positive it should be in the pump

Knowing a little about vacuum filling a cooling system i decided that was the next step to get this car back on the road. After looking at numerous vac fill tools, videos, was set on being this one. Don't need 25 adapter for different rads so a simple kit that fits most of what I work on will do. And it's made in Canada, go figure.
https://www.matcotools.com/productassets/web-documents/AC550000_PartsBreakdown_01.pdf
Before buying one and waiting three days or more for delivery I stopped to see a mechanic friend this afternoon. He said the one he has he got from Matco about a year old and was never used. He pulls it out of his cabinet and it's exactly the one i was going to buy, and, take it with you and see how it works.
Had a little time to play with it today and sucked in a coolant charge but stupid me forgot to open the heater valve. Ran out of time but will be at that again tomorrow. It's really slick the way if pulls the coolant into system. There just a few particulars to pay attention to but once you have the knack it's stupid simple.
I'll eventually buy a 540000 for the future.
I'll know in short order if it works as expected because all the coolant removed will put the overflow tank right back at the cold fill mark if everything goes well.
Hoping for a test drive tomorrow with no temp gauge dancing.
Bob

#1071674 - 08/18/21 03:07 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Very interested in this as I have a neighbor with a SBC in a Chevy II that has been fighting an overheating issue all summer and we can't seem to find the cause. I keep coming back to his water pump as well, almost HAS to be that. He has a Eddie Motorsports front runner kit on it and I was convinced it had the wrong rotation pump installed...but an air pocket in the pump would also explain his strange over heating issues for sure.

His seems to be fine under most circumstances but once a load is put on the engine, it starts to heat up and never cools back down again. It'll idle in driveway in 105* temps with the AC on high for an hour and be okay, 7 minute drive down the road under load and temps start climbing and never recover...


Lance
1985 Monte Carlo SS Street Car
#1071675 - 08/18/21 04:54 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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I'm guessing you have checked the thermostat? Is it possible that it is slowly opening, sticking in place, and not opening the rest of the way? Just a thought. It's a head scratcher on both for sure, the air bubble in the water pump seems to make sense.


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1071708 - 08/20/21 06:31 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Lance you didn't mention what pump, block, fans, radiator are in the car. Assuming the Eddie is a serpentine setup.

Well after sucking a vacuum and filling of the cooling system 4 times with the AirLift 520000 i figured just how to do the correct procedure to get the pump and rest of the engine 99% full. With this engine/cooling system it's a little tricky. First two times it was just for the fun of it and made mistakes. Third time I was thinking a little bit more of the drained coolant should have been sucked in. 4th time I plugged the Mighty Vac into the hose coming from the Vac ball reservoir and applied 15" to the vac system to the heat/A/C control to insure the heater flow valve remained full open while filling.

Because the rad cap is on the side of the rad you can't get the top of the rad full, an air pocket will still be there after refill. That air is removed as the coolant cycles through several hot-cold cycles. Eventually the coolant overflow will put the rest of the coolant in and remove the pocket of air in the top of the rad.

Weds night after the 4th refill started the engine and let it idle until running temp, 180. Several years ago installed a bleeder Tee close to the exit of the heater core. The logic was that is the highest point in the cooling system. After extended idling with the heater on, opened that bleeder and still had air trapped in the hose. A steady stream of coolant should come out of that bleeder when the system is under pressure, nope. Hmmm. Turned off the lights and went home.

This afternoon checked the coolant level in the reservoir, it had gone down about 1/4", good, top of rad is near filled. Out for a 3 mile trip around the block watching the temp gauge. Cool, it's now steady, no ranging between 190 and 225, steady at assumed 185 via a pyro on the temp sender. Idling back in the shop and it now a steady stream of coolant out the heater hose bleeder, good. Let it cool down and checked tonight, 1/4" below the full line in the reservoir. GOOD. I figure once all this hot-cold thing finishes the 100% full system it's done. I will need to add maybe 6 oz for the coolant i lost due to all this draining and filling of the system. Stuff left in hoses, buckets, filtering, splash when draining, results of 4 vac fills.
BUT I DO THINK THE SYSTEM IS FINALLY FULL, no air in the pump..

Tomorrow will drive again to get engine hot before going back to tweaking the A/C system charge. Thinking I may be back to normal with the cooling system and electric fans doing what they should.
Today was another 92 degree day, was seeing 190 ish at the temp sender, 178 at the inlet to the rad and 135 at the fan sensor in the lower rad hose. Those rad temps are what I saw before all these problems started months ago. That's a 35 degree drop across the rad, dual 11" Spal fans are doing their job.

Today I called Dart tech to get an answer about why no coolant bypass in their blocks. The answer i got was the block was designed 20 years ago and that engineer is gone now. OK. But we both think it's because of the amount of cast iron around and to the front of #2 cylinder for strength, the .200" think cyl walls and the fact the block can be bored to 4.185 without problems.

For now done with the recirc thing and know the four holes (three 3/16"in the thermostat, 1/4" tube from the intake at #7 and #8) provide close to equal volume for recirc. But slow warm up is the end product. If another water pump would go on I would plumb a 3/8" line from the heater core supply hose and dump it in the inlet of the pump to create a better recirc loop. Not really difficult to do. Hindsight. Could then not have to have all those holes in the thermostat.

Cleaned up that brand new Air Lift tool and returned it along with a 1/2 dozen tomatoes and some jalapeno and habanero I picked fresh from my garden. He said BLTs where on the menu for dinner now.
Next week will order one of those AitrLifts for my tool box. Great, high quality tool, make refill easy once you have the technique down.

When I charged the A/C system 14 years ago I looked for a Tee for the high pressure port so my gauge and the high pressure switch i use to control the fans could be used on the port at the same time. No luck. Last week ran across a Tee and it's now sitting on the bench ready to use tomorrow. It will make watching how the high pressure switch and the electric fans interact while watching the gauge, real time monitoring now. As mentioned the high pressure switch turns the fans on and off, not clutch activation.

Next Fri the car makes the trip to the KOTM event, a 550 miles round trip, a good test drive to see if the cooling and A/C systems are working properly. Cutting it close but thinking we're good to go.
Car prep for the trip is just a matter of install the the old 16" wheels and tires and saving the new 17" wheels and RT660 tires for two autox event i hope to be able to make this year yet. Also don't have a lot of confidence in driving that 660 tread pattern (or lack of it) in the rain at 70 mph which is most of the 550 miles. Last years trip to KOTM was the first two hours in pouring rain.
Bob

#1071715 - 08/20/21 04:15 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Glad to hear you have everything straightened out. Im willing to bet your temp will stay at a nice even 180° and the ac will be blowing cold for your trip to KOTM.

Last edited by 88ssBrent; 08/20/21 04:15 PM.
#1071716 - 08/20/21 04:24 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Good work Bob! Can't wait to see you next week!

My neighbors car has an aftermarket aluminum radiator that we think is the culprit. It's a downflow type and the drivers bottom portion of the radiator is 40-50 degrees cooler than the whole rest of the radiator. The outlet portion of the radiator is the same temp as the inlet, basically the water is just flowing around the outside edge of the radiator instead of through the whole thing.

We've verified the water pump is pumping the correct direction and actually will suck the lower hose in when a restrictor is put between the lower hose and the radiator...the pump is working as it should.


Lance
1985 Monte Carlo SS Street Car
#1071724 - 08/21/21 05:59 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Back in the early 70's the toy was a 62 Nova with basically a 69 Z28 drivetrain, roller cammed of course. The radiator and fan shroud was the 4 core copper brass from the 69 Z, with the technology of the day a Flex-a-lite fan and the proper spacer. More than enough for that little mouse, that roared. That Harrison Z rad was a crossflow.

I thought downflow rads are for vintage stuff that doesn't fit crossflow well. My brother-in-laws 39 Plymouth, old 357 hemi and a big blower has a down flow because that's all the fits. He's has had his share of fun trying to keep that engine cool.

Assume electric fan, fans, proper coolant ratio, is this an A/C car,? Shiny alum parts are hard to get an accurate pyro reading from.

It took two flex fan failures to make me never use one again. First was in the Nova at the drag strip, a blade came off and struck the sending unit for my Super Sun tach killing it. Luckily the S&W parts trailer was in the pits and had a sender. back off to the races. Costly day but didn't pay that bill until a few days later at the speed shop. Second failure was in my 69 C10 with a fresh 350 mildly build, stick shift. A quarter of the way out on a 2000 miles round trip vacation, think I was looking at Ohare on my left, a blade flew off the Flex-a-lite on that engine. Found a speed shop in Minneapolis, only available thing was another Flex-a-lite, my very last!.

Enough about the fun days.

It rained today, very short trip round the block between rain drops to get engine hot. Temp gauge showing about 180-185 steady, no wandering all over the place anymore. A long extended idle period while playing with the A/C and very happy the cooling issues are done. Tomorrow morning ends another cool down cycle, should be all done with that and will measure in a quantity of new coolant to bring it to the line on the tank. Should be about 6 oz to replace lost coolant while doing this fiasco.
Using the pyrometer on header primaries, heads, block, even directly on the gauge sender when the engine is very hot can give you good info. Wish I had a pyro 30 years ago.

Forgot to mention, after seeing 5 degrees more initial timing at 600 rpm and finding possible interference between the centrifugal advance weights and the underside of the rotor, shimming the rotor up .037", the timing was back at 17 degrees on start up. Maybe my fault. The ignition is a conglomerate of parts. A Pertronic dist with a Comp Composite gear, advance weights are GM HEI, cap/rotor/coil are DUI, vac advance a speced unit, no module just a pickup feeding a processor in the console which takes care of dwell, rev limiter and knock retard.
So fixing that +5 advance problem required attention. But it was several years since last looking, checking those parts. But all is well now. Even checked the idle fuel pressure, idle vac, timing, advance rates, idle A/F, carb screws and bolts, vac lines, hose clamps, all those PM things you need to address periodically.
Never would have thought weights hitting the rotor was a cause if i didn't clean the bottom of the rotor, and having my reader glasses on.

First round of A/C checks didn't go well. It works good for a 90+ day but need to get vent temps back below 40 degrees. One thing I did learn is when the hood is up, it leaves a clear path for hot air to enter into the fresh air intake, pass side of the cowl, for the heated air to influence evap performance, dash vent temp. With gauges connected it hard to close the hood as recommended in doing performance checks. Sitting in the shop idling and driving down the highway

Checking Super Heat requires reading freon line temp at the inlet of the evap. I use electrical tape, bury the tip of my Flute temp probe against the tubing and get an accurate reading for Super Heat. Then transfer the probe to tubing just ahead of the orifice, tape it down and get a Sub Cool temp. Problem is frost on the evap inlet tube doesn't allow re-taping the probe, no stick.
Need another Fluke probes so the one on the evap inlet can be left in place. Have a digital bulb thermometer but difficult to get a good stick on the vapor line.
So still working on getting accurate number on whats going on and how Super Heat and Sub Cool tuning impact system performance. The specs for the stock system in the Helm's Service manual are not operating system perf specs, but just ranges for a tech to say "good to go", "can't see it from my house".
Finding credible info on an old GM R12 system is all but non existent. If some of you remember, "A/C isn't as good as it was last year, stop at the Boys and pick up a can of 12. Add until you see the accumulator sweat." There's so much more to it.

That Tee to use on the high pressure port i bought doesn't fit. The high pressure port is 3/16" thread, not 1/4". the high pressure switch is 3/16". I use an adapter hose from 3/16" female to 1/4" male to attach my high pressure gauge hose, 1/4" female. Sorry about misinformation. The adapter hose is Four seasons #59600 which I see is all but extinct.
Bob

#1071743 - 08/22/21 05:41 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Had a little time today to spend with the car. Put the gauges and temp probes on the A/C to see if i could dial in a Super Heat and Sub Cool and get this thing done.

First checked the coolant reservoir when cold, it was lower than yesterday. More coolant is now back in the system and should be close to no air anywhere. The top of the rad is one of those places where a little air can be trapped until several heat-cool cycles removes it. Now was a good time to top off the reservoir to the full line, 8 oz was added. That's about what i thought should be added to make up for lost coolant during all the draining and refill done. Will check again but think good to go now, no entrained air in the system.

Again 92 in the shop and engine idled for a long time while watching the A/C running at max and engine temp I was happy with. Rain, hurricane coming through on Sun, no cars and coffee for a test drive tomorrow morning.

A quick version of the Super Heat number is liquid temp into the evap verses vapor temp out. Temp out is a fixed number derived from freon type used and the low pressure gauge number. Temp in is the temperature of the freon liquid going into the evap. The difference between those temps is Super Heat.
.
Sub Cool number is how much high pressure vapor is turned into liquid in the condenser. The temp into the condenser is derived from the freon type and high pressure gauge number relation. Temp out of condenser is a measured at the outlet of the condenser tubing. The difference between them is Sub Cool.

So with gauges on the A/C and a temp probe on the evap inlet time to play with Super Heat. I know from the other day Super Heat degrees was way to low, and frosted the alum tube at the compressor. That is a big NoNo , can't have any liquid going to the compressor, shortens it life quickly. That's when i went home on Fri, rethink the process.
Today removed some of the freon first thing, overcharged, and got the Super Heat temp up to the 10 degree neighborhood. Being there is no spec for what that number should be it's a guess and trial and error watching how the evap reacts to changing Super Heat caused by low pressure change and watching the vent temp as an indicator of evap performance. I think the trick is paying attention to the Super Heat as the system low pressure varies. It will range from 10-12 degrees Super Heat as the low pressure changes when the compressor is cycling on and off. Being the car is sitting inside, 90+ degrees, hood up and a lot of heat around the engine getting a real world numbers of driving the car is not possible. Yes very long hoses and tempo sensor leads and you could bring them inside the car to view while driving, but.

A check of the Sub Cool and I was in the 10 degree area, and it will also vary as the high pressure changes during cycling. So close to a 10-10 balance right now, the proof will be out on the highway to see if the vent temps are acceptable. Had 42 at the vents with some 100 degree outside air being sucked across the evap coil while cooking in the shop.
Have read, and viewed numerous school "classes" on line about balancing an A/C system and optimizing performance. But there is a delicate balance and automobile A/C may be the most difficult because it's literally a moving target. Residential A/C is easier, it doesn't move and they tell you the specs for Super or Sub at a given ambient making it easier to dial in a correct charge.
Bob

#1071751 - 08/22/21 06:43 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Just ordered one of these for the next time the coolant filling frustration happens. Price is very good from these people. The Matco man is 200 bucks with taxes.
https://www.jbtools.com/uview-550000-airlift-cooling-system-tester/
Don't usually recommend tools but quality and function were excellent.

Looked at several other vac bleeders sold for much cheaper but plastic and of course over seas quality. Harbor Freight is 1/4 mile from me, that was my last resort before borrowing the 550000 I used the other day. Luckily a friend mechanic saved the day by lending his 550000, and I didn't spend 80 bucks at Harbor.
Eastwood is a 1/2 mile the other direction, sell this, no need for all those adapter and pay that price.
https://www.eastwood.com/astro-pneu...acuum-type-cooling-system-kit-78585.html

With all the times having problems with filling this engine and the many times I've filled other engines this tool will pay for itself.
Bob

#1071755 - 08/23/21 12:39 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Bob, I have to say that your thread has made me read and watch more ac videos than I ever thought I would. It really makes me want to dig in on mine but as I said in my build thread that is going to have to wait till next spring. Im just glad you are getting everything squared away. I know you pride yourself on downtime and this go around has been a doozy.

#1071762 - 08/23/21 05:53 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Part of all this is that I'm not cheap, just don't like others doing what I can do myself. In the near future going to install a split A/C system in the house and need to have a better grasp of what's involved. I hear some install prices and know material is 1/3 the cost, and seeing rain downspout hanging on the side of the house doesn't say quality. So even though I've been around commercial A/C for decades and working with techs you just never do get the big picture, knowing why it works requires a little education. Had done three different car A/C system R&R prior to this last one, and just did them by the book not knowing the why, just the how. All were successes. But this last one became a little more complicated because A/C failure was caused by a Sub Cool problem, the fans and controller issue.

Downtime is a big deal for me especially in the prime time of the car season. Every year I try to drive it 2000 miles minimum to have a reason to own the 86. Last year even in pandemic mode managed 1875. Next weekend will put near 600 on the odometer going to KOTM. That will be a good road test for the recent cooling, A/C problems.

Yep lots of good video on A/C, lots of not so good also. But hard to find anything specific about old car A/C, except the 12 to 134 conversions. Lot of "how", but really no "why" of how to tune an old car system. Even less on a old fixed orifice 12 system. So for me it's a live and learn, trial and error approach to put a tune on it so I can live with for the next, well, hopefully decade. I hate doing thing twice.
Bob

Last edited by mmc427ss; 08/23/21 05:56 AM.
#1071768 - 08/23/21 03:21 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Couple of thoughts on the AC... On your superheat, are you measuring Evaporator superheat or Suction superheat? i.e., are you measuring the temps on the line pre-accumulator or post? If you have 10° pre-accumulator, that's probably low charge and you will have tons of superheat at the compressor, where it actually matters. Another term for the accumulator is a "Superheater", as that is it's main job on an auto AC system.
The her thing is using the blower on "Max" setting with windows down and possibly passenger door slightly open to get a steadier evap inlet temp without picking up all of the hot air from the cowl. You can also make a shield from cardboard and/or foam pool noodles to get the flow a little less hot.


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1071788 - 08/24/21 02:22 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Thanks Shawn.
It hard to say how much hood up, 95 degrees in the shop, and all that engine heat influences the fresh air intake in the cowl. Supposedly when in MAX it's recirced cabin air, no make up. But would think some of that super heated dry air is being sucked down the cowl intake.
Just for fun I'll see if a piece of paper gets sucked to the inlet.

Measuring with a bulb right at the inlet of the evap, multiply layer of electrical tape to hold and insulate it.. Feel that's getting accurate temp. Using the PT numbers from my fresh set of gauges, zeroed, on the low pressure port on the accumulator.
When I first started to play with charge at first it was the hand method, warmer evap outlet than the outlet. Next it was the pyro but shooting silver, alum, isn't reliable. Tried black tape and wasn't going to rely on the numbers. Painting a small area flat black would probably be ok.
For Sub, bulb temp sensor taped to alum tubing just before the high pressure port, using PT numbers from my high pressure gauges.
Decided do my best with the PT numbers taken at the low pressure port and the bulb on the inlet. Because there are so many variable.

Or maybe should I buy a second bulb temp sensor and have one on the inlet, one on the outlet of the evap and ignore the PT charts?

Is it fair to say on these cars you shoot for Super heat that gets the most out of the system then back off a little to protect the compressor. The condenser side of the equation has so many variables to deal with as far as temp and airflow. Sitting at a red light or running down the highway at 70, 95 ambient or 75, engine compartment temp. Not to mention engine rpm and compressor rpm. Now make it an orifice tube system and just makes all that more interesting.

Most of what I've seen and read says orifice, deal with Super, TXV deal with Sub. An orifice system is harder to make right because of the fixed orifice, a TXV will adjust flow according to outlet evap temp. Didn't the old, 70s cars, use a form of TXV?

Still have the same questions. On this 12 system what would the range of Super be, and can you assume you want the Sub and the Super to be close to balanced, say 10-10. I understand condenser flooding and the same with the evap. With so many variables where is that happy medium.

Saw this digital pressure- temp gauge set demoed. Pretty cool, would think a stupid person could tweak a system with it.
https://www.trutechtools.com/Fieldpiece-SM480V
Bob

#1071791 - 08/24/21 04:43 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Man, that gauge/thermocouple/scale combo unit sure would make life simpler. One tool to do it all... But $600 is a little outside the range I can justify to avoid juggling gauges and probes etc. Maybe one day though. If you can get a clothes pin or even just a zip tie to hold the probe in contact with the tube, that should get you pretty good numbers. Bonus if you have a little square of foam insulation, put that over the top of the probe and hold that down on the tube with some kind of pressure. You get good contact, and the insulation keeps the reading from being as affected by the air around it.

It's generally safe to assume that you will have the same low side pressure pre-evap, post-evap, and post accumulator. Realistically there's going to be a psi or two lost, but not enough to worry about. The temperatures between those spots will all change quite a bit though, and that is exactly what you are looking for. The superheat measurement is going to be the difference between your saturation temperature that you read off the gauge for the pressure you are running and the measured actual temperature off of your suction line, either before or after your accumulator. If you are wanting to tune your orifice tube, you would probably want to measure between the evap outlet and the accumulator inlet to pick your orifice or tune the charge. But for a given system and making sure you are protecting your compressor, superheat at the accumulator outlet is what you need to focus on, as that is the only thing that matters to the compressor.

In other words, I would expect near zero superheat before the evap, because the liquid should not really be boiling there. If the evap is filled with liquid and you get a couple degrees superheat after the evap (basically zero), that will get the most bang for your buck out of the small evap, as the liquid pulls more heat than gas.
And after leaving the evap, the accumulator is going to soak up heat from the engine bay and boil the rest, and the piping is made such that it should only be pulling from the top where the vapor is, so if you don't have any superheat there, you are washing down the compressor.

And to repeat myself a different way (my wife loves it when I do this) but with numbers, If you have 0° after the evap and 10°+ SH at the accumulator, you know that you are maximizing cooling at the evap but aren't flooding the accumulator and you have a fair amount of headroom before you do for differing conditions.
If you have 10° after the evap and 40° after the accumulator, you can add more charge (or open up the orifice size) to flood the evap better.
If you have 0° after evap and 0° after accumulator, you are still returning liquid to the compressor and it will not be happy for very long like that.
All of these are based on having essentially 0° at the evaporator inlet. If you have 10° there, you are not getting near the capacity that you could.

That trick of making sure the outlet is warmer than the inlet is based on trying to measure the superheat change across the evaporator by hand, which works in a pinch to make sure you have a good column of liquid into and out of the orifice tube while avoiding overcharging. TXV's give better operating ranges as long as they have liquid feeding them, and the way they work is by maintaining a set superheat. Based on that, they will always shoot for say 6° superheat, so you have to make sure you have enough subcooling feeding it, otherwise you could be way off on performance and not know it just looking at superheat. Fixed orifice has to be charged so you don't wash down the compressor for any given size, so you charge based on superheat. If you don't like the rest of the system numbers, you change the size in the design stage. You SHOULD be able to get a size that works well with the superheat, supcool, and capacity all balanced, but only one of those will destroy a system so that's why you want to look at superheat the most.

And for reference, we always considered superheat and subcool as +/-2°, even in a lab condition. Sometimes you read the gauge a little off, sometimes your gauge location and your temp location is just far enough away to affect it, sometimes the refrigerant specs are a little different from book value, etc.


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1071792 - 08/24/21 04:56 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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I should add, that is all theoretical, and the actual superheat numbers to keep your compressor alive is the charge that keeps gas and only gas going to your compressor under all conditions. cold weather, hot weather, high engine speed, low speed, high blower, low blower, etc. I'm thinking you would want to verify some superheat on max setting, low blower speed, on a 75° day at higher engine speed, I THINK that would be a reasonable worst case situation, and having a degree or two there should be enough. At 95° and blower on high with fresh air at idle, you might see 30° superheat after the evaporator on a good system, I don't know. But for reasonable charging conditions, warm day with fan on max and high and engine revved to 1500-2000 rpm (how everyone says to charge an auto system) ought to be a good baseline for comparison.


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1071826 - 08/27/21 05:30 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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It's been a couple days since last update. Tomorrow morning 8 am the car is making the 250 mile trip to UMI KOTM event. Have been to the first one, the second one and now the third with the 86 making the trip. This one is a little special, will be meeting Lance in person for the first time. And to top that off Kevin, (Crusher) and Frank, (Frank OC), all Forum member here will also be there, and we are all in the host hotel, and Frank will have beer. Should be a special weekend.

Weds was another hot, 99 index, day. A good day for a 30 mile trip around the block to see how the cooling system and A/C system behave.
The cooling is now full with the help of the AirLift vac refiller. Coolant level in the reservoir has maintained the same level when stone cold.
The temp gauge reading was steady, no wondering, showing a little warmer than before all this started but with the pyro saw 190 at the inlet to the rad. And that was under the extreme conditions, 100 degrees and A/C running the entire time, underhood temps were cooking.

A brand new AirLift 540000 was delivered on Weds. Should never need to be frustrated on filling this engine with coolant again.
Also have a good idea on how to get recirced coolant back to the pump when the thermostat is closed. Dart blocks don't have recirced coolant feeding the water pump, no bypass hole in the block. The only time a Dart block gets recirc is when the heater valve is open. A SBC with a heater has hot coolant out of the intake to the heater, cooler returns from the heater feeds into the pump inlet. Connecting the 5/8" heater supply to the 3/4" heater return with a short piece of 3/8" hose will supply bypass coolant to the pump and close to equal what the 3/8" bypass hole in a SBC has. The only downside is maybe the heater will be a tad less efficient but i doubt it. Not a big deal to make two brass Tee's to do that install, certainly can't source them anywhere.
The other benefit to adding that bypass would be the three 3/16" holes in the thermostat to produce bypass flow won't be needed. Would only need an 1/8" hole to bleed air then. Without the holes engine warmup would be faster and the 180 degree thermostat will be more in charge of maintaining temps under 180 degrees by staying closed.
So maybe another mod for the cooling system, but not needed right now.

Well A/C, the short of it is I'm not satisfied. System works and is withing the ranges show in the shop manual but know it could, should be better. The extreme ambient temps the other day on the test trip was a good test. Running on MAX and blower on high the best i saw was 42 out of the vent. At cruising speeds average was 44-45. I expect to see 40 and a tad lower 38-39 under idea conditions. Will be using the A/C a lot this weekend an will also see a lot of 50-70 mph driving. The little A/C thermometer at the shop will be a job for my navigator, Bill, along the way testing the vent temp. Should be able to get some ambient temps that aren't in the mid 90s in central Pa, I HOPE!
Typically if it 's going to be in the 90s the black 86 usually sits, no need to punish it in the sun if not necessary, and punish me for driving it. When the need arises, like this weekend trip, the A/C need to be available to keep me happy. And all touring cars have good A/C.

Will get back to looking at Superheat again next week. Ordered another temp probe for my Flute so will now be able to read inlet and outlet evap temp.

Order a new Metri-Pack 480 plug and extras female terminals for it. That is the GM connector I used on both the Spal electric fans. The pass side fan had an issue at that connector which i fixed, but need to have a standby waiting in the wings if needed.

Early up, early out the door tomorrow, happy trails.
Bob



Last edited by mmc427ss; 08/27/21 05:31 AM.
#1071827 - 08/27/21 01:51 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Enjoy the trip, and stay cool!


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1071848 - 08/29/21 06:43 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Well, how's was the trip and how did the cooling and ac do?

#1071864 - 08/30/21 05:02 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Got back early afternoon Sun from KOTM, just shy of a 600 mile round trip. The cooling system is back to where it was prior to all this carrying on, gauge temp is rock steady no mater 90 degrees, 70+ mph or idling hot. Last night, 12:30 am, actually needed the heater and defrost in UMI's back country parking lot. Hindsight now says I should have popped the hood to watch the compressor cycling in the cold defrost mode (heat and A/C) while it cleared the windshield. But it's not cool to be working on your car in the parking lot full of race car haulers and predominantly Chevy guys.

The coolant level cold has been spot on the line the last couple times checked. How much hot coolant that has been pushed over to the reservoir can be used as a visual measure of engine temp. Generally hot day, hot engine may see 1/4" above the line. When at that last autox and the engine overheated into the 230 range checking level was at 1" above the line, that's when i pulled the plug on the last two runs of that day.

Watching coolant level when cold I've monitored for years on this engine. You see that level change you look for, and fix that leak. A couple years ago suspected pissing out the back corners of the cyl head area, barely noticeable because it only happen under heavy accel periods, and left white dots on the stainless exhaust pipes. Assumed it was head gasket but could't follow a trail back to that source. Coolant level loss you could measure but was so minimal, hardly noticeable if you didn't pay attention to the level but white dots on the exhaust where present. Prior to that changed antifreeze to a Zerex GO-5, old antifreeze aged out. That GO5 antifreeze was the cause of my leaks at the head gaskets. Even with a couple of Bar's leak tablets i chased the source for months. Finally dumped the GO5 and flushed the system and installed Peak Global Lifetime with a tablet, no more white dots on the stainless exhaust. Monitoring coolant level for me is a good troubleshooting tool.

A side from maybe tweaking the temp sensor operating range on the new Cool 125 the cooling system is good. As mentioned i make scrounge up some brass tube to make two heater hose Tee for cold recirc in the engine. The idea sounds to simple, not sure why i didn't think of it 14 years ago when i first put this engine together.

A/C, still not happy. Fri trip was 90% 70 mph, near 90 degrees running on Bi-level, medium, 46 average. Best we could do was 42 on Max blower on high at 70 mph. Today it was much cooler ambient in the AM and we took the 45-55 mph route home through the woods. Bi-level, medium fan getting 46 is very comfortable but should have needed to back off on the full Cold setting but didn't.
Bill, my copilot, who has played with a little A/C in his lifetime, both he and I think the next step is remove a little more 12 from the system and raise the Superheat temp from 10 to 12 and see what the result is. One thing we both noticed as we hung out in the hotel parking lot with the car off was how long and how much water was laying in the parking lot under the evap drain. This is probably an indication the evap is frosting over and reducing efficiency. So nothing to loose by upping the SH.

Pretty sure it's not a question of the evap drain being clogged, was in there years ago and cleaned both drains and the insides of the evap area. The wife was using the car as a daily and her parking space at work was under pine trees. Those short little needles got through the cowl screening, down to the drain holes and eventually became a problem. Even her new 02 SS would clog the drain holes in the door over time with pine needles and would need to clear those drains. Even had to clear the blockage in one of the sunroof corner drains once. By the way her bosses had the parking spots with no needles.

Second temp probe for the Fluke VOM should be here soon, Will try to get an accurate idea on how the evap is performing and hoping to dial that in soon.

For a 600 mile trip didn't do a real gas mileage check. Do know it was 600 and consumed right around 30 gallons of gas. Not terrible for a big cubic inch with 4.11 gears, running A/C the majority of the time. I did tweak the cruise A/F setting a tad leaner before we left but at 72 mph cruise speed was seeing 14.6 A/F average. I shoot for 15-15.1 for those long haul drives but fuel mileage didn't suffer much at 14.6, and cruise control helps, especially with a 6 spd. .
Had to stop for gas on the way home today and pump in some Sunoco 93. OUCH, $4.099. Gotta love PA.
Bob

#1071956 - 09/06/21 06:47 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Wouldn't you know it, took my two grandsons to two car events on Sat. At 7 am and after dark needed the heater, no A/C, windows could actually be down today.
Sat was the Duryea Days show and sat evening was the show downtown, near 700 cars there.
But no real evaluation of the A/C on that day. Will be taking the car to Cecil County Dragway this Sat for the Buicks event to look at GNs and GSXs, also will make a couple passes down the track to see if the new 200 wear tires stick any better than the 6 year old rubber.

As far as the cooling system goes it's dialed in again, working great. Just so i have new parts on hand for the plug on the fan that failed a new plug and extra female terminal are in house.

Relating to the adding a cold coolant recirc to this engine.I found only one place, Australia, to buy a 5/8x3/8x5/8 and 3/4x3/8x3/4 brass barb Tees and they are salty and used in certain applications, it's an odd combo of hoses. Looking at sourcing the brass rod to make them on the lathe also.

Had both temp probes taped and insulated to evap, inlet and outlet, to monitor temps and compare to the PT numbers on the low pressure gauge. Played with charge a little but ran out of time doing the procedure and will start over again this week looking for that optimum SuperHeat number.
Bob

#1071973 - 09/07/21 11:38 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Its still warm here in Tennessee but like you said its decent in the mornings and nights, I really like this time of year due to the cooler weather but I also dislike because old man winter is getting closer and closer. I bet the grandkids have a good time out and about in the monte.

Let's us know how the tires hook on the dragstrip.

#1071980 - 09/08/21 01:10 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Well Bob, Personally, I think you are over thinking the situation with the A/C proper charge. Yes, they teach the superheat theory during training, but in the long run automotive wise, it's much simpler than that. Household HVAC, it's more critical and no I don't do HVAC. At my work, we had to check the A/C system and if the charge was low, we did leak checking on the system, pressure switches were our biggest problem on diesel engines that shake everything attached to it, recover what left, replace the switch, evacuate the system and see how much oil was removed, calibrate the same amount into the oil charge system on the charging station and inject the oil first and then the proper measured amount of refrigerant that is on the system label. JMHO, no real magic there!


Leo Paugh
It's not an attitude, it's just the way I am.
POW*MIA
You are not forgotten
If things improve with age, I must be approaching magnificent. thumbs
#1071984 - 09/08/21 05:16 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Leo you are right, with lots of time to over think things I find I still want to know the how and why of things. And unfortunately don't have one of those fancy machines to service A/C. When the system was all cleaned out, new compressor and parts, 7 oz spread around correctly, a weighed amount of 12 went in. What happened was the scale and I weren't on the same page, and a 1/4 lb to much went in. Rather then evac again, the scale and vac pump went back to their owner prematurely, I decided to play the game with finding optimum performance the hard way. Don't get me wrong, the A/C works very well, just think as us tuners do, try and get the most out of what we have. And as said an education of A/C was in order.

Funny you mention doing the system by the book. When you study the pages in the HELM'S about the system you can easily see that the parameters for a performance check are large, temps out the vent between 38-46, pressures, cycles per minute, good to go if you fall into those parameters. Have several different Helms for several GM vehicles, no specifics, just parameters.

Saturday going to Cecil County for the Buicks event, GNs and GSX cars are cool, will make a couple passes on the car to see if mph hasn't lost a step. Bolted the new 200 wear, RT660 tires back on the car to see if they will actually hook a little better and get sub 2.0 sec 60' time.
One thing I always appreciated was on the 60 mile drive back home after a hot day at the track was having cold A/C after being in the sun all day. Will monitor the vent temps on the way home. Won't be long before A/C will be off for the cold days ahead. That will put a damper of any final tuning of the system.

Have found the necessary brass 1" round stock to make the brass Tees for a bypass feed to the water pump on this engine. No hurry to get that done, just another evening of sitting next to the lathe and whittling them out. Hardest part is boring them, finding the necessary tooling. I made a bleeder Tee for 3/4" hose several years ago, installed that at the highest point in the system, heater core exit. So not a big deal making a 5/8 and 3/4 Tee now.
Bob

#1071987 - 09/08/21 08:03 PM Re: Why now, A/C R&R [Re: mmc427ss]  
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Yep, it helps big time to have the machines at your disposal at all times!


Leo Paugh
It's not an attitude, it's just the way I am.
POW*MIA
You are not forgotten
If things improve with age, I must be approaching magnificent. thumbs
#1072062 - 09/20/21 05:39 AM Re: Why now, A/C R&R [Re: mmc427ss]  
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Made the 60 mile trip to Cecil County Dragway last Sat, it was packed, took 1/2 hour just to get through the gates, another 1/2 hour to find a place to pit my friends truck and trailer. Have been to Cecil maybe 10 times and never saw the pits that full. It was a Mandra events so those cars were there but the Buick event drew a large number of Buick cars, many of them A bodies in the form of fast race cars. Close to 50 GNs including, 2 GNX (one with 1500 miles on the odometer), a 1/2 dozen T Types (my favorite), even a 68 Chevelle station wagon with a GN engine swap, and two 89 Pontiac GTA with the turbo Buick factory installed. Of all the 3rd Gen F-bodies those 89 turbo Birds are my favorite 3rd Gen.

Finally they called for T&T after lunch, it's been two years since last making a pass and have no idea how the new Falken RT660 will behave. A 2 second dry burn, stage, and spins at the launch, spins in 2nd, mind you this is granny shifting, then in 3rd gear the car fall on it's face to the lights. What the heck, 14.2 @102, crumbled that time slip up and tossed it in the back seat. Two hours later and a cheeseburger, 2nd pass time, wussy (polite) foot it this time and a 60' of 1.93, 12.92 @112 and the car made a clean pass through the lights. Last pass was in the heat of the day, 3:20, car ran pretty much the identical pass but with a .2 slower 60' so 13.1. another 112.1.

With only three runs not enough passes to really figure out the launch. And I didn't push the engine, and a 10 mph head wind. My friend 69 Camaro ran a 11.9 @112, it's a street car with a drag race setup, 2 tenths slower that day, by the way it has a 327". Typically I'm in the mid 12s with street tires, 114 average on clean passes. For me drag racing is about mph as the measure of how is the car running. Weighing the two passes I'd say it still pull hard in 3rd and 4th and hasn't lost much of a step in the 15 years since putting it together. Just the old man isn't a sharp as he used to be.

About the cooling system and A/C. New fan controller is back to being seamless, rock solid temps. On the way to the drags ran the heater for a while, didn't need A/C in the morning. On the trip home in the late afternoon, low 80s and the sun was hot found I wasn't getting good air flow out the dash vents, Hmmmm. The interior was comfortable running Bi level but not annoyingly cold. A few days later found time to look for a reason for low flow from the vents. Did the usual, check ground path to blower for loss, voltage to blower, all good on the original motor. But while testing, engine off blower running, felt air leaking from seal at the evap exit from the suitcase. Fixed that and big improvement in vent flow. If that foam seal pushes out again I'll put a dab of RTV to hold it in place.

With some time to spare decided to check the heater-A/C vac system. Pulled the vac hose off the vac reservoir and hooked the Mightyvac to the system at the ball. I had done this a month or so ago and could pull and hold a 15" vacuum on the system. This time a zillion pumps and wouldn't hold a vac. Hmmm.Behind the glove box door is access to the valve that controls outside/inside air circ. That valve good, air door functioning and sealing perfect. Above the gas pedal is the valve for dash-floor direction, it also is working and sealing perfectly. The valve for defrost is way up there above the dash-floor valve, didn't have the desire to check that one yet.

I suspected the leaking was in the rotary vac control switch now not seating. Had been moving the selections a lot while testing with the engine off, using MightyVac and couldn't pull a vacuum. Started the engine and instantaneous application of 15" vacuum seated the rotary switch, all selections worked fine. Shut the engine off and waited 15 minutes, pull the hose off the vacuum reservoir and still had lots of vacuum. It's high vacuum that keeps the rotary switch happy, sucking it together to make the seal. So that 35 year old vacuum systems seems to be okay.

While the hood was up pulled the blower motor, checked all the connections, removed and washed the blower wheel which was actually pretty clean, blew the dust out of the motor, armature/brushes well used but still serviceable, four vent holes in the side of the motor allows that. Used the MightyVac to activate the outside/inside air door to check for seal, good. A lot of the evaporator can be seen now, used a shop vac to suck out two or three small pieces of debris laying at the bottom front of the core, the core was still looking good since the last seeing it 15 year ago when the heater core was replaced. Nothing laying in drain area under the blower.

Reinstalled the blower motor, and feel things are as good as they can get for now. Maybe a new motor may spin a little faster on HI, maybe.
Will do more pressure and temp testing on the A/C system now that ambients temps are much cooler, 70s , in the coming week.

In process of modifying the cylinder block coolant bypass system. Currently with the Dart block all bypass coolant comes through the thermostat when the engine is cold and heater is closed. With three 3/16" holes in the thermostat to supply bypass water to the pump to much flow is going to the rad and engine wamup is slowed a lot. Making an H pipe that will be installed between the heater hoses so when the heater valve is closed coolant will flow out the intake and directly into the water pump inlet side. Was going to machine brass and make the H but have now changed to making it out of stainless tubing. A 12" piece of 3/4", 5/8" and 1/2" all .065" wall was ordered tonight. Using stainless will allow the H to be TIG welded, the brass would need to be soldered, didn't trust the possible stress on a solder joint with minimal contact area. A bead roller to do two 3/4" and two 5/8" beads on the tubing will need to be made. The guy that will TIG the H together said he can TIG the beads on the tubing but I will try to roll them on first. .065" stainless tubing will be very difficult to bead with a homemade bead roller but I've got lots of tubing to play with.

Registered for another Sat, Oct 2, of 16 autox runs today. It was three months ago at the last autox that the overheating reared it's ugly head. It will be much cooler that day, and i believe the overheating problem has been solved. Also planing another trip to the drag to make passes on Oct 15 or 16. These will be the last events of the year as the doldrums of the Winter season set in.
Bob

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