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#1051231 - 06/04/17 04:04 AM Re: Need input on crankcase evacuation remedies [Re: SSLance]  
Joined: Jan 2000
Posts: 3,604
mmc427ss Offline
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mmc427ss  Offline
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Joined: Jan 2000
Posts: 3,604
Pottstown, Pa
Haven't called Dave at MM yet, figured I needed to know what the new catch can system is doing before call was made.

So a test of what's going on in the crankcase is being done from cold start to hot idle over a 15 minute period. The MM can is disconnected from the engine. At the dirty side valve cover exit a hose runs to an improvised catch can. This is a 16 oz clear plastic water bottle with a 3/8" barb fitting epoxied 3" from the bottom. It is stuffed with two steel scrubbies for washing dishes, this mimic the material used in catch cans. The cap of the bottle is left off, this is the breather for the plastic can. Dirty air into the bottle, hopefully catch vapors and liquids, stinky air out the top. The clean air intake in the other valve cover is plugged with a vac/fuel pressure gauge. The dipstick tube is now adapted to input compressed air into the crankcase.

The procedure is apply 1 psi of air pressure to the dipstick tube. The gauge will show only a slight deflection, you feel the air pressure exiting the top of the plastic can. Do a cold startup, choke and all, idle engine until it's cycled the electric fans at 190, then run several minutes longer to hopefully get the oil up to 180 degrees. All the while doing a visual of the bottle and it's vent looking for, something? Have run this test twice and got, NADA. Sniffing the bottle vent tells you it's blow-by, doing the smoke test of the stream says the flow is slow and steady. But no water or oil in the bottle. At the minimum there should be something showing in the CLEAR plastic bottle.

Have run this test twice now, a few more times will happen. It takes about 1 minute to swap back and forth between the systems. Will run some hot tests also, go beat on the car and then do some hot hot idle testing. If an air pig was strapped into the pass seat a few WOT runs could be made at 1 psi to see what shows up in the plastic bottle.

At this point one thing stands out, how little blow-by this engine makes. With both dirty air and clean air ports wide open in the valve cover you see nothing at idle, yes it sticks, but that's expected. I've had a few SBC in my days, they all had something to show.
Possibly the end result of the catch can on this large displacement Q-jet SBC is the can won't be needing emptied very often. Disappointing because I wanted something to look at, bummer.

Once I figure out how much vac to apply at the new PVC, install the clean side restriction to maintain a few inches of vac at idle, I'll move on to something else. Opening the can drain periodically to see what's there should tell the story.
Bob

#1051252 - 06/05/17 03:51 AM Re: Need input on crankcase evacuation remedies [Re: SSLance]  
Joined: Jan 2000
Posts: 3,604
mmc427ss Offline
15+ Year
mmc427ss  Offline
15+ Year
Member

Joined: Jan 2000
Posts: 3,604
Pottstown, Pa
Ran another cold start test yesterday, nothing. After reinstalling the MM can had the car car out yesterday and today, maybe 35 miles of just cruising around, the wife was with me. The engine does seem more responsive, this due to eliminating the large vac leak the stock PVC valve produced.

On the trip back to my shop this afternoon gave the engine a good workout. Parked it, hooked up the plastic catch can and blew 1 psi of air through the crankcase with the engine hot and idling. Got nothing in the can and if you caught the blow-by exiting the top of the bottle in the right light you could see a faint hint of blow-by. Ran it for several minutes, two cycles of both electric fans running On and Off, the second fan doesn't come on until about 195. So catching blow-by in the plastic can showed me nothing.

Next reinstalled the MM can. installed a gauge on the dipstick tube. Left the clean air wide open and got no vac on the dipstick tube.
Next plugged the clean side air port, 3 1/2" vac at the dipstick.
Next installed my restricted clean air fitting at the clean air intake. Currently a .048" hole. The vac reading at the dipstick tube slowly increased to 2", this on a hot engine idling at 750 and 13.9 A/F. Another vac gauge reading manifold vac reads a rock steady 16 1/2". So currently seeing 2" vac on the crankcase.

After letting the engine cool for a while opened the drain on the MM can, not surprised, nothing came out. Hmmm?

Got enough info now to have a talk with Dave at MM. Need to know what to expect if I increase his orifice size in the MM PCV valve. And If he will sell me another valve if I screw it up. I think with the engine build I'm working with a little more crankcase vac won't hurt anything. Shooting for 4" at the clean air intake. Will install a barb fitting in the restricted clean side to monitor PVC system vac. No big deal.
Bob

#1051434 - 06/12/17 09:11 PM Re: Need input on crankcase evacuation remedies [Re: SSLance]  
Joined: Jan 2000
Posts: 3,604
mmc427ss Offline
15+ Year
mmc427ss  Offline
15+ Year
Member

Joined: Jan 2000
Posts: 3,604
Pottstown, Pa
Brief update.
A barb fitting to hook a vac gauge to the now restricted clean air side of the system is done. This allows monitoring of crankcase vac or pressure real time while driving. Will log a lot of miles this month, including a 200 mile round trip to Carlisle on the Pa Turnpike at 70+ mph. Won't have an opinion on what's going on with the recalibrated PVC system till the end of the month. Have made several trips over the years in this car running a tank full or more and checking mileage. Using the cruise, A/C on and some music almost 20 mpg is the norm. One of the suggested claims for a catch can system is increased fuel mileage. Don't think you would notice it doing around town driving. But because you don't have that large vac leak in the intake it may require less fuel at highway cruising. Remember I had to lean the idle A/F out when the catch can was installed, and cruise at 60 mph also needed to be leaned from 14.6 back to 15.0

Changed out the PCV valve grommet on the valve cover. The piece of crap Dorman HELP rubber grommet was swollen and very soft, just another junk product from them. The GM 14091870 grommets only come in a 5 pack, now I have a few spares. The clean side valve cover did have that GM grommet installed there for years, it was still good, but changed because I bought 5.

Spoke to Dave at MM last week, couldn't give me a definitive number on crankcase vac needed, but having just enough to keep a slight negative pressure at idle was suggested. So I'll play with slightly higher idle vac after I see some data oh what he would run, which is how the system is calibrated now.
Bob

#1051575 - 06/19/17 03:03 AM Re: Need input on crankcase evacuation remedies [Re: SSLance]  
Joined: Jan 2000
Posts: 3,604
mmc427ss Offline
15+ Year
mmc427ss  Offline
15+ Year
Member

Joined: Jan 2000
Posts: 3,604
Pottstown, Pa
Another brief update.
A vac gauge now in the restricted clean air side, and a vac gauge monitoring engine vac. Idling 16" engine vac, about 1 1/2" on the PVC clean air side. A 4 mile trip around the block monitoring both gauges showed less than 1" at cruise or light accel, of course on high vac reading during deceleration that would climb very briefly to almost 2".

Back in the shop removed the PCV valve from the can, it's orifice was .199", so with a .048" restriction in the clean side 1 1/2" at idle.
Got out the number drills, opened up the valve to .205", now 3 1/2" at idle with a .048" restriction.
Next with the .205" valve install a .099" restriction, now 1" vac on the clean side.
Next opened up the valve to .209", with the .048" restriction now 4" vac on the clean side.
Next with the ,209" valve installed a .099" restriction, now 1 1/2".
Next with the opened up PVC valve orifice to .209" (.010" larger than stock) and a .059" restriction in the clean side 3 1/2" vac on the clean side.

So I increased the PVC valve orifice area by 10%, .199" to .209", and restriction area by 56%, .048" to .059". Just hard to imagine a .059" hole can flow enough clean air into the engine, but that's what I've been told.


That was the target I was shooting for, 3-4" at idle. Another test drive to see what the numbers are during various phases of driving will determine if I have gone to far. One thing I did notice was the A/F at idle got a little leaner after the final configuration was done. Something to think about, more tuning to follow. Removing the dipstick from the engine dropped crankcase vac to zero real quick. But putting your figure over the dipstick tube and it's right back at 3 1/2", and you can feel light suction on the tube. A good indicator of what's going on in the crankcase.
Bob

#1051703 - 06/23/17 05:34 AM Re: Need input on crankcase evacuation remedies [Re: SSLance]  
Joined: Jan 2000
Posts: 3,604
mmc427ss Offline
15+ Year
mmc427ss  Offline
15+ Year
Member

Joined: Jan 2000
Posts: 3,604
Pottstown, Pa
Got the second clean air pipe powder coated on Tues, the last of the pieces to this puzzle. After having a vac hose barb welded into the first tube i made it was destroyed when I tried to wash the anodize off with Muriatic acid. Moral of that story is don't go eat diner while the alum tube get ate from the inside out. Also glass bead the tube, acid doesn't remove anodizing in some cases. although it did work on Aeroquip fittings, hmmm.

Dialed in the idle A/F at 13.9, 800 rpm and see a consistent 3 -3 1/2" of vac on the crankcase. Having R12 A/C and dual fans the engine was ran through a dozen circles while checking the tune, very happy at this point. Took a spin around the block and it shows the same vac under most conditions. When vac increases significantly under heavy decel, +20", crankcase vac will increase to 4 1/2", that was expected. That is probably good to add a little more purging for a carbed engine at that time, a lot of junk going past the rings under hard decel.

Hard to find somewhere to test WOT for a good distance, like a mile, around here anymore. To many people with cell phones these days. With this MM recirc can the cleaned positive pressure at WOT from the crankcase goes into a white filter in the air cleaner base. It's very easy to monitor what get dumped at that filter under WOT driving, I'll keep an eye on that. The old clean air side had the same filter, I would monitor that for how much oil was being pushed out there when it was the the positive crankcase pressure relief point. Over a period of several months there would be a very light oil mark on the filter, nothing drastic.

The last thing I did to the system was drain the can, got maybe a teaspoon of water out of it. Doing a 200+ mile round trip this weekend to Carlisle, most of it will be 72 mph, will be able to dial in the cruise A/F, 15.0. It takes about 2 minutes to tweak it on a Q-jet. With A/C on, CD cranking, and cruise set at 72 looking for 20 mpg with the 4.11s. Of course when i get back I'll be draining the can again, hopefully it catches something that would have went down the intake runners.
Bob

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