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#1069816 - 03/09/21 06:02 PM Rough under load  
Joined: Jan 2008
Posts: 1,199
FinallySS Offline
10+ Year
FinallySS  Offline
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Joined: Jan 2008
Posts: 1,199
Nice Sunny Hawaii
Aloha guys.

As we speak, I am searching the web and see if I can find what I'm looking for but in the meantime, I thought I'll pick your brain(s) for a while.

Just yesterday, my SS was running beautifully. Problem started when I stumped on the gas to merge on the freeway. I took it up to maybe about 4500 rpm max (after about 3000 rpm, car trying to catch up or chase waaaaay behind me gave up. Kids nowadays never seen a old American car, so maybe they thought another grandma driving old American car?). After that acceleration, my car started to run really rough. Almost feel like it's starving for fuel as I give it a gas, still rough but gets little smooth and start to accelerate. For rest of the day, condition never improved but at any moment, idle is very smooth. No load rev, even when I give it a gas, will rev freely without any roughness. Fast forward it to today, cold engine just refused to accelerate. Still idles very smooth.

My combo for this engine is Eddy 600 carb (without choke), Summit 1102 cam (this one. https://www.summitracing.com/parts/sum-1102/make/chevrolet), Summit valve spring kit (https://www.summitracing.com/parts/sum-174000), Mid-length header (I know it's Hooker, but don't have the part # as it came with the car. Full headers in near future), El-cheapo Chinese dizzy (adjustable advance vacuum can), Accel 8.8 wires (need to change soon), Brand new Spark plugs (I think it was ND Iridium. Just wanted to try out something. Since it's new, I have no plan to change it any time soon), Summit ignition box (https://www.summitracing.com/parts/sum-850610), 1-inch carb spacer (Can't remember if it was square to Q-jet or just square, but it's open spacer), K&N filter and full dual exhaust (no cat. Don't blame me. Car came that way!).

Now, when I came home, I checked that, timing is OK (initial 12 degree, hooked up to manifold vacuum), Plugs were all OK (no excessive carbon build up. I'm still playing with carb jetting), made sure step-up piston is not stuck (moved freely in the bore), Accel. pump function (it shoots fuel), look into carb bore making sure nothing is in there (had filter on, so unlikely but just to make sure) and making sure carb received the fuel it need (pump is working but I do not have pressure gauge at the moment). I do not have any method of checking the plug wires so left it alone for now. I'm planning to take the carb off in a few hours and give it a good cleaning by disassembling it. I do not have rebuild kit in hand and will be using old gasket until it gets here (It is on the way. Order it last night just in case). I just hope that weather stay clear of rain (it's very dark and cloudy right now).

Now, for what I done recently is I removed the intake because it had oil leak from back of the intake (I didn't put enough RTV last time I had it apart) and while I'm at it, took both cylinder head off and changed the valve springs. I did adjust the preload on lifters, but I'll gonna do it again just in case if cleaning the carb won't change anything. No vacuum line to check other than the line going to vacuum can on dizzy and to the vacuum ball. Both checked out fine as I have vacuum pump with gauge on it (cheap one, but it'll do the job for now).

Anything I'm missing? Any suggestion? My DD is still in repair (waiting on one rear wheel bearing I bought back in 2/21/21. According to USPS tracking, it made it to CA on 2/25/21, and it move from there on 3/1/21 as it said still in transit, but I still haven't receive it yet. USPS said because of the snow storm you guys suffered, but in CA? To this day, I'm still waiting for it.......................) so I need my SS going again.


1986 Silver MCSS - Poly bushing and Hotchkis spring w/Bilstein, Posi w/3.73, MSD 6-AL, E-Brock 600cfm, Aluminum 2-row radiator.
1986 Black MCSS - R.I.P............Finally.
#1069820 - 03/09/21 07:39 PM Re: Rough under load [Re: FinallySS]  
Joined: Mar 2000
Posts: 5,655
upflying Offline
20+ Year
upflying  Offline
20+ Year
Member

Joined: Mar 2000
Posts: 5,655
Reno, NV
Mine ran like this after sitting for 6 yrs after my initial stock restoration. Turned out the fuel line from the tank was plugged/clogged with stale gas fuzz. I think you answered your question, sounds like fuel starvation.

Last edited by upflying; 03/09/21 07:39 PM.

86 MCSS Notchback coupe, LS3, 4L65E, QP 9", Eaton Truetrac, 4 wheel disc, column shift, Dakota Digital, silver with maroon bench interior

#1069821 - 03/09/21 09:10 PM Re: Rough under load [Re: FinallySS]  
Joined: Feb 2020
Posts: 566
88ssBrent Online content
Member
88ssBrent  Online Content
Member

Joined: Feb 2020
Posts: 566
Friendsville
Mine had the same symptoms. It drove me crazy. It ended up being the fuel filter clogged. Of course mine is the factory quadrajet. Changed the fuel filter at carb and everything was fine.

#1069823 - 03/09/21 11:27 PM Re: Rough under load [Re: FinallySS]  
Joined: Feb 2008
Posts: 909
AkronAero Offline
10+ Year
AkronAero  Offline
10+ Year
Member

Joined: Feb 2008
Posts: 909
Akron OH
Or check for failed or cracked dist cap or shifted ign?

#1069825 - 03/10/21 06:57 AM Re: Rough under load [Re: FinallySS]  
Joined: May 2007
Posts: 5,045
Buick Runner Offline
10+ Year
Buick Runner  Offline
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Joined: May 2007
Posts: 5,045
Dharma station 1 the Hydra
My tractor does this once a year when the needle valve from the previous year begins to stick and strave the engine at wide throttle.


SBC powered 1987 Regal with TES headers, ZZ4 intake, ZZ4 PROM chip, mini starter, THM2004R, 2500 stall converter, 2040 cam, CCC system, and 3.73 posi rear.

2008 ex NPS P71 Crown Victoria, cop motor, cop shocks, cop brakes, and Jmod.

Never argue with an idiot.
They will just drag you down to their level and beat you with experience.
#1069826 - 03/10/21 07:22 AM Re: Rough under load [Re: FinallySS]  
Joined: Jan 2008
Posts: 1,199
FinallySS Offline
10+ Year
FinallySS  Offline
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Member

Joined: Jan 2008
Posts: 1,199
Nice Sunny Hawaii
Thanks for all the advice guys.

Finished cleaning the carb, look at the plugs, check ignition wires for physical damage and all the other stuff. Because of the weather, couldn't do much and I'm all tired. test drove it up and down the driveway ramp and the roughness went away. Will drive it to work tomorrow and see how it goes. Couldn't find any obstruction while cleaning carb, but shot all the passage with either carb cleaner or Brakleen (used both. carb cleaner ran out), so hopefully, if there was any obstruction, it did clear it away.


1986 Silver MCSS - Poly bushing and Hotchkis spring w/Bilstein, Posi w/3.73, MSD 6-AL, E-Brock 600cfm, Aluminum 2-row radiator.
1986 Black MCSS - R.I.P............Finally.
#1069837 - 03/10/21 05:00 PM Re: Rough under load [Re: FinallySS]  
Joined: Apr 2011
Posts: 1,200
Hunter79764 Offline
10+ Year
Hunter79764  Offline
10+ Year
Member

Joined: Apr 2011
Posts: 1,200
Grand Prairie, Tx
I'd suggest some SeaFoam as well, it might get a few more places than the carb cleaner did. It would also keep whatever was gummed up from gumming up again if you use it periodically.


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
#1069847 - 03/11/21 03:53 AM Re: Rough under load [Re: FinallySS]  
Joined: Jan 2008
Posts: 1,199
FinallySS Offline
10+ Year
FinallySS  Offline
10+ Year
Member

Joined: Jan 2008
Posts: 1,199
Nice Sunny Hawaii
Thanks hunter for the advice. I'll grab some when I have a chance. Long overdue, in my opinion.

Yup. Runs way better than what it was, but still not the way it was running. One thing I forgot to check is fuel filter, so I'll definitely check first chance I got (raining outside now).

Maybe something got loose and clogging the fuel system. I need one whole clear day...................


1986 Silver MCSS - Poly bushing and Hotchkis spring w/Bilstein, Posi w/3.73, MSD 6-AL, E-Brock 600cfm, Aluminum 2-row radiator.
1986 Black MCSS - R.I.P............Finally.

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