Big Block running poor
Thread Starter
Racer
Joined: Jul 2007
Posts: 269
Likes: 0
From: WV
Big Block running poor
Having a problem getting my 454 running right again after putting a distributor in. The motor is having a lot of popping through the exhaust while coasting that it did not have before. It also seems like it is having a hard time while moving at very low speeds its like chugging around and seems to lack off idle torque. We have tried adjusting the timing in just about everydirection possible with no change in these problems.. You can hear a miss in the exhaust an when checking the header temps with an IR gun 3 of the tubes are about 200 degrees cooler than the others but when we pull the plugs all colors appear to be the same...
The crazy part is when you get on it the motor runs amazing with tons of power to boot and smooth as can be. The car also starts up easily both hot and cold.
Help please
The crazy part is when you get on it the motor runs amazing with tons of power to boot and smooth as can be. The car also starts up easily both hot and cold.
Help please
Race Director
Joined: Jan 2000
Posts: 13,017
Likes: 2,261
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Double check firing order?
What is initial and total timing set at?
What distributor did you take out and what did you put in?
Which 3 cylinders are cooler?
Any chance you knocked a vacuum line off somewhere?
JIM
What is initial and total timing set at?
What distributor did you take out and what did you put in?
Which 3 cylinders are cooler?
Any chance you knocked a vacuum line off somewhere?
JIM
Racer
Joined: Apr 2008
Posts: 436
Likes: 2
I'm also having some similar problems, except my exhaust pops on hard acceleration (i.e. only when at or close to WOT, not so much at 1/4-1/2 throttle when I'm just driving in traffic). Even with the popping, the performance is not bad, but I'm sure it could be better.
I also feel like mine is chugging, slightly jerky, etc. when I'm driving at slow speeds...about 30 mph or less sustained. It's smooth when cruising above 30 mph. My dizzy, wires, plugs are new (only about 500 mi on them). Timing is set at 6 idle and about 36 total advance (per GM specs).
Unfortunately I'm not home anymore and can't play around with the car, but know a mechanic who can tinker on it a bit for me...just want to be as informed as possible.
I also feel like mine is chugging, slightly jerky, etc. when I'm driving at slow speeds...about 30 mph or less sustained. It's smooth when cruising above 30 mph. My dizzy, wires, plugs are new (only about 500 mi on them). Timing is set at 6 idle and about 36 total advance (per GM specs).
Unfortunately I'm not home anymore and can't play around with the car, but know a mechanic who can tinker on it a bit for me...just want to be as informed as possible.
Melting Slicks
Joined: May 2009
Posts: 3,079
Likes: 315
2024 C3 of the Year Finalist - Unmodified
I'm having similar problems with exhaust popping and chugging at low speeds in 1st and 2nd, around 2000 rpm. Thinking about looking at the new vacuum advance. Right now I'm at 12 deg initial and 32 total. I'm gonna follow this thread for suggestions.
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Like most old cars, you got too play with it and give it the seat of the pants dyno. I would bump it 2+degrees until it starts pinging then back off. After that you can play with the advance curve with springs and weights
Assuming firing order and everything else is correct!
Assuming firing order and everything else is correct!
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Drifting
Joined: Feb 2005
Posts: 1,879
Likes: 38
From: Los Gatos CA
You perfectly described what happens if you have too much low load advance, which is vacuum advance. Unhook and plug vacuum advance and test drive car; I bet it goes away. You need a vacuum can with about 10* advance, all in at 2" hg below idle vacuum.
