My engine isnt running right

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JungleCrow

JungleCrow

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So this 383 B engine fell into my lap and it doesnt seem to run right. When it is running the engine rpms fluctuate. It runs like some sort of race cam where it idles high then low then high then low making a varooom... varooom... varooom... It runs so rough too. Shakes the car inconsistently. But sometimes it idles ok but like its about to die like the spark isnt there. Sometimes it picks up sometimes it dies. Its just not constant at all so Im not sure if it is a cam thing. When I loosen the distributor to mess with timing... Just loosening it make it run better. Retarding the timing made it run smoother but then it would die when I gave it gas and once it shot fire out the carb. I have a new distributor coming in to replace the ignition box style. I replaced the coil cuz it was leaking oil but that didnt fix it. Im just not sure what it is. Anyone got any idea?
 
without actually listening to it in person it could be a few things.....but id start with the simple stuff.timing,compression test,plug condition,etc.it kinda sounds like a vac leak .
 
As mentioned, vaccume leak/EGR leak though I don't think 383's had an EGR. Ck. the advance weights in the distributor for acting up or a bad dizzy.
 
I agree, sounds like a vac leak to the distributor, I'd replace that vaccuum line and the fittings before you replace the distributor, you'll never get your timing right with a leaking vaccuum advance.
 
There are no vacuum leaks as there are no vacuum lines other than the one to the distributor. There is no sounds from the manifold to make me believe there is a leak there. As far as the vacuum advance on the distributor... Im not sure how that would cause it to run as rough as it is. I mean arent you suppose to take that line off when you adjust initial timing? I mean the engine shakes real hard and when the timing is advanced on the distributor it makes the engine sound like its got some real lopey cam. The ones that sound like someone keep hitting the gas every couple of seconds. When I retard the timing it runs smoother but doesnt have power or I can give it gas or it dies. I really think its a timing thing. Maybe the mechanical springs are worn out or maybe the vacuum is going bad.

Thanks for all the help and for clarifying my questions.
 
ok,have you checked everything else like compression,spark plug condition,verified the firing order is correct,checked for a burnt/ cracked plug wire?have you tried adjusting the fuel/air mix screws?whats your timing actually set at?have you taken a vac reading ?there are alot of things it could be.its difficult to diagnose until its narrowed down a little.
 
A cracked wire sending the spark to Ground every so often..?


I had that happen once on a 911 Porsche I owned long ago.

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Everything is fine. I have not checked the compression or plugs yet as I just bought a compression tester. The coil is new. Wires are good. I already replaced a bad one. When I adjust the idle mixture screws on the Holley it doesn't affect the way it idles but does affect when I give it gas typically flooding the engine or backfire out the carb. I tried to adjust the mixture to get the best vacuum but its hard due to the problem. The vacuum fluctuates around five. When the engine revs it hits 5-7 and when it stops it goes below its very inconsistent.
Ill have to check the compression probably tomorrow along with the plugs.
 
Put a tape on balancer; Check timing from idle to 3500 rpm. Figure curve, and start there.
 
JungleCrow said:
Everything is fine. I have not checked the compression or plugs yet as I just bought a compression tester. The coil is new. Wires are good. I already replaced a bad one. When I adjust the idle mixture screws on the Holley it doesn't affect the way it idles but does affect when I give it gas typically flooding the engine or backfire out the carb. I tried to adjust the mixture to get the best vacuum but its hard due to the problem. The vacuum fluctuates around five. When the engine revs it hits 5-7 and when it stops it goes below its very inconsistent.
Ill have to check the compression probably tomorrow along with the plugs.
Click to expand...
if you establish its not a tuning issue,firing order,idle screw/float adjustment,etc.you may want to look at valve timing .
 
You said there are no vacuum leaks. How have you verified this? The best way is with a spray bottle of water. Spray all around the carb base and all around the intake manifold to head joints. I bet a dollar you'll find one somewhere.
 
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