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Please help me, my engine is producing a very loud POP spiratically during idle and even more when the throttle is being depressed...the sound is coming from the back of the engine near the distributor. it also sort of pings through my exaust when this occurs....it sounds serious! please help me..

the engine is a 355

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'69 SS 355/350 red w/ white Z28 striping
 

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Discussion Starter #3
I'd also like to add to my problems...my plugs keep fouling and it appears that they are covered in oil..or gasoline (smells like oil) could this be the piston rings? or is my carb not set right (air/fuel) i never did have this set right because i dont' have the tools...maybe someone could tell me how many turns out the air/fuel screws should be on a 355 motor with a holley 600vs carb..it also has the performer RPM manifold and a comp cams split dur. cam

any help would be appreciated...
 

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If the mixture gets too lean you can get a lean backfire up the intake. Also this can happen if you have an intake valve that's too tight.
However, my best guess is that your intake manifold gasket is leaking, probably sucking oil and air in from the valley area. The leak is probably on one or two cylinders maybe near the distributor.

On some intake manifolds the bolt holes on the ends are smaller than the other bolt holes. when you tighten the manifold down, it sits lower and lower as you tighten the manifold bolts, eventually the corner bolts can bind and stop the manifold from coming down any more.
Manifold misfit is caused by milling the block and heads and causes the intake surfaces to move away from the intake manifold faces.
The solution is to get special thicker intake gaskets.
If I were standing there listening to it it would be a lot easier, but that's my guess.
Try spraying a little window cleaner or water around the manifold and carb base while it's running and see if you hear a change. Slurping or difference in speed would indicate a leak. Of course you could have a leak on the bottom of the manifold only, that wouldn't show up.
And, if your carb is very black inside you are getting backfiring.
David

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The older I get, the faster I was!

[This message has been edited by davidpozzi (edited 06-03-2000).]
 

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Sounds like a broken rocker arm ,or a worn lobe on the cam, pull the rocker covers and check the arms first, If you find an arm that is loose but not busted up then the cam and lifter may well be shot. OUCH can be costly.
 

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Rob, You are probably right. What I was suggesting would probably not make a really loud pop.
I saw a corvette with a flat lobe on the exhaust, it cause the intake stud to pull out of the head about a half inch because it was being opened against the remaining cylinder pressure. It really popped, came out of the carb though.
David

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The older I get, the faster I was!
 
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