Question: exhaust leak

[spikebot 81]

Ive been fighting a rough idle for weeks now and just noticed what sounds like a exhaust leak somewhere around the manifold. Could this small leak cause a rough idle? Thanks for any advice you guys can give me.

 

[crowvet]

Ive been fighting a rough idle for weeks now and just noticed what sounds like a exhaust leak somewhere around the manifold. Could this small leak cause a rough idle? Thanks for any advice you guys can give me.

Yeah, it can to a certain extent, usually not a very noticable difference. What happens is the engine is pulling in the exhaust into the engine thru the air cleaner. This air has a certain amount of hydrocarbons in it and the engine will run a little rich. I had a ski boat with a enclosed engine compartment 455 olds. It would run alittle rough if the manifold gaskets started leaking.

 

[spikebot 81]

Thanks Crowvet, Not sure this leak is big enough to create that much hydrocarbon. Maybe I should give more info. New edle carb and intake, new distr., no smog stuff, no ecm, new plug wires, new plugs. No vac leaks. Adjusted valve lash. I,m kinda stumped. Havent checked compression for burnt valve. Dont have the tester for that. Fuel pump has good presure.

 

[Crimson Thunder]

Are you sure it is not a vacuum leak at the intake manifold?

 

[spikebot 81]

sharkcar, Well it sure acts like it but Ive spayed starting fluid and the propane torch trick all around the intake, cant find any trouble spots. I just heard this ticking yesterday so I used a 3/8 hose for listening and picked up some ticking at the stock header manifold where all pipes come togeather. I didnt know if a slight exhaust leak would cause a engine miss or not.

 

[crowvet]

sharkcar, Well it sure acts like it but Ive spayed starting fluid and the propane torch trick all around the intake, cant find any trouble spots. I just heard this ticking yesterday so I used a 3/8 hose for listening and picked up some ticking at the stock header manifold where all pipes come togeather. I didnt know if a slight exhaust leak would cause a engine miss or not.

Did it run this way before the mods? Or did this happen afterwards? If afterwards, I would look for a cracked spark plug or valve alittle to tight.Also if it is a vacuum problem ypu can fog some carb cleaner or propane into the carb. If the engine smooths out you have a vacuum leak. If it bogs down you do not.

 

[spikebot 81]

Daryle, Engine ran like crap when I first got the car so hard to tell. Ive been thinking all along its vacuum leak. I didnt know about adding extra fuel directly into carb. I did find yesterday the pickup module in the distr. had some melted plastic spots on the housing. Called summit they will send a new dizzy monday. If that doesnt cure my idle problems Ill try flooding the carb with mapp gas. As far as the exhaust leak, found broken weld on drivers side manifold. About a 1/16 size hole. Time for long tubes. Dynamx ceramic headers will be here monday. Cant wait for that HP boost. WAHOOOOOOOO

 

[crowvet]

Daryle, Engine ran like crap when I first got the car so hard to tell. Ive been thinking all along its vacuum leak. I didnt know about adding extra fuel directly into carb. I did find yesterday the pickup module in the distr. had some melted plastic spots on the housing. Called summit they will send a new dizzy monday. If that doesnt cure my idle problems Ill try flooding the carb with mapp gas. As far as the exhaust leak, found broken weld on drivers side manifold. About a 1/16 size hole. Time for long tubes. Dynamx ceramic headers will be here monday. Cant wait for that HP boost. WAHOOOOOOOO

Thats cool, No doubt in my mind that you will have this thing purring like a scr-wed tomcat in a creamery before the good weather hits