Hey, I have a 91' camaro RS with a 305 tbi. I had shorty headers, 2.5" y-pipe, no cat, 3" test pipe, and 3" flowmaster w/ 80 series installed recently. Anyways, when i start the car when its cold and rev the engine (but i have to bring it to about 3500 rpm then let go of the throttle fast) a popping sound is heard throughout the exhaust. it sound really bad. I noticed during an oil change over the week end that my passenger side header is away from the cylinder head by like an 1/8th of an inch. and i could feel the exhaust coming out of the space. so i thought that when i accel the exh. speeds up in the header tube creating a vacuum as it goes down to the collector. so i thought the vaccum, being low pressure and the high pressure ambient air creates a pressure differential and draws in the fresh o2 rich air. since the engine is cold the pulse width of the injector is longer=more fuel. the fresh o2 mixes w/ the unburnt fuel in the exhaust burning it throught the system. whew!! can that cause damage if the pressure gets too high. and the header bolts in the front of the engine were acutally loose when I looked at it!! but the ones near the firewall were tighter. There is a torque sequence, right? i'm guessing they cocked it when torqueing it or maybe bent it . should i try to retorque it? and see if it pulls it in, or if that doesnt work will 2 gaskets do the job? ok, thank you all in advanced.

 

Duh? last time i looked at a manual all the engine parts were supposed to fit together tightly at the joints.
headers have to actually bolt up directly to the heads. it almost sounds like you torqued them down one bolt at a time instead of screwing one down finger tight, then doing all of the that way, and then using a torque wrench and tighten them in the order stated in your manual.
if you bent the header it needs to be fixed, or you will never get it right. you cant fix a bent part by adding a gasket.
unbolt the entire thing, take it off, see if it is flat and if it is start all over by tighting in the order the manual says to use for you car. and get a new gasket for that side. used gaskets dont work so well.
good luck.

 

I had the headers and exhaust installed by someone else they didn't do a great job. I'm going to try to retorque them. If that doesn't draw them in I'll take it apart and check out whats going on. The spec for them is 25lbs-ft. Thank you.

 

Also, check the timing. If the timing is retarded too far, you could blow out the gaskets.

 

Hey, thanks for all your comments. They helped. Today I think I found the problem. Where the header is welded onto its flange, it goes thru the flange then its folded over and welded on.I can feel the exhaust coming out from there with my hand. I should try to braze it, if it's not too bad, right? But can I do it in the car(I've brazed parts while inside the car before) or would it be better to take it out first. I guess if i take it out I can check if there is any other problems.
Thanks.

 

Hey, now I found it's not the headers at all. I was looking into the engine compartment as someone revved the engine, and I actually saw flames come out from between the two center cylinders on the passengers side, when he took his foot off the throttle quickly. But it looks like it's coming from a lower point, like from where the cylinder head meets the block. I know from this the head gasket is completely shot. But does anyone know what those heads are made of(it's a L03 5.0L, stock). If there aluminium maybe there warped but if there cast iron they will not warp but crack instead. I'm going to pull the head and check it out, but if anyone can help, what should I look for. Alumininum I'll put a stright edge on it with a feeler gauge. But if it's cast iron and if it's crack how can I find that. Is there anything elese that could be wrong? If anyone has had a simiular problem could you let me know of any tips or advise? thank you all.

 

The stock LO3 heads are iron.