I have a noise coming from the engine, only when it is cold. it sounds to me like the headers leaking. once the car is warm, no more sound. brought it back to my mechanic who installed the engine (one week ago), and he said he could not notice any leak (of course it was warm then). Does this sound like a header leak? I have checked the bolts, and they are all tight. Should i try replacing the header gasket? any other tricks??

it definetly sounds like a header leak the metal expands when it gets hot and seals, fix it now or it will damage the exhaust port.

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chris
1980 Z/28
(under construction)

Could also be a lifter that has pumped down and is ticking with the engine is cold and finally pumps up as the engine runs. Yes they may be new but that is all it means. An easy check for an exhaust leak is to crank it up and pour a little bit of tranny fluid down the carb. Watch for any smoke that rises from the engine compartment and pay attention where it is coming from. Any smoke other than directly out of the end of the pipe is an exhaust leak. Don't go overboard with the fluid as you will hide the neighborhood with smoke! Just guessing about a half of a cup will be enough. You may have to give it a little throttle as to not stall the engine but the tranny fluid will not hurt anything in the engine.

What wieght oil do you use? This could be the simplest problem. It might just need time to warm up before you take off. The best way to find out if it's a header leak is to pop the hood, start the car and then get up there before it stops or have someone start the car for you. If that is what is is try a set of Earl's Pressure Master Header Seals. They run about $35.99 in Summit.

Header leaks have always been a problem and to fix it, first ensure your gasket is of good quality then start the car and let it get to normal operating temp., shut it off and tighten the header bolts while their hot since they too expand and loosen when their hot. If this doesn't do it look elsewhere, could be leaking at the collector, or a valve pumping up.

68DD: Somthing else you may want to look for while checking out your headers , somthing I ran into with my 69 with a set of hookers on it . When you get the headers off to change the gaskets look at the openings of each tube and make sure that they are welded all the way around on the flanges . I had to reweld mine and now they are as quiet as headers can be, good luck.