I put a set of Dynomax ceramic headers on my 454
two years ago. Since then, I have a ripping sound that seems to come from the drivers side by my left foot. Just about right over the collector.
It starts at around 4500 rpm and goes until I shift. Only does it when I am really on the gas.
Sounds like someone taking an air chisle to piece of sheet metal. I have tried to see where the headers could be hitting the frame, but the closest place is still 3/4" clearance. Could this be a too lean condition causing some "crackling" or severe popping in the collector? Have I been looking for the wrong cause?
any opinions?

Dave

Dave, it's likely not this, but I would sure pull my valve covers and check every spring with a flashlight.

It's an enigma for sure.

It might be that the torque when your "really on the gas" is lifting that side of the engine and there goes your 3/4" clearance. Are you running rubber mounts? We found it necessary to run Energy Suspension Poli Mounts on our 66 and Morosso steel mounts on our 65 that are both running 454's

Gene, are you suggesting valve float from broken springs?

Rick, I am running rubber mounts. They are the GM
locking type that supposedly only allow a small amount of travel before it locks. I thought about this, but did not want a solid mount there. I suppose I could tape a piece of paper over the frame in that spot and take it out and get on it.
If the paper has a hole rubbed in it when I get back it will answer that question once and for all.

I was really asking what it sounds like in the collector if the engine is too lean.
I got a performance meter from Escort and when I was working on 60 foot times, the car was bogging.
fixed a float level problem, but still bogs on occasion. I am thinking it is because it is lean and that may also be causing my ripping/crackling in the collector. Not sure.

I'd be sure to check the clearance between the fan and fan shroud. When you installed the headers, you most likely had to jack the engine up a bit. When you lowered it back in place, it may not have settled back into its original position on the mounts. An engine can be moved around a bit when it's sitting in the frame, and it may have shifted just enough to cause the fan to bump the shroud. I'd inspect the fan blades very, very closely also. You may have a blade with a hairline crack that is vibrating at high engine speeds.

I never thought about the shroud Randy.
That is possible.
I'll take a look.
Should be some marks on the inside of the shroud
if that is what is happening.

Thanx guys for the input.

Are you sure the headers aren't rubbing the steering shaft? Look for marks on both. Seems to be pretty common with BB's and headers.

Originally posted by von:
Are you sure the headers aren't rubbing the steering shaft? Look for marks on both. Seems to be pretty common with BB's and headers. Postitive they are not.
1 3/4 inch headers are at least 1" or better
away and no marks.