jread199

I recently finished my 7 year restoration of my 1967 olds cutlass supreme sports coupe, and thoroughly enjoy driving it except at 50 to 55 mph. that is when I hear a constant drone from exhaust system. the motor is an olds 350 with mild cam 2 something rear gears and a 2.5 inch pypes exhaust system. below and above said speeds the sound is pleasant not distracting, unfortunately when i am cruising that is the speed i like to drive. is this something i should expect or are pypes mufflers known for this, thanks in advance.

MDchanic

You've got one of those "X" crossovers, don't you?

That's what they do.

You pretty much either have to change your exhaust system, or create and install a Heimholtz resonator, as in this post, as far as I know.

- Eric

don71

You must be in some harmonic resonant rainbow. You've found that spot.

I know its obnoxious sometimes. It might a go away when everything sets in, but probably not. It might just move around the rpm scale depending on what changes you make to your car in the future.

I have an ancient exhust system. Its been there(the drone) at some point one way or another. With headers and without. I've been running the same mufflers and 2 1/2'' pipes since 97. California boss turbos by thrush..er AKA walkers. No X pipe here.

It changed when I went to a different rear gear, form 2.56 to 3.23. Its still there don't get me wrong but only a short time, as the trans is shifting much sooner. The power band is different now in the rpm range.

I should mention this too. I have an aftermarket sunroof in my Cutlass S. The obnoxious exhaust drone was all ways worse when it was open. Still is....

jread199

Yes they are x pipes, and who would of thought exhaust would be soo complicated. I tried to find this topic by searching the site, I guess i did not word it correctly. i built my first transmission which is a powerglide that i am currently using with an adapter plate, but i think I will install a 200 r 4 which I also have, thinking that will change the rpm at cruizing speed which hopefully will put the drone at a different speed hopefully one i do not sustain for a long time, thank you for the links and the replies.

oldcutlass

Probably be less expensive to just change mufflers.