Built89

I've got a '89 with a 3.0 V6. Just had the Downey headers installed and full new 2.5" exhaust all the way back.

It seems that between 2800-4000 rpm there is a horrible metallic noise, but also usually only under somewhat hard acceleration, a vibration rings out of (what seems to be) the right side header. What in the hell could be causing this?

Bolts are all checked and tight, no leaks can be found. I did notice that 2 of the pipes are touching prior to the collector but am not sure if this could cause the very loud noise/rattle.

Also could the minimal clearance between the starter and the header be the issue? Like as the engine torques could the headers actually be hitting the starter?

Any input very much appreciated. Thanks.

mr toytech

are the collectors welded or clamped? and no the header cannot flex and hit the starter but make sure you heat wrap the starter so it dont cook it.

mr toytech

if they are clamped try tightening the clamps. mine work loose all the time. thinking about welding them.

MAXIMUS1968

Ive changed gaskets on mine 3 times cant find any leaks, but it sounds like that to me on mine as well during acceleration...i finally have gave up

Built89

Its welded, the headers were trimmed a bit and a bend was welded on and then to a flex joint. But everything's welded.

Damn, you get this noise too? Given up? Say it ain't so!

stormin94

I have a very similar setup, and I get a noise also. Like a vibration kind of. I think it's the exhaust hangers. Or, the first muffler shop that I went to in Sacramento welded up a "Y" pipe to connect the headers to the single 2.5" exhaust, and he fabbed up a "T" shaped pipe instead.

Built89

Hmm...well my "Y" pipe is a little more "T" shaped as well. Interesting. Do you think that could be causing the vibration?

I also noticed that there are no exhaust hangers on that side of the vehicle, (since there was no exhaust there previously). Could that be a culprit?

stormin94

I think maybe. The way that I checked was with one person revving the vehicle, and me looking around at the exhaust to pinpoint the noise.

Built89

I'll have to try that, although I've revved it alone and the vibration doesn't seem to be present when the vehicle is stopped. Weird weird weird....

stormin94

Found out possible leaky header gasket. Not the end of the world, but kinda annoying....

Elvota

A revved engine generally won't twist very much as there is no real torque. Make sure your clearances around the header and exhaust to the frame or other components is good.

Maybe two parts are coming in contact under hard torque? Looks for signs of wear on the headers or exhaust indicating such.

Built89

Ok so after some months of horrible noises coming from my exhaust the problem has been found!

Prior to installing the Downey's I was running 2.5" straight through exhaust to a flowmaster 50, no cat. It sounded deep but fairly quiet and predictable.

Well it seems that the Downey's opened up the exhaust just a little too much, as air was being sucked back in the tailpipe on deceleration and the whole exhaust would scream and shake as it did this! I replaced my old exhaust system with the same but new setup with a fabbed x-over behind my t-case as the old was nearly dead.

I also lost about 4miles per gallon after original install.

A resonator has fixed my problem and the truck sounds nearly stock in the cab now. Woohoo!

904_runner

So putting on headers make you lose 4mpg? WHAT?

Built89

Sure did, perhaps due to the lack of backpressure? I also lost low end torque initially but it has since returned with the resonator.

Jay351

That about sums up my suspicions - 2.5" is just too much pipe for a 3.0

Elvota

What brand resonator did you go with?

In what order is your setup? Example: cat, resonator, muffler.

Built89

Not sure of the brand, about 14" long is all I know. No cat, (i know i know...) and then a flowmaster 50.