Joepoppa1

I've dug around the forum and wasn't able to find any threads about this so here it goes. Recently installed a header on the car. I was worried about the flanges not being flush or being warped as it was one of the less expensive units. I filed them down flush, no warping, but the thing keeps blowing out the gasket to the cat. I've replaced 4 so far, and they last about a week or about 100 miles. It has the stock mounting flange on the cat, and like I said the flange on the header is true. is there anyone out there who can help shine some light on what to do with this? I thought it might have something to to do with a clogged cat as I was hearing a rattle and the CEL came on with "low efficiency" error showing. I looked at the cat and it was clogged, so I knocked em both out thinking the backpressure was too much.. (Ran like a scalded ape after that!) But the issue returned. Welding skills are decent, and have access to someone who can weld their butt off, so mods are not out of the question. I'm wondering if the mismatch in the diameter of the collector and the diameter of the cat. inlet is causing some buffeting that is chewing it up, or if the gasket is just that crappy. I'm using the felpro gasket from Autozone. It appears to be just a metal screen sandwiching some material. I wonder if I need a stock one with the metal donut in the middle.. I want to pick some brains before I go and drop $15 on something that will do the same as the $5 gasket. Thanks for your help.

Oldblue

The gasket that came with the header is the one blowing out?
And the Felpro gasket?
If they are the flat three bolt hole gaskets and the original is a donut type mesh ring , then spend the extra 10.00 but if they all are the same design the it's the header flange that is not keeping sealed to the down pipe flange, are they both true?

donbrew

If the two pipes are different sizes then the stock gasket size will not work. One with a ring won't do anything if it does not match the holes.

There is very little extra. Material on the gaskets.

Joepoppa1

yes, both the felpro and the gaske that came with the header are blowing out. the flanges are the same size and Ive made sure they are flush. but Im wondering if it warps when it gets to operating temp. the inside diameter is a bit bigger on the collector of the header than the opening of the cat. I havent tried the stock style with the metal ring in the middle... I have a pic here that shows the difference between the stock manifold and the header. It keeps blowing out the bottom of the gasket. Im pretty sure that they are true. I filed them down, spraying guide coats to make sure they were flush. the only way to really make sure is to take them to a machine shop, but like i said. it may warp a bit when they heat up. wondering if I should file it when its hot...

donbrew

Well! the new header has an oval hole, the old downpipe has a round hole. Do you think a gasket with a round hole would work? Did you put the gasket up against BOTH pieces for fit?

I would try one of the "generic" gaskets that are much larger than the flanges, but fit the bolt holes and the center hole.

The other possibility is that the bolts/nuts are not fully engaging and pulling the parts tight. I had that problem with an after market downpipe that had a thinner flange plate; they could not be tightened any further, but they were not tight enough. Washers fixed it.

Joepoppa1

Im skeptical that the stock one will fit right. I think it will blow out past the metal ring.. Ive cranked down the bolts pretty tight, and they have tons of thread left. It wont hurt to try some washers. I can get this gasket replaced under warranty and drop the $1 for the washers LOL

This is the gasket I have on it now... this next one will be #4.

Duralast By Felpro/Exhaust Flange Gasket 61362 at AutoZone.com

but I think Im gonna go with this instead

http://www.gmpartsdirect.com/part_images/15235773.jpg

Snoopy

You could also get a sheet of GOOD gasket material and do as we did in the old days.........cut it with a ballpeen hammer.

Joepoppa1

Thought about that too, but not sure where to get that at though.

donbrew

I know that NAPA has it.

Those stock gaskets will not fit the header, I can see that from here. The hole in the header is oval, there is not enough metal around it for the two pipes to seal on the gasket. One with a ring won't help because it needs contact on both sides.

DrLoch

I have had this problem in the past, not with an HHR/2.2 but with a big block. We would cut our own gasket and use high temp sensor safe RTV on both sides. With out race engines we didn't use gasket between the header and the head all we used was Hi Temp RTV. Granted those engines would only go 2 races before the were changed out but the Hi Temp did seal.