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Red_Chili
06-27-2009, 05:23 PM
So for the second time, I've started to blow out the gasket from a three bolt header collector flange union.

1) what is contributing to this? There is a flex joint just downstream of the union so I doubt mechanical stress is causing the failure.

2) what is the solution?

I thought about putting some kind of interior sleeve in the downpipe, so the exhaust would already be past the gasket before it could work against it. I dunno, seems kinda tedious for a maybe-solution.

TIMZTOY
06-27-2009, 07:12 PM
if you have a cloged cat it will be causing excessive back pressure in the exhaust side of the engine.. which will blow out the weakest link.. IE gasket
how offten is it blowing out ?
what motor ?
notice it more after taking long trips, short trips, exhaust hot, after high revs ?
how old is your cat ? most cats are reccomended to be replaced at 60,000 - 100,000 mile intervels..
you would or could also notice slightlly less power and throtle responce. depending on how bad it is cloged.. could also be cheap gaskets..
try OEM toyota gaskets i belive there around $13 ea

DaveInDenver
06-27-2009, 07:28 PM
FWIW, the gaskets that LC Engineering supplied with my header would blow out a lot, too. So I had a couple of things I tried or was going to try. BTW, the links are just quick search examples, not exactly what size or anything.

My first step (which worked) was to use copper collector gaskets. They crush and don't blow out, even with the mighty 22R-E hot rod. Oh, I also used jam nuts with split washers instead of just split washers and regular nuts, I suspect the bolts were getting loose with the thermal changes.

http://summitracing.com/parts/MRG-7177C/
http://static.summitracing.com/global/images/prod/large/mrg-7177c.jpg

The next thing I was going to try was Percy's carbon gaskets. Still gaskets, but tolerate much higher temps (2000F apparently), although I suspect they would not crush like copper.

http://summitracing.com/parts/PHP-68017/
http://static.summitracing.com/global/images/prod/large/php-66001.jpg

My final step would have been like you mention, sleeves. This would have been on the assumption that I have an alignment problem (which I do, the flanges don't line up all that well). These would take doughnuts instead of flange gaskets I think and some welding or fab I'd expect.

http://summitracing.com/parts/HED-21122/
http://static.summitracing.com/global/images/prod/large/hed-21122_w.jpg

Red_Chili
06-28-2009, 10:54 PM
Interesting approaches.

The cat is fairly new (less than 20K miles) on a custom 2.5" exhaust behind a 3.4L in an 87 SAS 4Runner. Pretty free breathing. The frequency seems to be no more than annually.

Art Volmer
06-29-2009, 08:53 AM
Bill I have seen this problem and it is usually poor gasket construction. The copper gaskets are probably your best start. Good Luck, Art

mtnrunner
06-29-2009, 09:44 AM
I ran the Copper Gaskets on my Taco with TRD headers. Until I did, I was blowing them out on the 3.4l every 6 months. Go with the Copper Ones.

rover67
06-29-2009, 10:32 AM
I've had the copper ones for a while now and they work fine. I've even reused them a few times which i know is a no-no..

Beater
06-29-2009, 11:14 AM
wanna have an exhaust party? I need to switch out the flex pipe and put these in..

j

Red_Chili
06-29-2009, 12:54 PM
Sure... although I am trying out some Mr. Gasket gaskets that On Track Performance recommended. Sounds like copper gaskets and the copper-colored hi temp RTV is the shiz though. C'mon by. Although that means you will have to sit around waiting for the exhaust to cool. I'm sure I could find SOMEthing you could help me with while doing that... :lmao:

Beater
06-29-2009, 01:46 PM
well, one should always work on exhaust warm, though not hot. I need to install my wrapped crossover. Are you still using the inner gasket as well as the outer gasket?
j

Red_Chili
06-29-2009, 02:04 PM
I ain't got no inner or outer gaskets... unless you are talking about the gaskets at the factory manifolds, which I've not touched.

Beater
06-29-2009, 03:49 PM
interesting, I had a inner ring gasket at the down pipe on mine.

Red_Chili
06-30-2009, 12:41 PM
Nothing on mine is factory, past the manifolds. Not even the crossover.

If I were to put in a 3.4 myself, I think I would disassemble and reassemble - backwards - the stock crossover including the downpipe connection. Toyota put a lot of thought into it (heat shield notwithstanding), and it would save bux deluxe.

TIMZTOY
06-30-2009, 04:22 PM
i diddo the better gaskets... cheap and easy way to eliminate other problem areas