Five questions:

1) Is it ever OK to reuse an exhaust gasket?

2) If yes, what is the deciding factor?

3) Do exhaust gaskets "give" or "crush" into place when installing?

4) Should it be possible to run a 0.005" feeler gauge behind the gasket when it is torqued, but before heating it up?

5) Is high-temp silicone (as used on oxy sensors) a solution even worthy of consideration? (I've always set exhaust gaskets dry)


I'm pretty sure I know the answers to these... but I'm kind of desparate, & there are people here with far wider experience than I have.



Background: Final weekend before SevenStock, and I finally got my repaired exhaust headpipe back, only to realize I do not have a new manifold-to-headpipe gasket (thought i hada speare left), and the odds on gettting one on a Sunday, or within a couple days, are absolute zero. Odds are near-certain I'll have to order one.

So, taking a chance, I just finished bolting the pipe in with the old gasket, and I can slide a 0.005" feeler gauge between the gasket and the manifold on the side I can reach. Five thousanths is not a lot, but it's not air-tight, either.

I need to get the car completed and smogged by next Friday, or nearly three months of refurbishment work will have been... well, not exactly wasted, but I'll miss out on the driving goal behind it, which was to get the car to SevenStock this year.

And naturally, I have to work all week.

Advise/experience/ suggestions? Looking only for a good-quality solution, not something that will cause trouble later.

 

I can answer #5. No. No matter what rating silicone it is, it will not last more than a few seconds if its exposed to exhaust gases, ESPECIALLY from a rotary furnace. Copper sealant, while not as thick, can be useful if its just hairline leaks.

EDIT: I don't think a slight exhaust leak would cause you to fail emissions would it? Unless they automatically fail you, you would actually have less gasses coming out the end of the tailpipe theoretically, and it wouldn't effect the reading I wouldn't think? Also, is there an exemption rule out in CA for the age of the car? In Texas, if its 25 years or older it doesn't need to pass smog. Just take it to the most run-down place around, with the stupidest people working there, and assure them that it only requires a 'safety only' inspection and you might just be in luck. (this actually worked for me) Do you have another car? Rip that sticker off and put it on your 7, they'll never know.

 

California used to do a rolling age-related exemption, but dear Governor Ahnalt did away with it a couple years ago. The pathetic p-whipped bahstid. We have the most stringent smog standards in the country; vis and dyno 4-gas test, and the dynos even have cameras on them.

Problem turned out not to be the gasket; I found the new one I was hoarding.

Turns out the repaired headpipe is off to the right at the first junction by a little less than a degree. As the exhaust extends backward, though, that error is amplified (due to the rules of trig and projected angles). By the time it reaches the trans mount for the exhaust, the total error is about 5mm...and was just enough to prevent the headpipe from mating flat with the thermal reactor (or TR, also known as the exhaust manifold).

The first junction is critical that it be tight, because with the stock 80 exhaust, its a co-axial connection: exhaust tube down the middle is surrounded by a cooling chamber that is fed from the smog pump. if that cooling connection leaks, then the exhaust headpipe can overheat and fail. This is why my pipe needed repair; it had overheated so hot it literally melted the weld. But it apparently got welded just slightly out of alignment when it was repaired. I'd test -fitted it after it was tacked, and it fit fine; I can only guess that the tack-welds had just enough flex that the error warped out when torqued. Now that it's solid-welded, no flex.

I thought I could adjust out the repair error working backward: I made a couple spacers to let me move the trans exhaust hanger the necessary 5mm to the right. That let me perfectly mate the headpipe to the TR. No gaps.



But, it was just enough off of true that as the exhaust extends all the way backward, the angular error keeps accumulating. By the time I get to the junction between the back of the heat exchanger and the midpipe, the error is large enough that I can't mate the two; not enough give in the rubber exhaust hangers, and the back end of the midpipe comes in contact with the frame of the car.







Bottom line is, looks like I'm hosed in the short term. I have to get ahold of a good headpipe, and I can't afford the going commercial rate. There's just not enough play in the exhaust system design to let me use the repaired one, and there's no way to cut it apart and repair it again.

I'm bummed - - no chance I'll find one I can afford, and get it in, in time for SevenStock.

 

Just go and buy a small sheet of good quality exhaust gasket material, trace the old one and cut a new one (or 3). You'll have it done start to finish in a couple hours

EDIT: Remember to clean the mating surfaces, clean and lubricate the threads to minimise the chance of a broken bolt. This will also ensure the best clamping fit for a given bolt torque.

You can also use some hi temp silicone sealant as well. I made my own Header Gaskets for my 12a that gets used mostly on the track... Works a treat!

Yes the metal lined exhaust gasket material does have a crush feature.

 

id drive it to the muffler shop as is, they can prolly fix it

to answer the original questions

1. yes, its ok to reuse

2. you can reuse the gasket if its in good shape

3. the gaskets dont seem to crush much at all

4. ive never tried to put a feeler gauge in there

5. you can silicon the joints, it does work, ive even done it without the gasket at all and had it work.

 

Had a Eureka moment today while at work:

I have most of a stock midpipe, care of the (non-stock) welded exhaust system that '80's old school' gave me. It's missing maybe the front 3" and the flange ('cause it's welded to a cat I can't use) but I bet I can cut it free, weld on a new flange and a length of pipe, and set it to an angle to compensate for the error up front. I only need a few degrees of added twist at the flange.

The old pipe looks sound enough, & the rear flange is in fine shape; in fact, it's the only stock junction left on the whole system.

WOth a shot, and nothing lost but some time and a few bucks if it doesn't work.

To late for SevenStock, but that ship has sailed. Maybe SevenStock XII... heheh



It's not solution #1, but it just might get the job done. Provided I can find a matching flange... damn thing is THICK!

 

Just get new ones from Mazdatrix they are not expensive.

http://www.mazdatrix.com/e6.htm

 

Not horribly expensive... but I was working under a time limit, didn't have days to wait.

Issue's changed since then, anyway, and SevenStocks no longer possible.