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Old 03-24-2010, 03:25 PM   #1
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Default WHY the hell is my exhaust manifold leaking?????

Ok here's the bullshit story, I keep getting leaks at the exhaust manifold-to-engine connection.

Initially when we welded the manifold together it was a bit warped, so instead of resurfacing I just used this thick/weak gasket material **** that held up for all of 2 months. Started leaking, so I took off the header, half *** resurfaced it (with a belt sander which didn't work out good) and reinstalled with a pressed metal gasket. That worked for all of 2 weeks before started majorly leaking.
So I take it off 2 weeks ago, have it resurfaced CORRECTLY and flawlessly, and reinstall with same pressed metal gasket (good one).

The increase in power/spool was HUUUUUGE. I almost shat myself. Very happy with it.

Then just last week it starts leaking again after I did 6 back-to-back pulls from 40-110.

It was leaking but still somewhat ok. Then 3 days ago I did a couple pulls through all of 4th-5th. so 60-110ish roughly.

NOW ITS LEAKING LIKE A BIIIIIIIIIIIIIIITCH


The manifold is a custom tubular using thick *** stainless steel weld els, and the flanges are from weirtech. Nothing shitty or messed up.



SO WHAT AM I DOING WRONG!!????????

Don't want to fix it just to have it happen again. Someone please advise: am I overtorquing the bolts? Am I heating it up too much by doing back to back pulls for about 5-6seconds at a time? What?
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Old 03-24-2010, 03:41 PM   #2
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Sounds like the way you assembled it resulted in making a spring that contracts when heated. Do you have relief cuts between the runners? Might try that (and then resurfacing again).
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Old 03-24-2010, 04:09 PM   #3
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is it bowing? or cracking? s/s is a pain in the **** to work with, it warps cracks easy & expands at different rates to alloy... get it made out of steam pipe & never worry about it again

p.s how much power u making now?
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Old 03-24-2010, 04:14 PM   #4
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Quote:
Originally Posted by 18psi View Post

Don't want to fix it just to have it happen again. Someone please advise: am I overtorquing the bolts? Am I heating it up too much by doing back to back pulls for about 5-6seconds at a time? What?

This should not be the issue, when on track we are doing back to back to back to back pulls for 20 min straight, and i am yet to warp my absurdflow setup.

The absurdflow setup does not have relief cuts on the flange either.
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Old 03-24-2010, 04:43 PM   #5
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Too much carbon and not enough graphite in the mix...well possibly. There are many different grades of cast iron, just read through the racing brake site. My ABSURDflow manifold warped once, then I surfaced it and its been fine since.
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Old 03-24-2010, 04:55 PM   #6
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I think its bowing, but not sure. I'll pull it tonite and post up complete results.

Are you guys torquing them to certain spec?
I don't have relief cuts in the flange, but then many manifolds don't and they hold up just fine. Is it just a coincidence and I'm just trippin? I'm running rich as hell to stay safe (lowest being mid 11's so its not like its washing out cylinders or anything) with super conservative timing (highest 10* in boost and 30* out of boost)
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Old 03-24-2010, 04:58 PM   #7
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Quote:
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Are you guys torquing them to certain spec?
I don't have relief cuts in the flange, but then many manifolds don't and they hold up just fine. Is it just a coincidence and I'm just trippin? I'm running rich as hell to stay safe (lowest being mid 11's so its not like its washing out cylinders or anything) with super conservative timing (highest 10* in boost and 30* out of boost)
Mine are all just hand tight, which is pretty much as tight as i can get them with a wrench without stripping them.

Your timing is low, im about 20-25 @ 14 psi
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Old 03-24-2010, 05:00 PM   #8
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I'm at about 12-13 now and will most likely start raising timing soon since I have det cans now.

No Idea no power, but it pulls very strong, I'm guessing 250whp
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Old 03-24-2010, 05:34 PM   #9
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Quote:
Originally Posted by 18psi View Post
I'm at about 12-13 now and will most likely start raising timing soon since I have det cans now.

No Idea no power, but it pulls very strong, I'm guessing 250whp
I saw the build thread, where is it leaking? pics?
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Old 03-24-2010, 05:45 PM   #10
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Its not a tune problem so don't worry about fuel or spark. Its a metalurgy issue.
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Old 03-24-2010, 05:49 PM   #11
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Resurface it again, tighten it from the middle outside, use an OEM gasket. If it happens again you can try relief cuts.

Interesting note, when my flange was warped a bunch of the nuts came loose. I skimmed it and magically they all stay tight now.
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Old 03-24-2010, 07:52 PM   #12
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Ok. will do. Thanx guys
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Old 03-24-2010, 07:58 PM   #13
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Quote:
Originally Posted by Savington View Post
Interesting note, when my flange was warped a bunch of the nuts came loose. I skimmed it and magically they all stay tight now.

They didn't want to fail you again and feel your wraith. that's the way to do it!
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Old 03-24-2010, 08:01 PM   #14
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Also advance your timing. I drove my car for 3 days with static 10* timing, and my turbine housing/downpipe flange magically went to ****. Not fun taking it to exhaust shop and paying them to weld on car.

This will heat up your hot side parts more than necessary.

If you're still having problems you may consider that you might have warped the head side of the flange if you drove around long enough with a leak. The way the head is setup it's doubtful, but I'd hate to see you chasing your *** forever.
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Old 03-24-2010, 09:02 PM   #15
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same here. I'm going to fix it permanently this time
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Old 03-24-2010, 09:23 PM   #16
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*cough* I have a fix for ya... It has twice the cylinders. Thank god none of my cars have ever had exhaust leak issues, outside of rusted through pipes. Just another story to further reinforce my feeling of Miatas and BP's.
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Old 03-24-2010, 09:31 PM   #17
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its still worth it. the car hauls *** and sounds great doing it, and that makes it all worthwhile
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Old 03-24-2010, 11:23 PM   #18
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I guess I'm just not willing to spend money like I used to be. I've had too many cars that I've spent way too much time and money on, and not enough driving and enjoying. Which is why I want something fast and decently reliable, which I hope I can do with a LS1 in near stock form. Any car has problems, but it seems like I have seen more Miata horror stories and troubles than any other car I have dealt with. If it's worth it to you, that's what matters. I guess a flange isn't a big deal though, I just can't stand those little problems. The ones that seem to keep coming back.
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Old 03-24-2010, 11:50 PM   #19
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So the leak is from cyl#4...

not the middle..


WTF
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Old 03-25-2010, 12:09 AM   #20
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Quote:
Originally Posted by 18psi View Post
So the leak is from cyl#4...

not the middle..


WTF
Isn't your DP DIY? How tight is it to install to the turbo? Does it put any pressure towards the front of the car? Doubt that would ever be enough pressure to put any kind of real strain on the manifold/head flange. Would probably cause a problem at the turbo long before it would at the head. Just a thought. How did you tighten the nuts last time? Like, what pattern if any did you follow? Might just be the way it was tightened.
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