Exhaust manifold question

[enjoyer]

O.k. I blew the HG. I had another motor sitting for similar occasion. After the swap i heard a blow throug the exhaust manifold. Ok, i took it off, the gasket was shot. Also, i compared the manifold from my old engine with the one on the new(used, but lets call it new) engine. My old one was in better shape. So, i used it with a new gasket and it still blows. I took it of again and started to measure things. Turned out that the old manifold is curved in the middle. You can put a ruller on it and it see saw's. The new one is just opposite. It dips in the middle. Ok, you can machine one or another, but the question is this. if the two manifolds differ that much are the heads also curved inwords or outwords, because you can't swap manifolds from them? Is that possible?

 

[Reiketsukan]

It seems to my like you somehow got your hands on two warped exhaust manifolds. That mating surface should be flat. Can you get your hands on another exhaust manifold? Or maybe you could have a machine shop mill one of the manifold's mating surfaces to make it flat again? I'm not sure if that would be a good move with a 20+ year old cast iron manifold or not.

 

[radiod]

Yeah, you're options are pretty much machining or a new manifold.

Just a thought...if you've got it all apart, you might want to consider doing the manifold stud upgrade. It's common for the studs to strip out of the head, so Driftmotion put together a helicoil + larger diameter studs to help prevent this from happening.

Here's the kit mentioned:
http://store.driftmotion.com/static/i-716exhauststudkit.php

 

[enjoyer]

It seems to my like you somehow got your hands on two warped exhaust manifolds. That mating surface should be flat. Can you get your hands on another exhaust manifold? Or maybe you could have a machine shop mill one of the manifold's mating surfaces to make it flat again? I'm not sure if that would be a good move with a 20+ year old cast iron manifold or not.

On my old engine, i replaced the exhaust manifold gasket about a year ago and it was fine. No blow what so ever. Even now, when i took of that manifold, the gasket was fine. That's what's weird. How can the manifold fit on one engine and be useles on the identical other one?

 

[mkiiichip]

All of the surfaces need to be inspected for flatness.
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=49

 

[bwest]

And if you're going to have either manifold machined, check the runners and turbo mounting flange (near the divider) for cracks. I went through 4-5 manifolds just trying to find one that wasn't cracked.

 

[enjoyer]

And if you're going to have either manifold machined, check the runners and turbo mounting flange (near the divider) for cracks. I went through 4-5 manifolds just trying to find one that wasn't cracked.

Yeah, i know that. Two out of my three manifolds has cracks on the turbo mounting flange. Well, they became pretty much useless.