Cut a warped JGS Manifold?
 

Hi all,

My JGS manifold has warped a second time after having it machined flat after the first episode. I am thinking about cutting it in the way recommended for the Greddy, between cylinder 1 and 2 and between 3 and 4. I also had a crack which I welded between 2 and 3 on the horizontal pipe before the machining. The weld is holding for now.

The warp is such that it has pulled away from the cylinder head at 1 and 4; convex towards the head.

Recommendations? I will try one more fix before scrapping the part.

Thanks,
Barry

buy a new one, my old jgs was like that too.

I had a JGS manifold that eventually cracked and warped due to my hard mounted DP. I had it resurfaced and rewelded and made relief cuts. The next time it warped I literally have to cut it off at the runners as it warped in such a fashion that I couldn't remove it from the studs. The problem was probably that I cut between 1&2, 2&3, and 3&4. Everything probably could have been prevented if I didn't bolt my DP to the tranny like I did, basically adding a lot of stress as it was to prevent the DP to hit my subframe, it also rendered the flex joint useless as it was after the mount. Moral of the story, stress is bad.

http://www.boostedmiata.com/cracked_...ld/cracked.jpg

http://www.boostedmiata.com/cracked_...brokeassdp.jpg

http://www.boostedmiata.com/cracked_...Small%2529.jpg

http://www.boostedmiata.com/cracked_...Small%2529.jpg

Thanks all for the info. My crack and warp look just like the above pictures. I had the downpipe bolted to the trans for a while, I guess that was a mistake.

Would it be worth resurfacing one more time? I will not attach the downpipe to the trans. Should I put in relief cuts or not?

If I replace it I may get the ETD shorty. It looks like the turbo position will be very similar to the JGS so that my intake pipes and downpipe may fit. Has anyone tried this manifold switch?

Thanks,
Barry

Do the JGS manifolds have oversized holes in the head flange? The holes near the ends (outside cyls 1 & 4) should be larger in diameter than the ones by 2 &3, and the center stud hole should be stock-size to account for thermal expansion.

My recollection is that they are all the same size, but I'm not certain.

Barry