Prevent Exhaust Studs From Snapping?

[Missileman]

My 80000K original 32 gtst had metal fatigue in number 1 and 6 but only broke when I removed the manifold, so I would be confident the new ones will last a similar time.

[GTRPSI]

Its pretty common to have them fail, most people just replace the studs on the head whenever the mainifold or head is off.

Many heat cycles makes them brittle, however all of the previously mentioned issues such as warped manifolds etc add to the issue.

[Missileman]

I will add, besides the studs replace the yokes, washers and nuts too, I had quite a few of the stainless conical washers that were cracked in half.

Also I was talking stock engine, so once you start winding in some boost, manifold and turbine temps go up and the heat expansion will be greater, so they may only last 40 000k

Another thing, when studs break in the alloy head, the part of the stud which comes away, nearly always takes the last one or two threads with it, don't panic there are plenty left, you'll junk the head before you need to worry about helicoils.

You will also be tempted to over tighten the nuts which is a bad idea, as it will stop the exhaust manifold from sliding over the washers and yokes and put more stress on the studs. I use a open end / ring spanner (the ring end has offset) to tighten them, the open end will just fit the 1/2 inch drive of a Tension wrench, so set the torque you require and feel with you hands how much force is required through the spanner to reach the setting, then try and replicate that exact force when tightening up the manifold, you will be surprised how little force is required.

Edited February 13, 2015 by Missileman

[iruvyouskyrine]

Nope not at all. Until you start hearing an exhaust leak you are in the clear.

I purchased my RB20 R32 and flogged the shit out of it for two years happily. When it came out for 25 conversion I found there was only 8 studs holding the exhaust manifold on, the rest were snapped