Re: Advice on Studs for Exhaust Manifold ? 4 Questions . . . - Saab 9-5 Bulletin Board - Saabnet.com
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My indie actually used BOLTS to secure the exhaust manifold to the head. Not sure why. Consequently the heat shield is only held in place by a single nut at the front. The spring steel clips that affix to the failure prone long studs have nothing to affix to. It doesn't seem to be a big deal. To your point, using the short studs throughout should not be a problem.
I did notice the car making exhaust noise the other day and found the exhaust manifold bolts at the upper locations at cylinders 1 and 4 were only lightly hand tight. I had to tighten them. Not sure what the torque spec is. Blue loctite may have made this moot. Keep in mind that thread sealant like loctite loses effectiveness with elevated (>300F) temperature.
All this begs engineering questions as to root cause of stud breakage. Is it due to differing coefficients of thermal expansion and possible low cycle fatigue loading? We have an aluminum head, cast iron (assuming OEM) header, and CRES studs. Is CRES really the right alloy or are their better choices?
'04 Aero Sport Kombi
'03 Aero 5Spd, Krona, 290 bhp
'03 Linear 5 spd. Krona Mods, 350 bhp
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