Exhaust Stud Thread Size, etc?
 

Hello again,

I thought I was on the home straight with my engine rebuild, until I mounted my SSIs, and one of the exhaust studs decided to strip the thread from the head rather than tighten. I am suspicious that this was a previous botched repair, because the stud is different from the others.

Initial thought is to use a helicoil insert, but before I commit, I need to confirm the thread size and pitch. I think the portion of the stud that goes into the head is 8mm with a 1.25 thread pitch. Is this correct?

Thanks in advance
Mark

Yes. Good luck.

yes you are correct. It is M8 X 1.25 pitch. I had the same problem and i used a stud that had 2 differents sizes threads on both ends. It was a M10 in one end (the end that goes into the head ) and the other end was M8 and the pitches at both end are 1.25.
It worked great. It retapped the hole in head to a larger size M10 to accomodate the new stud.
Tell me what you think. I would try first to rethread the hole, thought, before i go with M10. I did it only at last resort.
truly, filou. My engine was 2.7 L 74.

Thanks for the confirmation.

Helicoil repair kit for 8mm x 1.25 kit arrived in post today. I will attempt the repair this weekend. I had considered a composite 10mm,8mm stud, but didn't know where to source such a thing. I suppose I could use a 10mm,10mm stud and drill the exhaust manifold, but then the barrel nut wouldn't fit. I will go with the helicoil and report back.

Mark