Exhaust Studs... The neverending saga

[Timmayy]

Ok, so I traced a pesky oil leak on the exhaust side of the head to the 2 upper manifold bolts, which are tapped straight into an oil passage.

When removing the manifold, 3 of the 5 studs came out of the head quite easily on their own, and since I was replacing the long one at the back with a shorter one, at the suggestion of the local FIAT mechanic, I decided to replace all of the studs.

Easy-peasy, right? Well, not so fast...

I have now bought studs from 2 different sources and in both cases the root of the studs (the end that screws into the casting) are 8-9mm long which is about half the length of the factory studs.

My question is simply; Has anyone else used these studs in their engines? I don't expect the manifold to fall off or anything, but I'm just a bit leery using such a short root in an aluminum casting.

I could clean up the old ones, of course, but they are pretty rusty and I figured it was a no brainer too replace them. I've looked at ARP, and they have some nice M8 studs that look good in their catalog, but I'm having a hard time spending ~100 bucks on studs.

Any other suggestions or guidance would be appreciated.

-Tim

[ventura ace]

Tim,
What are the dimensions of the stud that you are replacing? (Total length, threaded length of short end, threaded length of long end). I'll check to see if I have any equivalent in my things.

Alvon

[Timmayy]

Thanks for the offer Alvon, but I have a local FIAT guy that I can get more studs from if necessary.

I did some more googling and found that the recommended minimum thread engagement for bolts over 5mm is 1D, so in the case of these M8 studs that would be 8mm, which is what they have.

I used blue Locktite on the lower studs and hi-temp silicone on the 2 uppers. They all felt nicely snug as I installed them, so I think I'm set.