Exhaust manifold stainless bolts ?
 

Given all the problems with exhaust manifolds leaking and the bolts corroding, why do we not see stainless steel bolt kits ? I have personally had to drill out bolts to remove a manifold on two different occasions, and its a major pain in the azz- I always have to decide if its better to just remove the engine first.

No more helping a friend remove manifolds for me !! Anyhow, I sent a request in to ARP for a comment on this question- and I had previously asked a local stainless steel marine fastener reseller the same question- he thought it was sometime to do with different expansion characteristics and that the SS bolts would work loose quickly, but he was not certain. Any comments ?

Whenever I buy new manifolds from SMI - they come with stainless bolts. Now .. I have had to re-torque them after 25 or 50 hrs. I've heard, but never comfirmed, that the stainless will stretch sooner.

Anyone have a definate answer?

In looking at ARP's stainless bolts- they are rated at 170,000 lbs tensile strenght- IIRC this is even higher than a grade 8 bolt. But I have certainly run across stainless fasteners that seem soft.

I also use stainless bolts. Infact when I purchased new manifolds for my Ski Centurian last year, they came with SS bolts. BTW, I have never had a problem with them becoming loose. I do retighten after the first heat cycle.




Darrell.

I always use stainless.

Stainless comes in different grades too. I wouldn't expect a grade 5 Stainless to stretch any more than a regular grade 5 bolt

ss bolts
 

i thank that the boat builders do not use ss bolts because of cost.maybe job security too.

the soft ones are the import imposters....

that even get sold to the government

If anybody can point me to a set of good stainless bolts for BBC Gen V or VI manifolds, I would appreciate it. OR, if somebody can provide me with a regular set that I can use to cross match to ARP bolts, I would be much abliged. I am thinking about trying to put together a few SS sets for my friends.

Dogturd, look on mercruiserparts.com for your motors exhaust bolts. They usually have the length, dia, and TPI on the parts listing. Then look on ARP.com and match them up with part numbers and order. I like the 3/8" bolts with 12pt heads that fit a 3/8" socket. Easy to get the socket onto them in tight places. A little bit of non-copper anitseize on the threads and they will last forever.

BTW merc carb 500HPs came with socket head stainless bolts on the exhaust manifolds, some accessories and the intake. I have never had a problem with the factory SS or ARP SS bolts. Also, I have gradually replaced almost all the fasteners for the bell housing, bracket etc and never had a problem.

For exhaust, motor mounts, etc, I take the hardened steel bolts (Gr. 5, 8, etc) and parkerize them, then dry-film coat them. No rust, no seize- ever. Takes a little bit of work but so does drilling one out of a head.