Bolt instead of a stud?

[boatgrunt]

I converted the exhaust manifolds on my 89 OMC 4.3 to a set of Mercruiser exhaust manifolds. The old studs were too short for the new manifolds, and I can't find studs that are long enough and that have the same pattern (both ends are different). Can I use bolts to attach the exhaust manifold to the block instead of studs?<br /><br />Thanks

 

[Lou C]

Re: Bolt instead of a stud?

Why not use whatever Merc used on their engines? Probably bolts, I think OMC was the only one to use studs. Nice thing about the studs is that you can get penetrating oil on the threads more easily to get the nuts off.

 

[boatgrunt]

Re: Bolt instead of a stud?

Thanks Lou C. The mercruiser manifolds that I am using are similar to the ones shown by tashasdaddy in the following post (see pic):<br /><br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=015105 <br /><br />Don S - do you know if Merc used a bolt for attaching approx 89 4.3 V6 exhaust manifolds? <br /><br />Thanks

 

[Haut Medoc]

Re: Bolt instead of a stud?

You can use bolts..... However, ....I would use an anti-seize compound on them, for future removal ..... JK

 

[tashasdaddy]

Re: Bolt instead of a stud?

i hope you are using 4"riser/elbow if you are not read all my posts and see the trouble i having. i had batwings. not enough room for 4" riser, 3" dumped water back down manifold throat.

 

[boatgrunt]

Re: Bolt instead of a stud?

tashasdaddy - pretty sure that I have the 3 " riser. Do you think that I will run into the same problem? What engine are you running? I am running a 89 OMC 4.3 V6.

 

[tashasdaddy]

Re: Bolt instead of a stud?

97 4.3 V6 it had the one piece manifold. tried the 4" riser and didn't have enough room to get to the Y pipe. tried the 3" like the ones in the aforementioned post, they poured water back dodwn the throat. i've got a guy consulting with mercruiser to come up with the correct solution. it worked before and i'm not changing my Y pipe.

 

[Lou C]

Re: Bolt instead of a stud?

89 OMC is not a Vortec engine,which could make a difference. I know that OMC changed from the batwing one piece to a two piece in 91 or so. Why not check out what they used, it was also used on the Volvo joint venture models too. I was thinking of using the OMC/Volvo parts for the two piece if I can't get the batwings in the future. Never had a water ingestion problem with the batwings so far.

 

[Scaaty]

Re: Bolt instead of a stud?

Back to the question (why do we always get off subject?) As long as you can get the studs out, bolts will work fine. Torque to spec, and again after a good warm up. You can also Google ARP, and they make any bolt or stud you would need. And use Grade 5 bolts (three raised equal spaced straight marks on the head). No less, no more. And I NEVER reuse old bolts for this application

 

[boatgrunt]

Re: Bolt instead of a stud?

Thanks Scatty. I'll get the Grade 5 bolts. Does Lows sell them? <br /><br />Lou C - I converted from the OMC batwings to the two-piece Mercruiser manifolds. To your point, maybe if I can determine what OMC subsequently used for a riser when it went away from the batwing to the two-piece, it could guide me in the suitablity of my current set-up.

 

[Lou C]

Re: Bolt instead of a stud?

Look over at www.dougrussell.com and look in the Volvo/OMC section, they have all the parts diagrams there.