As everyone who ever removed a manifold from a slant 6 knows, the two bolts that hold the manifolds together always corrode and break more often than not. Drilling the old bolts out is a real pain, and I'd like to prevent the situation for the next time I remove my Super Six setup.

I'm considering drilling the exhaust manifold holes out to a larger size and using a thru-bolt and nut setup. Does anyone see any downside to this fix? What about using brass nuts on all the manifold to head studs?

lancer_41@excite.com

I always use new brass nuts on exhaust studs, V8 or sl/6. Have you tried using MOS2(molt di-sulfide) type anti-seize lubricants on the threads of the bolts. It's a little messy, but it seems to work.
Another trick I've come across, is Mopar brand Heater Control Solvent/ Penetrating Oil . It's kind of a bubbly, blackish-grey penetrating solvent, that you use like spray WD40, only it's far superior to WD40. It actually dissolves some rust. Be careful not to get it in your eyes, it's pretty raucous. For really stubborn threads, I use a torch to heat up the threads, then spray it liberally with the solvent. It may take a few tries, just take it slow and easy.
I don't know how practical thru drilling would be. If it could be done, you might have to spot-face the seating surface for the nut, so it's square and flat and enough clearance for the (socket)wrench.


fglmopar@aol.com

Yes, I've done the anti-sieze thing before, but as you say, it's messy and I've found that the effective life span is not much longer than a bare bolt. It's great if you're racing and tear down periodically, but after a year or two, they begin to stick again.

One of the bolts was already broken on the manifolds I just dis-assembled, and the other broke despite several days of soaking in PB Blaster, heating with a torch and being especially careful.

Glad to hear the brass nuts work on a slant also. I've used them on V8's without any problems, but haven't tried them on the long manifolds.



lancer_41@excite.com

You could clean out the holes and then use long studs in the exhaust manifold. I have seen this on some later engines.

Chuck


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