Exhaust bolt choices

Doesn't matter on the studs, I've always used what they have in the Dorman drawers. What DOES make a difference is getting copper lock nuts, if you ever expect to take the thing apart again. I like the sort that has three round punch marks on the centers of the nut faces, not the ones deformed into an egg-shaped hole. I've always used antisieze as well, but I left it off one time on the VW and was still able to remove the headers with no problems. Have never run across the assembly you've described, has always been threaded studs into the manifold on anything I've had. They make a C-clamp gizmo for repairing busted studs, just clamps the exhaust flange to the manifold and is supposed to be permanent, or at least permanent enough to get the thing to a used car lot. Looked healthy enough to put some miles on, though.

With the change in fuel, stuff isn't rotting out as fast as it used to, less sulfur, no bromine from leaded gas, less acid settling into the joints. So getting stuff apart isn't as big a deal as it used to be. I've put 150K on the beast without changing out the exhaust Y at the engine. Three mufflers later, it's still solid.

Stan

If you are talking exhast flanges, not the manifold, you can use stainless bolts, but NOT with stainless nuts. They jam up and nothing short of a torch will get them off. Use brass exhaust nuts on stainless bolts or studs - or just use normal bolts and nuts and count on likely having to cut or break them off next time.

On exhaust studs, use brass exhaust nuts whenever possible - makes the dissassembly job a lot easier next time.

As for the lasting longer - all those points are valid PLUS the factory USUALLY uses stainless steel ahead of the converters because they have to warrantee them for 100,000. Many cars are now stanless manifold to tip.

On the junction of the exhaust manifold and the pipe, this van had hex head cap screws not studs. I was going to use the same thing to replace them.

The fastener that broke was some sort of carriage bolt or perhaps something like a wheel stud with a flat head on one side and the other side was threaded to hold a nut. These appear to be tack welded to the flange so I am going to hit them with the grinder to cut through the weld and then try to use a C-clamp to press them out.

So it sounds like the recomendation is for a stainless bolt and brass nut to replace the carriage bolts on the flange, But for the cap screws holding the pipe to the manifold should that be stainless or what? These cap screws thread into the exhaust manifold. My goal here is the next guy will be able to remove them in one piece.

Roger Shoaf

But for the cap

I would replace the cap screws with studs and brass nuts.

Dan

Some of the stainless screws I've bought in hardware stores turned out to be weaker than Grade 2. The flange bolts here were turned from 303 rod stock:

are for ball joint flanges on a stainless exhaust where road salt destroyed the original welded-on bolts. I should have used TIG instead of 308 stick to weld them.

Personally I buy exhaust bolts and nuts that will get hot from the dealer or at least the Dorman rack at Pep Boys, hoping they used appropriate steel. Diesel glow-plug antiseize allowed them to unscrew even after the hex nut had corroded to a cone.

jsw