The Stovebolt Site Forums The Shop Area Engine Shop Big GMC V6 exhaust manifolds

I am working on a 68 GMC Tractor, I don't know what series it is because it has a 78 Chevy crew-cab pickup body on it, from the way it's built it is a BIG one...anyway, it has the 351E V6 engine that has the valve covers shaped like the 348/409 chevy v8 engine. The exhaust manifolds have a "flared bell-shape" where the header pipes connect...my friend had an exhaust shop put new dual exhaust on this but they didn't put the proper header pipe connector and what I have is a straight header that will push up into the manifold and of course fall right back out..Do any of you remember the 2 piece clamps that originally held these together and better yet, have you seen them for sale anywhere? I have called and researched to no avail...is it my imagination, or did those clamps exist? Does anyone have any ideas? I still can't believe that the muffler shop put these pipes into the cast manifolds, tacked-welded them, and expected them to stay anytime at all. I would like to find the header pipe flared connectors and clamps and fix this properly......LamarB

Do I have this right? The manifold has a taper to the inside,looking like the pipe would have to be the opposite of the bell shape that most GM's use? If this is what you have,there's a double beveled packing that fits into the manifold bell,and has the same shape on the muffler side,so the correct sized bell shaped flange would slide down on the pipe and attach to the manifold with either 2 or 3 bolts, compress the packing around the pipe,and squeeze the packing into the bell part of the manifold,making a tight seal. You should be able to get these packings in a variety of sizes and materials with different hardness,so they will be soft enough to compress but hard enough to last a while. If I misunderstood your design,never mind...
Speed

Hi Speed, thanks for the input....but these manifolds have the bell shape on the outside, there are no ears with either holes for bolts or studs, and the header pipes are straight...after some research I'm beginning to believe that the header pipe should be shaped the same as the manifold with a sleeve inside to hold an exhaust donut, then a two part clamp holds the two bell shaped ends together. I haven't found new header pipes or clamps so I am working on a design that would hold the pipes up into the manifold somehow......any ideas anybody.......lamarB

Lamar, ya might check around at our V6 guru Jolly\'s place , he's quite into the big GMC's aa well

Bill