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Posted by David Sherman [24.32.202.83] on Monday, March 29, 2010 at 00:24:43 :
In Reply to: m-37 manifolds posted by mike [4.225.149.26] on Sunday, March 28, 2010 at 15:18:59 :
If you have a torch and aren't too picky about how it look, it's not hard to repair even big holes by brazing. Much easier on the metal and less tricky than welding. I have brazed a couple and they held up fine. Any heat process will warp them, so you'll need to have the block surfaces ground by a machine shop. Because the intake and exhaust bolt to each other as well as to the block, the proper way to do it is to assemble the intake to the exhaust with the 4 long bolts and a gasket. I have made my own gaskets with exhaust gasket material cut with a roto-zip tool and doped them up with black furnace cement because the castings are rough and pitted. Whatever you do, first assemble the intake to exhaust loosely but with the final gasket and gasket dope in between them. Then temporarily bolt the assembly to the block and tighten it down reasonably snug, but don't over-do it to the point of bending or breaking anything. Then torque down the four bolts that hold the two manifolds to each other. Then unbolt the assembly from the block and take it to the machine shop and tell the machinist to grind them as one assembly and not to unbolt them. This sequence applies also if you are combining manifolds off of different engines even if you didn't heat them. Also, there are supposed to be special conical washers and nuts on the outer exhaust manifold studs. These clamp together and avoid loosening due to heat cycles. Unlike normal lock nuts, the pointy end of the nuts goes in towards the washers. Quite often they've been replaced with ordinary nuts and lock washers, which are likely to come loose. Similarly, the inner studs are supposed to have special very thick washers on them to span the gap between the two manifolds, but often someone has just used normal hardware-store washers that bend down in the middle and don't clamp the two parts equally. Nobody seems to have the special conical nuts and washers any more.
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