I milled down an aluminum manifold quite a few years ago and it worked fine. I wouldnt take too much off though. Not sure where you would find a new one, last time I checked, they were unavailable.
Good practice (and not too much work) to remove the elbow, clean both surfaces and new gasket yearly or every two years minimum before the aluminum surface becomes too pitted to seal (and check the flappers while you are there). Certainly if you cannot buy a replacement.
@Dubed @Scott Danforth @Lou C , Thanks for the comments.
I have a cast iron manifold. I will try milling it, depending what happens next. The gasket with permatex are holding a 15 psi pressure test for now. I tried starting it yesterday, very briefly. It coughed, sputtered but no start. Pulled the plugs, all four were slightly wet with water. Coolant system is still holding 15psi very steadily, so I think it was just a bit of residual water after I'd blown it out of the cylinders by cranking and with compressed air. Will be trying again shortly.
Thanks for the tips on gaskets, Scott. For no particular reason, I didn't check NAPA here after three other suppliers didn't have rubber gasket material. There was no o-ring on on the bolts when I took the covers off, and I hadn't noticed leaking around the bolts, I reinstalled without o-rings, with permatex around the bolt hole as well as well as all of the exchange seating faces. I'll be getting the o-rings and gaskets for the next change. (Curious side note, I was surprised to find that the center of one end of the 3" heat exchanger (on my other engine, port side) was 5-10 thousandths proud of the outer edge; there was no pitting or irregularity in the surface, just a consistent slope up from the outer wall of the exchanger to the center. Hard to imagine it was designed that way, or how it could have become that way over time. Anyway, I put the end plate on and we'll see how it holds. I hadn't noticed leaks from that plate before removing them all.)
Lou, I didn't post the best photos of the elbows, and missed posting the newer one. The very thin-walled one is the old one. Here's the newer one (pretty corroded also) and the manifold, before and after filing. And the replacement(?) gasket in place of the plate and two gaskets.
The structure in front of the engines is the diesel tank, for the espar heater. I appreciate the thoughts on repowering. I haven't given it much thought yet, but 4.3's if they are reasonably supportable still (at least more so than the 470's, from what I understand) might be what I do. I like the thought of 400 HP
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I like the boat too. It's growing on me as I work on it. Speaking of which, I better get at it.
