New to the forum. I'm in the process of replaceing my exhaust manifolds, and risers on my 1988 Bayliner 5.7 OMC engine. I puchased a set of new Barr brand manifolds and risers. I started by removing the paint from the risers mounting surfaces, then started on the exhaust manifolds, riser mounting surfaces,and noticed that they didnot compare to the old ones I took off. The old ones being replaced before by other owners, 1 was a GLM brand, the other a OMC brand. Any way the concern I have, is the surface on the new exhaust manifolds where the risers mate on the surface, on 1 exhaust manifold where the cooling section is next to the main rectangular exhaust port, coming up through the center next to the corner, next to the bolt mounting hole is closed off by casting with no gap at the surface, and goes down in the cooling section 1 1/4" to 1 1/2" solid. The other new exhaust manifold, is the same way only all 4 corners in that area are closed off? (see pictures #1 and #2.) The old manifolds(#3 picture) are open all the way around, the exhaust center port. My concern is the reason I'm replaceing these manifolds, because of rust and corrosive build up. Then the new ones already have blocked off cooling sections to begin with.
Also I'm wondering if in that section, with no gap, there might be hot spots where the heat from the exhaust does not have time to disipate. I have contacted the place I purchased the exhaust kit from, but they say they contacted Barr Mfg. and said there is no problem, and also asked their in store mechanic, and he said no problem.
If that is so , why does the old exhaust manifolds have no castings in that area. I think that Barr Mfg. needs to clean up their molds. I went with Barr Mfg. because USA made now I'm wondering.
Thanks for any help on this matter.