Reconstructed totally wasted exhaust adapter for Palmer 392 engine iH

Album link showing the process I took.
https://goo.gl/photos/9enZHLqh9tCwRjDe7

From this


to this


Doing it myself saved more than half the cost. Finding 2.5 inch pipe cheap is not easy.
Hampton Rubber had a 6 inch pipe nipple for $12 and the square key stock of one foot for $3.

Years ago, I had a machine shop make 2 of these from steel for $75 each.
My engines use four of these.
I started engine and heard a loud noise. Not much except rust holding this together. Whacking with hammer showed how thin the cast iron had become.

2.5 inch diameter steel pipe joined to cast iron flange.
Hub end formed from 5/16 square key stock.
Brazed with silicon bronze rod inside and outside.
Bimetal hole 3 inch cut the flange to inset the pipe to provide greater surface area for brazing.

I used Permatex gasket maker high temp rated to 700*F for the gasketing, and also skim coated inside of the exhaust surface. I found it holds up protecting the metal from rusting.

This repaired piece is thicker than OEM and with the silicon bronze brazed surface, will outlast me.
If exhaust makers bronze coated their iron, then these parts would never rust away.

 

Put part to the test Sunday, went for 15 mile boat trip, worked fine.

I have been impressed with the Permatex gasket makers ability to seal and survive exhaust temperatures. The flange side must seal exhaust and keep coolant water in the end of the log manifold.
Formerly they used a physical gasket cut from some type high temp material, but I found over many years, those gaskets allow metal surfaces to rust along with bolts and bolt holes. Which makes them either break or be hard to remove.
So those gaskets must leak a little.
Using SS bolts and the Permatex keeps the bolts dry and no corrosion. I also make sure the mating surfaces are smooth and flat.
Flat here is what is important, roughness is ok, the gasket maker can handle roughness, you dont want parts joined to be rocking due to the surface having a contour.