Way off topic question?

Before ya’ll beat me up for having a GM engine, it’s what came in the boat. And as much as I would like to change that the cost would be too prohibitive. I’m sure there are some on here who know about GM engines.

The engine is Volvo Penta 5.7 (GM 350) with the Vortec heads with the center bolt valve covers. The intake manifold is the 8 bolt design with the center 4 bolts missing. I have yet to pull the intake, but what are the odds the center 4 bosses are there in the heads? Would GM cast two different heads one for an 8 bolt intake and another for the standard 12 bolt intake?

If they are not there would it be acceptable to just pipe plug the center 4 in the intake manifold?

I think maybe I found the answer to my question. After looking at hundreds of photos of the heads, it appears they would not need a second casting. It looks like just a matter of drilling and tapping the holes. Some heads I saw had the holes drilled and tapped and some didn't, lol!

Doug Rahn wrote:I think maybe I found the answer to my question. After looking at hundreds of photos of the heads, it appears they would not need a second casting. It looks like just a matter of drilling and tapping the holes. Some heads I saw had the holes drilled and tapped and some didn't, lol!

AND, different years have those center bolt holes on a different angles.

rmcomprandy wrote:

Doug Rahn wrote:I think maybe I found the answer to my question. After looking at hundreds of photos of the heads, it appears they would not need a second casting. It looks like just a matter of drilling and tapping the holes. Some heads I saw had the holes drilled and tapped and some didn't, lol!

AND, different years have those center bolt holes on a different angles.

I came across that too Randy.

The Small-block Chevy cylinder head is designed for 1987-95 Throttle Body Injected (T.B.I.) and Tuned Port Injected (T.P.I.) 5.7L S/B Chevy engines originally equipped with centerbolt valve covers. The intake bolt pattern utilizes the 1987-95, 73° angle on the two center bolts.

The Corvette centerbolt cylinder head is designed for 1986-91 Tuned Port Injected (T.P.I) 5.7L small-block Chevy Corvette engines originally equipped with centerbolt valve covers.The intake bolt pattern utilizes the 1986-91 (straight) 90° angle on all bolts.