The Pontiac OHC Six

[Scott Liggett]

One noticeable difference is the lack of side access plates on the block. I'm surprised they went that far in converting this to OHC. It shows the engineers were starting from scratch at that point. I'd like to see a 250 Chevy and this engine side by side and just do some studying.

Randal, are you interested in going up to the 215 hp cam, intake and such to start your efi turbo setup?

[67pete300]

[67pete300]

PS: somebody mentioned a turbo...if the manifolds in fact interchange with the Chevy 230/250/292 I know of a guy who makes a turbo manifold.

[TheSilverBuick]

Thanks for the pictures Pete. I had a curiousity about the motor mounts on the Chevy I6, I heard they mounted up different, and yeah they sure do.

Turbo exhaust manifold?

[TheSilverBuick]

One noticeable difference is the lack of side access plates on the block. I'm surprised they went that far in converting this to OHC. It shows the engineers were starting from scratch at that point. I'd like to see a 250 Chevy and this engine side by side and just do some studying.

Randal, are you interested in going up to the 215 hp cam, intake and such to start your efi turbo setup?

They eliminated the side covers and iirc right the block has a deeper skirt around the mains than the Chevy 230/250 too.

I'm not sure what I'm doing for cam's just yet. I'm not sure getting the 215Hp cam is the right track yet, particularly when I'm running lower compression than the 215Hp set up. Pontiac used the same pistons in the high compression engines and the low compression engines, different heads were how compression changes were made. Another downside to this engine design, is milling the head and block results in retarding the cam timing. If available still, for ~$250 a guy makes a cam sprocket that's adjustable so you can fix the timing or even advance/retard the cam to your liking.

[milkovich]

Awesome, I've always wanted to mess with one of these.

Are you doing a TBI?

[TheSilverBuick]

Goal is MPI, a Turbo and as many RPM as I can cram into it.

A few stock engine specs:
250cid or 4.1L
3.875" Bore
3.53" Stroke
Rods 5.7" long
1.92" Intake valves
1.60" Exhaust valves
~8.5:1 Compression
Forged Rods (to be verified!)
Cast Crank

[67pete300]

Turbo exhaust manifold?

This isn't the guy I was thinking of, but here is one for sale on ebay:
http://cgi.ebay.com/ebaymotors/194-2...Q5fAccessories

I'm not sure it will work on the Pontiac. It's hard to tell from your pictures. The manifolds have a very similar shape but the exhaust port furthest aft looks different.

[67pete300]

Here's a video of the guy I mentioned. He is using the same type manifold as the ebay one:

http://www.youtube.com/watch?v=PLmUO...watch_response

330 Hp from a 250 on this run:
http://www.youtube.com/watch?v=jCT8s...eature=related

[milkovich]

Goal is MPI, a Turbo and as many RPM as I can cram into it.

Awesome, I wonder how hard it would be to make a cap girdle.

What kind of intake manifold are you thinking?