The Pontiac OHC Six

[Tazracing]

Re: The Pontiac OHC Six

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

most pontiacs are cast rods (superduty being the forged)
why you think the inline 6 would have forged?

[TheSilverBuick]

Re: The Pontiac OHC Six

Thanks again Pete, I'll have to check them out when I get home from work

Intake and such I figured I'd have to make but will cross that bridge when I get to it. Part of my motivation to get a welder and learn to weld ;D


I was looking up some Turbo Buick info for comparison sake, figuring the Buick group gets pretty decent power out of roughly the same displacement with a turbo.


Buick: OHC:
3.800" Bore 3.875"
3.40" Stroke 3.53"
5.96" Rod Length 5.7"
1.625" Intake Valve 1.92"
1.425" Exhaust Valve 1.60"

Quite a bit larger valves in the Pontiac head, though the head itself is not a cross flow design, hopefully it's still good for air flow.

most pontiacs are cast rods (superduty being the forged)
why you think the inline 6 would have forged?

Read it several places and on builds. I guess I'll know when I pull the oil pan.

[squirrel]

Re: The Pontiac OHC Six

deep skirt block...cap girdle could be interesting

[TheSilverBuick]

Re: The Pontiac OHC Six

deep skirt block...cap girdle could be interesting

Go on....... Remember I look at rocks for a living here....

[squirrel]

Re: The Pontiac OHC Six

Actually the deep block makes it easier if you build one that sandwiches between the block and oil pan. Need to get the pan off and see where the bolt heads on the main caps sit, relative to the oil pan surface. If they're about even then it would be good.

But you'd probably need to be making stupid power to need a girdle, it has 7 main caps.

[1988montecarloss]

Re: The Pontiac OHC Six

theres a 66 lemans that drives around here in the summer with an ohc 6cyl in it.

any idea what you want to put this motor in yet?

[squirrel]

Re: The Pontiac OHC Six

69 firebird, of course!

[TheSilverBuick]

Re: The Pontiac OHC Six

69 firebird, of course!

Yes! :D

[milner351]

Re: The Pontiac OHC Six

Girdle?

no problem - Jim just bought a MILL! ;D

[CTX-SLPR]

Re: The Pontiac OHC Six

Why am I seeing imatation sidedraft webers as TB's on this thing???

[milkovich]

Re: The Pontiac OHC Six

Way too expensive but I'm loving these: http://extrudabody.com/Products/ITBs.html

I'm not sure the complexity would outweigh the benefit on a turbo engine though. An ebay stock V8 throttle body for $25 would be the right price.

[squirrel]

Re: The Pontiac OHC Six

that's a neat setup....

[TheSilverBuick]

Re: The Pontiac OHC Six

Bringing this conversation over to this thread.

just leave it stock.. get it to zero deck and flat tops,

Zero decking will retard the cam (down side to the current design!), just take enough of to make it flat. I do plan on purchasing a modified cam sprocket that allows the cam timing to be modified/degreed.

Randal, have you picked out a turbo yet? or a power goal?

No and no. I actually am not so concerned about peak HP numbers as I'd rather see higher rpm and use the turbo as an airflow crutch to get there, letting the HP fall where ever it does. Kinda why I have the rod/stroke ratio thread going.

7 mains...Nice.

And a deeper skirt block.

Squirrel, or anyone, I read something about the Chevy cranks being fully counter weighted and the Pontiac's not being, do you know what that specifically means? I also read something about the Pontiac 250 having an improved crank over the 230 crank, though not sure exactly what those improvements were, possibly more counter weights?

[dieselgeek]

Re: The Pontiac OHC Six

Randal, have you picked out a turbo yet? or a power goal?

No and no. I actually am not so concerned about peak HP numbers as I'd rather see higher rpm and use the turbo as an airflow crutch to get there, letting the HP fall where ever it does. Kinda why I have the rod/stroke ratio thread going.

Yeah but, it's a turbo application - is it going to make 900hp, 700hp, or 500hp? I vote for lower numbers, it'll be more fun on the street at 500ish hp. Are we shopping for junkyard turbos yet? intercoolers? Going to need / want a blowoff valve.

[Tazracing]

Re: The Pontiac OHC Six

Bringing this conversation over to this thread.

just leave it stock.. get it to zero deck and flat tops,

Zero decking will retard the cam (down side to the current design!), just take enough of to make it flat. I do plan on purchasing a modified cam sprocket that allows the cam timing to be modified/degreed.

[

zero decking it will retard gthe timing if you deck the block..
not if you use custom pistons, or dome pistons that are flycut