Sure sounds low.

 

I have no clue what kind of timing set is on that ohc engine but I'm pretty sure that advancing the cam would make wonders.

 

I have no clue what kind of timing set is on that ohc engine but I'm pretty sure that advancing the cam would make wonders.

I have no clue what kind of timing set is on that ohc engine but I'm pretty sure that advancing the cam would make wonders.

No offense, but when I consider what I started with, I'm already working with wonders. BTW, have you ever seen or worked on one of these scarce OHC 6's? I've never seen another other than the ones I own, so I'm always willing to listen to experienced help. Your suggestion has merit, as it seems to work on other more conventional engines,
Thanks
Bob

 

Seen them in magazines, shows in 80s. Was a cool option, GTOs get the lime light. there are FB groups just for OHC 6. I'd check them out, probably get some invites to shows. PHS ...Pontiac Historical Society?

 

No offense at all Bob and no I haven't worked on Pontiac ohc engine but yes I have seen one.
An engine is an engine and it doesn't know what is scripted on the valve cover, all I'm saing is that to me 140psi cylinder pressure in fresh build sounds pretty low.

 

Running an engine on an engine stand allows checks for leaks & not much else.
Everyone is concerned about low cranking compression we have a cart before the horse scenario here its a fresh build, take the d a m n thing out for a ride & bed the piston rings in.
One of my 13 to 1 mills only pumped 195 after the rings were bedded in on a engine dyno, it had a big cam with a lot of overlap.

 

Except cold cranking a fresh engine also tells us if there is any potential or real problems. Ultra low cylinder pressure can be a problem. It would not be the first time an engine builder made a mistake. Hell it would not even be the first time an engine builder made a mistake on one of Bob':s engines.

 

Just because something is rare or scarce does not make it desirable.

 

Like I posted in your other thread on the low compression test-have you tried a different compression tester or at least replaced the leaking schrader valve in the one you're using to see what numbers you get?

 

Nope. It is what it is. If it’s broken, I’ll fix it. I have two more in the wings.

 

Speaking of 6 cylinders:

I once ran a compression check on a '74 225 Plymouth slant 6 with about 50k on it. It was either 8:1 or 8.5:1. It pulled numbers slightly better than your OHC6.

I agree with Robert on the readings.

 

By the sounds of it your close to cruising around

 

Bob, I don't think anything in your engine is broken. All I'm trying say is that I really think that advancing the camshaft would really help. I've done that mistake and messed up timing set installation the result was that camshaft was retarded and due that cylinder pressures were really low and while the engine (350 sbc) did run and sounded good it was a dog to to say the least.

 

It's ready.....

 

It's interesting no one has asked whether I'm using a domed or flat piston. I believe that due to valve travel, they used q "D" shaped .060 recess;. (see pics)
The cam that was on there looked good. It may have had the head overhauled. So they cleaned it and reinstalled it. Everything was replaced in the order it was removed.
Machinist used 1968 Pontiac specs to put it together, and mechanic used the thinnest head gasket he could find online.

 

Swap Meet: funny... now seeing these Pontiac parts. Was told big club in Oakland California.

 

If pistons are like the one on bottom left corner there might be some problems with cylinder pressures😄
Seems like the engine has belt driven camshaft...very modern stuff for mid sixties.

 

Cam is definitely belt driven. I thought you knew that. My piston tops will maintain better compression, but I am using different pistons in each of my two engines. Ohe has a "D" type recess that may cause a lower compression than the other that has a flat top but with valve clearance notches.

 

The flat top with valve reliefs were used in the higher compression quadrajet version of the OHC six the dished version in the lower HP version.Then often with most standard replacement pistons they could be lower in the hole than the originals.Like was mentioned you could double check the cam timing which is probably set correctly.Then put miles on it & with that good of a cylinder leak down test there is nothing wrong with the rings or valve sealing.Ive had the head off of one many years ago but don't remember the circumstances.I thought they were a unique engine back then but didn't have enough cylinders or nearly enough cubic inches to be of much interest to my 20 something year old self.Having said that kind of nice to see one saved instead of made into a fake GTO.I might have elected to convert to a 4 speed though.Should be a nice car when done.