Customs Engine Vote 1948 Pontiac Streamliner

389 / 421 with tri power and the most modern automatic that will bolt up. Gary

 

Mid 60's Pontiac OHC 6...had one in my 40 Pontiac...fit like a glove, and went like hell...

 

Get the Hi-Po version.
It was in the LeMans Sprint
It had a 4 barrel and I think
higher compression.
Those OHC's could rev!

 

Hi everyone. It's me again. So to update everyone. In hindsight I should have pulled that hunk of cast iron and swapped it out with a Pontiac v8.

Needless to say I'm a softie for the old motors that you don't see much so I dumped 6k into the rebuild which included 2 sleeved cylinders and everything +060. dropped it all back in and low and behold we are baffled.

It dumps antifreeze into the back three cylinders.

Two head gaskets later we still cannot figure it out.

Head was magnafluxed no cracks
Block was pressure tested (wonder how they do that. Better ask)
Head was decked and mated to block all in spec
Had thread sealeant and the head bolts
We did not apply any other sealeants to the head gasket as the gent at Pontiac parts said if you need that it's a sign of something else off.
About ready to ghost dive it off the nearest cliff.
Any ideas?
Help

 

I'll ask the obvious...did the shop guy sonic check the cylinders before boring to 060?
And, which holes were sleeved?

.

 

Too late now I guess, but I would have done a 389/400 Pontiac. Its a HUGE, HEAVY car, torque is your friend, and another very big factor in its favour is that Pontiac motors are not as popular in the traditional hot rod world as Olds, nailheads or early cads, and because of that, I notice vintage speed equipment for Pontiacs is in less demand, and a bit cheaper than the traditional "big three".

 

So, you still have the original problem from '79.

Shame too. Those Poncho straight 8s could pull trains and last hella long time.

It'd be a helluva crack in the block to bridge all 3 cylinders.

 

where are the sleeves in relationship to the leaking cyls? What is the machine shop's position with regard to all of this?
For 6 grand someone ought to be doing something for you!

 

They're working on it and covering the costs.

Seems we're going to Copper coat the gasket which we've been installing dry.

Sleeved cylinders are 2/7

A gent that worked at Eggie Machine said the head gaskets need To be coated. At this point. Whatever works. Should have slammed a new plant in the beast. Hindsight.

 

I am no expert here. But I do like to put compressed air into a cylinder to see where it's getting out. Sort of like leak down test. If water is getting into the cylinders I guess air could get out. This would tell you if it was a head gasket leaking. I don't know if a Pontiac could leak water from the intake into the cylinders. Maybe there

 

I’ve been thinking about swapping out the straight eight for a 350, was it a huge process?

 

Old post but does anyone that’s done a v8 swap in a 1948 Pontiac know the configurations for motor mounts?

 

you have answers on your other thread.