[67Lemons]

Also, for me I’d ditch that carb, 650 is not big enough for a Pontiac. You’d probably gain more performance, real and seat of the pants with just a carb swap once you take care of the head gasket without spending the money on new heads or even porting your current ones IMO.

[vamman1]

Originally Posted by 67Lemons

Also, for me I’d ditch that carb, 650 is not big enough for a Pontiac. You’d probably gain more performance, real and seat of the pants with just a carb swap once you take care of the head gasket without spending the money on new heads or even porting your current ones IMO.

Wow; what size? Discovered the engine is bored .040 over

[vamman1]

Still battling this.
Reinstalled head with new bolts to 100ft lbs and Felpro1016 gasket.
Surfaces cleaned for operating room....

I must be too stupid to get exact TDC because can not stop air sound coming from valley from leak down test. Tried the same on Cylinder 3 that pressure tested at 150psi and same air sound.

just rocking the crank between TDC I can not stop the sound of air - pretty loud whoosh at 60psi
Clylinder bore is super clean

Thinking now I have to pull that piston on Cylinder #1?
Someone once said hit those valve springs on #1 to make the valves seat from potential carbon buildup?

Engine will kick with air applied to cylinder 3 and not right on TDC but cylinder 1 will not

[mysticmissle]

did you look at the valves while head was off? any pictures? lash too tight or bent valve/bad seat?

[steve25]

Pack number one intake port with paper towels, does cranking the motor with the starter then move / blow the towel out?

[vamman1]

[vamman1]

Originally Posted by steve25

Pack number one intake port with paper towels, does cranking the motor with the starter then move / blow the towel out?

I've got the valley pan off. Can i crank with just the head and rockers back on?

[mysticmissle]

Yes just be careful fuel pump doesn't spray all
Over

[Stan Weiss]

What does the valves sealing have to do with the air leaking from the valley?

Stan

[mgarblik]

I just read your entire thread. Based on the information I was able to gather, you most likely have a broken ring land, stuck piston ring (s) in cylinder #1. A blown head gasket rarely effects just 1 cylinder, almost always 2 are effected, side by side. But the loose head bolts you found, anything is possible. Cast pistons are particularly prone to detonation damage. I mention this because you mentioned 93+ octane gasoline was hard to find in your area. That leads me to believe some detonation was happening and it doesn't take much to kill those pistons. To me, it looks like a disassembly is in your future. Once disassembled, you can figure out what cam is actually in there and the condition of the pistons and ring lands. All I can say concerning aluminum vs iron heads is aluminum is more tolerant of lower octane fuel. Good luck with it.

[Skip Fix]

As far as heads iron vs aluminum take one of each and pick them up and put them up on a flow bench. The one that does not hurt your back also probably flows better too-and it is not the iron one!

[ta man]

Originally Posted by Skip Fix

As far as heads iron vs aluminum take one of each and pick them up and put them up on a flow bench. The one that does not hurt your back also probably flows better too-and it is not the iron one!

I can remember pulling and swapping cast heads in my younger days. Now with my funky back ..no way bending over a fender and lifting a cast head! I would probably use my picker!

[steve25]

I can tell you’ve never had the joyfully experience of setting up an international 392 head or a 671 Diesel head in a milling machine! :-)

[steve25]

I can tell you’ve never had the joyfully experience of setting up an international 392 head or a 671 Diesel head in a milling machine! :-)

[blueghoast]

Originally Posted by vamman1

Attachment 664441

Attachment 664442

Wow didn't anyone notice the burnt exuast valve in the picture.
Think that might have something to do with it?

GT

[vamman1]

Originally Posted by mgarblik

I just read your entire thread. Based on the information I was able to gather, you most likely have a broken ring land, stuck piston ring (s) in cylinder #1. A blown head gasket rarely effects just 1 cylinder, almost always 2 are effected, side by side. But the loose head bolts you found, anything is possible. Cast pistons are particularly prone to detonation damage. I mention this because you mentioned 93+ octane gasoline was hard to find in your area. That leads me to believe some detonation was happening and it doesn't take much to kill those pistons. To me, it looks like a disassembly is in your future. Once disassembled, you can figure out what cam is actually in there and the condition of the pistons and ring lands. All I can say concerning aluminum vs iron heads is aluminum is more tolerant of lower octane fuel. Good luck with it.

the cylinder did hold fluid for 24hrs with a 50/50 acetone/ATF soak.
So I still have 70 psi and this is driving me crazy.
Someone mentioned a burnt valve?

[vamman1]

Adjusted the rockers, replaced the head gasket.
175psi on 7 cylinders..... 70psi on Cylinder 1

[vamman1]

Pressure test this morning now 40psi on cylinder 1 when I let the rockers go loose.
Idk

[vamman1]

Lightly tapped on top of valve with the rockers loose and out of the way...
Now 25psi........