69 430 oil pressure in cooling system

I'm new to buick big blocks. I have a fresh 69 430 that has oil pressure in the cooling system upon initial start up. I suspect it may be getting in from the head gaskets. I have removed the heads and see nothing out of the ordinary. I have lots of experience building small block Chevy engines but have never seen anything like this. Please help with this conundrum.

 

We moved your thread to a better section for your issue.

 

Oil is being forced into the cooling system with significant pressure. When started the radiator immediately overflowed with fresh oil and coolant. I am a 25 year master technician and from my experience I'd say it full oil pressure being forced into the cooling system.

 

I did do a compression test and all was good. The engine pumped 3 quarts of oil from crankcase to cooling system in 15 seconds therefore I believe the oil leak must be under pressure

 

I agree with you Larry. I will install the heads again Monday with new head gaskets and prime it to see if maybe it was just the head gasket. The timing cover is brand new by the way.

 

So its transmission oil, NOT engine oil?
If so, then the transmission cooler in the radiator is leaking.

 

There is a coolant passage on the head side just 3/8ths of an inch from that oil passage.

 

It is 100 percent engine oil.

 

I have solid pushrods but the lifters are comp cam #910-16. They would definitely be able to take hollow pushrods. Like I said before this is the 1st 430 I have ever worked on so I didn't know if I could just plug those passages and go hollow.

 

Is there any way I have the heads on the wrong side? I did see a casting on the heads one has a 3 on it and the other has a 4 . The numbers are on the block side of the heads below the intake runners. I'm used to chevy 350s where it doesn't matter. Maybe I'm the cause of this issue.

 

The heads are interchangeable and not side specific.

 

Good. I'm glad that's the case.

 

I would explore what Bill said.
That's the only area I can think off too that has coolant and oil in close proximity to one another.

 

What are the casting numbers on the heads? If they've been sourced from a '72 or later 455, that maybe your issue as Buick changed water jackets. There are probably numerous threads on here. I've personally been a victim (hated those water pressure jokes).

 

This is true, you can use earlier heads on later blocks but not the other way around. The engine in my car now is 72 455 block and heads but the engine I'm building is a 70 455 block with 68 430 heads. I didn't ask that question when I made my earlier post sorry about that.

 

This is the original engine for my riv. I only rebuilt it because it had been sitting since 1973. The riv only has 16k on it. Someone had taken the carb off years ago and left the intake wide open. It's a true barn find. It was in a field 6 inches in the mud. The tags on the plate expired in July 73