Typical FE Oil into coolant issue.. Or not.

[Keith Stevens]

I have been having an issue with oil passing into the coolant system for some time. The shop that prepped the block did the oil passage modification.
The radiused adapter area, galley plugs, offset crank oiling orifices, oil pump at block. The two galleries were drilled to 7/16" at the oil filter adapter.
Do either one of those passages intersect or parallel to a water jacket with proximity close enough to have been compromised?

[WConley]

Keith -  It's most likely one of the oil galleries going up from the cam bearings to the heads.  These have a history of cracking over time.  People have fixed them by pressing pushrods (ends cut off) with epoxy all the way down to the cam bearings.  You might have to chase out with a drill before doing it.

Somebody who's actually done it will probably chime in...

[Keith Stevens]

I have a copy of the bulletin on that modification.  That was my guess too. However, it crossed my mind that the feed galleries had also been enlarged slightly.

[thatdarncat]

Here’s the bulletin info, for those that haven’t seen it, from the files section on the FE Fanatics Facebook page.

[Keith Stevens]

I have that bulletin too.  I know many have suffered this annoying issue over the years. I just wanted to confirm there are no water passages near the oil galleries that are at the front of the engine. That would rule out the issue coming from enlargement of those passages.

[jayb]

There is no water around the oil hole coming from the pump to the oil filter adapter.  However, at the top of the oil hole that goes from the adapter up to the top of the engine, there is some proximity to the water jacket.  This hole is drilled in two different steps, one hole from the oil filter adapter about 2/3 of the way up the block, then another hole is drilled at an angle from the valley area down to intersect the first hole.  The intersection of the two holes is circled in red in the picture.  I had an aftermarket block that leaked in the that oiling passage once.  However, even on a 390 block that is a pretty big passage, and it is not normally drilled out.

[Keith Stevens]

That passage was drilled to 7/16. It was 3/8" if memory serves me correctly.  I gather a cracked rocker feed can make for pretty messy radiators?

[jayb]

That passage was drilled to 7/16. It was 3/8" if memory serves me correctly.  I gather a cracked rocker feed can make for pretty messy radiators?

Keith, I think you are mistaken about that.  I just checked an unmodified 390 block and that passage is already 7/16", maybe even a little bigger.  Maybe it was drilled out to 1/2"?  That would be unusual; radiusing the hole is the norm, not drilling it out.

And yes, a cracked rocker feed can certainly leak some oil into the coolant...

[Keith Stevens]

Thanks, Jay.  Enough to leave black oil floating on top of the water in the radiator?  I only run distilled water.

[Cyclone03]

Don’t have the problem yet,just prepping for it.
I’m running a hydraulic roller with pushrod oiling to Brent’s roller rockers can I just plug the passages near the cam bearings. The rockers do allow for shaft oiling.

[jayb]

Thanks, Jay.  Enough to leave black oil floating on top of the water in the radiator?  I only run distilled water.

Easily enough to leave oil on the surface of the water in the radiator...

[Keith Stevens]

If I run water wetter or coolant it turns into nasty milk-shake looking garbage. If I run straight distilled water it floats on top and stays black.