I had two grenade on my 28 years ago at the same time. Ended up being bad octane fuel. That really knocked a hole in the Summer. :(

You must have one, oil temps would go thru the roof without one in the system somewhere. You sure on this?

Yes sir, I am looking at ways of getting heat into the oil. It is probably due to the motor being raw water cooled. That is with oil pressure between 45-60 psi at idle/WOT respectively.

I am getting ready to tear off the manifold now to check for a water leak at the coolant crossovers.

most small blocks don't come from the factory with an oil cooler

Found the source of the milkshake.
 

I found the leak! There is a 2 1/2" long crack under the intake running parallel with the deck of the block and the lifter valley. This is common with older 350 blocks. I am sure I magnafluxed the block prior to machining it. Either I missed it initially, it cracked when torquing down the heads, or some other unknown force I am not aware of.

I am performing emergency surgery as we speak... I will post before and after pictures when I am done with the repair. The process involves drilling, tapping and loctiting cast iron pins along the crack until you reach the ends of the crack. It should be a permanent repair. I will keep everyone posted. I should have it back out on the water tomorrow.

Don't bother get another block your fix won't last if it works at all

Why do you say that? Do you think the leak will continue? Or do you think it will crack somewher else? Have you experienced the same problem before?

Thats a sketchy fix at best. It may do the job in a car engine but your taking chances in a marine enviroment. It's that constant 4000-5500 rpms that really tears $hit up! Good luck, I hope it works for you.

No chit, guess you can always learn something here. Still makes me wonder how the oil temp dosen't just climb out of site without one, dosen't seem like there would be enough air movement thru the bilge to control it. Well, I stand corrected.

Make that 6,500 - 7,500 for this one. If I was starting with a raw block I would definitely scrap it and find a new one. This block has close to 30 hours worth of machine work. I have to at least attempt a repair. I should have it back out on the water today and I will let everyone know how it goes.

BTW, I pressure tested the repair up to 40 PSI after it was complete and found that the crack extended further than it actually appeared. I went ahead and extended the repair until it was out of sight. Hopefully I got to the end of the stress riser... We will see how it holds up.