Hot Rods Let's talk Cadillac 331's, 365 and 390's

Some of the cheapie water pumps I remember looking at didn't have a lip on the pump inlet so theres nothing to stop the hose from blowing off under pressure.

 

I never ran it long enough to know. The radiator is new. I think I went with a remanufactured water pump but I don’t recall. I think I may try to drill holes in the thermostat and see if that helps.

 

The upper hose started coming off too so the whole system is just getting too much pressure or so it seems.

 

Interesting.

 

Perhaps your hoses are too large in diameter or you don't have the clamps tight enough or your radiator cap is faulty in building way too much pressure just thinking out loud

 

That's the part I worry about.

 

Hmmm. I hadn’t thought about that. I may order an exhaust gas tester kit.

 

Leak test is showing combustion gasses in the coolant…. Compression check still seems a bit low on left side. Should I have used some kind of sealant with the felpro gasket? I got mixed instructions on their website.

 

I have a few things to help first thing remove upper hose and thermostat and housing take water pump belt off fill cooling system up to T stat level start engine and let it idle if it has bubbles coming from one side or the other then it has compression in coolant system this test will determine which side or maybe even both sides that has an issue if it is the same side as before then when you pull the head make sure the deck on the block is flat and I’m guessing you had the new head surfaced so that it was a known flat surface if not that is a must next you may have to make a deck plate and pressure test the block I have had engines in past develope a pinhole in the cylinder and cause this issue it is rare but does happen more than likely it’s a issue with a surface that is not flat and a gasket leak

 

. Thank you. I’ll give that a shot

 

I 've used Felpro head gaskets on several early Cad motors, NEVER a problem. Gaskets installed clean & dry, no sealer ever.

 

I’m worried that whatever caused the original head to crack (getting hot), may have migrated to the block.

 

I had the whole motor rebuilt but it was a long process with many flaky dudes involved…. I’m debating just yanking the motor at this point and taking it to a big engine rebuilder a few hours away and hopefully just get it done once and for all…..

 

I did as wrenchbender said. Took off the thermostat housing, started it up and sure enough bubbles were coming from the drivers side only. When I shut it off bubbles started coming from both sides. I didn’t oil the underside of the head bolts before I torqued them. I’m tempted to loosen them, oil the undersides and retorque. I don’t really have much to loose at this point.

 

Do you guys think these imperfections could be causing the leak? The surface doesn’t seem warped but definitely a lot of pitting (rust I assume).

 

Ok. I think I fixed the pictures. No, I really can’t but I didn’t run it very long. Maybe 30 minutes. I took the whole engine back to the rebuilder but he’s just lost.

 

That block really needs to be decked, but first you need to measure how far down the pistons are at TDC to see how much you can cut it.

 

First thing is that block needs to be decked it has way to much pitting to expect a gasket to seal my big concern is the area in the 5th pic but I will look at my extra block when I get home tonight to see what that hole is for as it been awhile since I looked that close and it may not matter

 

Thank you guys. I appreciate the input. I actually found another 390 block on craigslist. I’ve never assembled a bottom end before. If move all my components to a new block can I reuse the rings or will I need to replace a bunch of stuff even though it’s all new?

 

Considering the really low run time you should be ok reusing the rings as long as you didn't overheat it . The bearings should be fine too just inspect everything really well. I am glad you are thinking of building it yourself because honestly the last builder had no business assembling that engine with those nasty decks.

 

Also make it easy on yourself and get a Best gaskets 3610S neoprene rear main seal.

 

#3 and #5 do not look good... that block needs to be decked, if there's enough meat left.

 

Does anyone have a spare 331 oil pump they would be willing to part with? Or know where I can find one?
It's '49 if it matters.
No problem if it needs rebuilding.
It shouldn't be too long before the machinist is done, and unfortunately, I didn't have a pump in my stuff.

Are oil pumps interchangeable between 331, 365, and 390?

 

They should be interchangeable; other than the vacuum pump and possibly the drive on the early ones.

 

Kyle, I'll have one. Let me search.

 

Yup ,found it.