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

Discussion in 'The Hokey Ass Message Board' started by Roothawg, Apr 7, 2016.

  1. lumpy 63
    Joined: Aug 2, 2010
    Posts: 2,603

    lumpy 63
    Member

    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.
     
  2. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    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.
     
  3. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    The upper hose started coming off too so the whole system is just getting too much pressure or so it seems.
     
  4. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,523

    Roothawg
    Member

    Interesting.
     
  5. wheeltramp brian
    Joined: Jun 11, 2010
    Posts: 2,551

    wheeltramp brian
    Member

    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
     
  6. Moriarity
    Joined: Apr 11, 2001
    Posts: 30,774

    Moriarity
    SUPER MODERATOR
    Staff Member

    or there is still a problem with the cylinder heads or head gaskets?
     
  7. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,523

    Roothawg
    Member

    That's the part I worry about.
     
    warbird1 likes this.
  8. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    Hmmm. I hadn’t thought about that. I may order an exhaust gas tester kit.
     
    Moriarity likes this.
  9. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    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.
     
  10. wrenchbender
    Joined: Sep 5, 2007
    Posts: 2,337

    wrenchbender
    Member

    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
     
    Barrelnose pickup likes this.
  11. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    . Thank you. I’ll give that a shot
     
  12. 42merc
    Joined: Dec 19, 2010
    Posts: 894

    42merc
    Member

    I 've used Felpro head gaskets on several early Cad motors, NEVER a problem. Gaskets installed clean & dry, no sealer ever.
     
  13. Roothawg
    Joined: Mar 14, 2001
    Posts: 24,523

    Roothawg
    Member

    I’m worried that whatever caused the original head to crack (getting hot), may have migrated to the block.
     
  14. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    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…..
     
    Roothawg likes this.
  15. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    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.
     
  16. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    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).

    E765A6E5-FED9-43D2-BB9B-C898AE94871E.jpeg 9DCA4CB4-C059-4FB8-A992-7ACD9E5B20D0.jpeg FD12B6D3-2DB2-47E0-818C-B50AEEF2BB65.jpeg AE7CAD5C-CD96-4BB0-99AE-BFD9582950AD.jpeg 06EE33BC-2863-4C7F-B6B0-A422DEAB9A7D.jpeg EB5E5711-6CA7-4423-AEEB-7F2D092B2BF3.jpeg
     
    Last edited: Jan 5, 2023
    kadillackid likes this.
  17. Moriarity
    Joined: Apr 11, 2001
    Posts: 30,774

    Moriarity
    SUPER MODERATOR
    Staff Member

    I enlarged the pics for you, always select full image when posting pics... man that is a lot of pitting, can you tell by looking at the gaskets which cylinder was leaking??
     
    kadillackid likes this.
  18. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    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.
     
  19. lumpy 63
    Joined: Aug 2, 2010
    Posts: 2,603

    lumpy 63
    Member

    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.
     
    Dick Stevens likes this.
  20. wrenchbender
    Joined: Sep 5, 2007
    Posts: 2,337

    wrenchbender
    Member

    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
     
    warbird1 likes this.
  21. sheparj2
    Joined: Dec 19, 2018
    Posts: 53

    sheparj2
    Member

    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?
     
  22. lumpy 63
    Joined: Aug 2, 2010
    Posts: 2,603

    lumpy 63
    Member

    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.
     
    Last edited: Jan 6, 2023
  23. lumpy 63
    Joined: Aug 2, 2010
    Posts: 2,603

    lumpy 63
    Member

    Also make it easy on yourself and get a Best gaskets 3610S neoprene rear main seal.
     
    sheparj2 likes this.
  24. #3 and #5 do not look good... that block needs to be decked, if there's enough meat left.
     
    sheparj2 likes this.
  25. cretin
    Joined: Oct 10, 2006
    Posts: 3,066

    cretin
    Member

    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?
     
    Last edited: Jan 15, 2023
  26. They should be interchangeable; other than the vacuum pump and possibly the drive on the early ones.
     
    cretin likes this.
  27. rod1
    Joined: Jan 18, 2009
    Posts: 1,324

    rod1
    ALLIANCE MEMBER

     
  28. rod1
    Joined: Jan 18, 2009
    Posts: 1,324

    rod1
    ALLIANCE MEMBER

    Kyle, I'll have one. Let me search.
     
    cretin likes this.
  29. rod1
    Joined: Jan 18, 2009
    Posts: 1,324

    rod1
    ALLIANCE MEMBER

     
  30. rod1
    Joined: Jan 18, 2009
    Posts: 1,324

    rod1
    ALLIANCE MEMBER

    Yup ,found it.
     
    WTF really and cretin like this.

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