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Thread: 3.0L engine swap

  1. #441
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    Quote Originally Posted by Farrar View Post
    Yep, and it will have found new ways of falling apart in the meantime. Not much I can do about it, though.
    The gift that keeps on giving...hehe
    Rob Depew
    Tacoma, Wa
    '81 DeLorean 4877 Grey, Auto, 4 wheels
    The Ressurection of 4877......
    Now Accepting Donations to get her back on the road

  2. #442
    Owner since 2007 Farrar's Avatar
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    Drove out of the garage today so I could work on my daily driver. For fun I went around the block before pulling back into the driveway. Turned out not to be fun.

    I must have done some damage to the engine somehow, maybe when it got so hot. The 3.0L used to run as smooth as silk, and now it goes "PLUB PLUB PLUB PLUB PLUB PLUB."

    Dead cylinder? Crossed plug wires? Diagnosis will have to wait. And so will driving the thing. At idle it sounds like a lopey V8, but when I step on the gas the car *inches* forward and it's just ... embarrassing.

    At least I have a new a/c compressor on its way. Small improvements are better than no improvements.
    DeLorean status: It's complicated.

  3. #443
    Not a DeLorean Guru
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    Pretty much can guarantee you've lost compression on at least one cylinder. At best, blown head gasket and warped head, at worst, screwed up piston rings.

    My recommended plan of action:

    Perform compression test, record all numbers. Individual cylinder compression isn't as important here as it is all of them being close.
    Next, perform a leak down test. Individual cylinder leakdown amounts are very important here.

    Start researching on how to pull the heads, and looking for 3.0 head gaskets.
    -Mike
    1981 DeLorean, Carb LS4 swap completed
    1999 Corvette, cam/headers/intake manifold, 400 rwhp
    2005 Elise, stock
    2016 Chevy Cruze

  4. #444
    Owner since 2007 Farrar's Avatar
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    Quote Originally Posted by opethmike View Post
    Perform compression test, record all numbers. Individual cylinder compression isn't as important here as it is all of them being close.
    Thanks!

    I got to do a partial test earlier this week ...

    150 PSI on cylinder 1
    125 PSI on cylinder 2
    ... and then the tool broke.

    Once I'm done tracking down an electrical problem on the daily driver I can pull the DMC back into the garage and start working on it.

    I will note that Bill measured ~150 PSI compression on all cylinders before installing the engine. Variance was minimal. I will run the engine for twenty minutes and start the test again. If cylinder 2 still shows 125 PSI, then I'd say it is a good indication of what to check next. (Considering that the engine ran above 170F a few times, it may be time for a new head gasket. Stupidly.)
    DeLorean status: It's complicated.

  5. #445
    Administrator Ron's Avatar
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    Quote Originally Posted by Farrar View Post
    (Considering that the engine ran above 170F a few times, it may be time for a new head gasket. Stupidly.)
    Huh??? The thermostat is supposed to force the coolant up to its rating (most say ~190F, for the O2 sensor, etc.), not attempt to hold it there. Afterwards, it should run mid gauge (~220F) ideally.

    (Don't jinx it ;-)

  6. #446
    Owner since 2007 Farrar's Avatar
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    Quote Originally Posted by Farrar View Post
    (Considering that the engine ran above 170F a few times,
    Quote Originally Posted by Ron View Post
    Huh???
    Quite right! I meant to type 270F. Sorry.
    DeLorean status: It's complicated.

  7. #447
    Owner since 2007 Farrar's Avatar
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    Braved the mosquitoes to perform a compression test just now. (Daily driver seems to be doing OK, so the DMC Is back in the garage.)

    The engine was cold. I took each cylinder in turn and cranked for a second, then checked the gauge. When the reading stopped going up, that's when I moved on to the next cylinder.

    Cylinder 1: ~158 PSI
    Cylinder 2: ~184 PSI
    Cylinder 3: ~162 PSI
    Cylinder 4: ~156 PSI
    Cylinder 5: ~192 PSI
    Cylinder 6: ~152 PSI

    I've seen various sets of instructions online for performing a compression test, some of which say to warm the engine first and some of which don't. One set of instructions said to check each cylinder in firing order, the rest didn't.

    I can do a warm test tomorrow morning. The mosquitoes are swarming now, so I am done for the day.
    DeLorean status: It's complicated.

  8. #448
    Not a DeLorean Guru
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    Numbers are showing compression, which is good, but man, those differences of ~30 PSI aren't good. I would suggest that you go get a combustion gas tester from your local parts store. I'm willing to bet you have blown head gaskets.
    -Mike
    1981 DeLorean, Carb LS4 swap completed
    1999 Corvette, cam/headers/intake manifold, 400 rwhp
    2005 Elise, stock
    2016 Chevy Cruze

  9. #449
    Owner since 2007 Farrar's Avatar
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    Quote Originally Posted by opethmike View Post
    I'm willing to bet you have blown head gaskets.
    That's what I suspect, however will all of the other gunk in the cooling system I wonder if I might be better off checking for coolant in the oil rather than using one of those chemical combustion testers. But the combustion testers are less than $40 each, so I might as well go for it. Thanks for the suggestion.

    In the meantime, I will check compression again tomorrow after fully warming the engine, and then check the numbers against each other.

    I also need to get some oil so that I can do a "wet" compression test. Evidently what I have done is a "dry" compression test, and doing both is supposed to be diagnostically more useful.
    DeLorean status: It's complicated.

  10. #450
    Not a DeLorean Guru
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    Good choice doing the 'dry' test first. The wet test will raise compression numbers. I've personally found dry to be more useful, but that's my experience only.

    If you end up needing to pull the heads, I will walk you through it. It really isn't THAT bad.
    -Mike
    1981 DeLorean, Carb LS4 swap completed
    1999 Corvette, cam/headers/intake manifold, 400 rwhp
    2005 Elise, stock
    2016 Chevy Cruze

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