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Thread: New 350 build leaking

  1. #1
    Fuel Injected! Resin's Avatar
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    New 350 build leaking

    Hello again,

    I am relatively new to engine building. I've done plenty of work on existing engines but my experience with new builds is in development.

    I just finished putting a brand new build in my 1989 Firebird. It went from an L03 to a roller 355 w/ vortec.

    My question is, should I see any leaks? Is it normal for a new build to leak a little bit? I've got about 150 miles on it at this point.

    How hosed am I?

    1.jpg2.jpg3.jpg4.jpg

  2. #2
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    Not normal at all. Are those leaks from the LH head gasket area? What year is block? You might need to tighten a pipe plug in the LH side of blockbehind the cylinder heafd.

  3. #3
    Fuel Injected! Resin's Avatar
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    Unfortunately, each of those 4 pictures is a different corner of the block. Both left and right heads, front and back. It appears to be coming from the head to block mating surface on all four corners. The block is a marine engine from 1995 I think. I don't have the casting number off hand but I can get it. I had a machine shop go through it and bore it 30 over due to some rust from water sitting in one of the cylinders. It's a good shop and I trust their work. They decked the block and heads for me so there should not be any warpage to worry about.

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    It occurred to me just now that I might want to clean it off and see if it's actually leaking. A couple of weeks back, I had a heater hose burst. I suppose it's possible that some coolant ran down the corners of the block. I'm going to wipe it down and see if it comes back before doing anything drastic.

  5. #5
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    Definitely hose everything off before making any decisions.

    Do you know what was installed for a head gasket? Steel shim type or composition?

  6. #6
    Fuel Injected! Resin's Avatar
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    I used a composite gasket from Enginetech.

  7. #7
    LT1 specialist steveo's Avatar
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    that's really fresh oil, buddy. you must have pinched or damaged a gasket during installation, mistorqued something, missed some RTV'd corners that some GM gaskets require, or had mating surfaces not...uh...mating. clean it, run it drive it, and check again, but i think that engine is coming back out to be re-gasketed.

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    That is really odd all four corners have leaks. Oil through the head is merely a static drain back into the motor. Water on the other hand is pressurized. Doesn’t appear to be water though. Is it blowing out the intake valley and finding a leak path, if not the head gaskets would be highly suspect and didn’t seal properly.

  9. #9
    LT1 specialist steveo's Avatar
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    when i see leaks from a fresh engine on more than one surface it must be some fundamental issue

    damaged or incorrect gasket(s)

    mistorqued fasteners

    machinist needs to be taken out back for "a chat"

  10. #10
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    Lots of maybes but it's likely something simple.

    What head bolt torque value did you use?
    Can you see any leakage from under the valve covers?

  11. #11
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    Hiya's,
    I'll throw this out there...I had a set of EngineTech head gaskets leak water as I was filling the radiator, I was hoping a couple heat cycles would do something, nope. The fire ring wouldn't compress enough for the rest of the gasket seal to work :(
    -Carl

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    did you put thread sealant on all the headbolts? they all go into coolant...

  13. #13
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    Quote Originally Posted by tayto View Post
    did you put thread sealant on all the headbolts? they all go into coolant...
    Umm not on the blocks I have. There are multiple blind holes. I always blow the blind holes out to prevent cracking the block.

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