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Thread: Cylinder Bore porosity

  1. #1
    Mitsu booster
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    Cylinder Bore porosity

    So got the head/turbo/manifold assembly off my Turbo II for my GLH-T2 engine rebuild and encountered what looks like some porosity in #2 bore. I'm just curious to know what thoughts are if this is a deal breaker before I get the cylinders bored. In my industry you run the risk of opening up into more porosity...which I guess would be a risk here too. Doesn't appear to be in the other bores. If it isn't a dealbreaker, what's the opinion it'll clean up at 0.020"? I can't catch my nail in it, but you can certainly feel it.

    I set my bore gauge up to zero at 3.440-inches and the bores are measuring around .005 to .0065-inches larger...top, middle, & bottom in and in two measurements 90 degrees, and this doesn't show increased bore at this spot. So, it's pretty close to the original factory bore (87.5mm = 3.445-inches). Granted that was with the pistons still in, just moved to bottom of the stroke, and without a torque plate bolted up. The transmission is still bolted. If memory serves the prior owner mentioned the engine/transmission came out of an 87 Shelby Z with roughly 60k on it...and we've only put another 12k on it since (2010). So makes sense it would still be close. One thing that's been happening the last two summers as when I get into boost the oil dipstick pushes out.

    I would like to get my pistons on order and was planning on 0.020" forged pieces. Should I just wait till after the boring to confirm it cleans up or stick my neck out and just pull the trigger. I fear if I wait...the car will be out of commission until next spring.

    We'll see if this picture shows up.

    [IMG]file:///E:/Photos(Personal)%20from%20My%20(&others)%20Cell%20 Phone/2024%20Photos/IMG_4071.JPG[/IMG]

  2. #2
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Cylinder Bore porosity

    Your photo didn't come through. You can email it to me and I can post it if you want.

  3. #3
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Cylinder Bore porosity

    Here is the photo.

    Click image for larger version. 

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    That does look like it sat with some water in it at one time. I would probably see what the machine shop thinks about that one.

    ETA: Not really sat with water, but something ran down the cylinder and puddled up enough to make the pyramid shape at the bottom when it collected up at the ring.

  4. #4
    Mitsu booster
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    Re: Cylinder Bore porosity

    Yeah, I texted him and he got back to me later today and said it looks a tad deep so he would like to test bore it and can fit me in around the end of July. So will more than likely wait till that gets done before I pull the trigger on the pistons. Just seems like the longer I wait the pricer they get!!

    Not sure, this is the first time I've pulled the head, but found it strange the top of the pistons and chambers in the head were all rust colored. Some of the crack's b/w the seats look to be below the valve seats, but never noticed any coolant going out the exhaust. The head gasket looked a little hammered b/w 1 and 2 and 2 and 3 but didn't see any path from water jackets to the cylinders. Thanks for the help getting the photo uploaded and the comment.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Cylinder Bore porosity

    No problem. I'm sure your machinist will talk to you about it, but they usually cut the bores to fit the individual pistons, so he'll probably want those if he ends up deciding that the block will be good enough to use.

  6. #6
    turbo addict
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    Re: Cylinder Bore porosity

    Cracks continuing below the seats will find a way to water for sure. I'd be looking for a new head, or plan on a huge bill from the machinist to repair that. It won't be cost effective to fix this unless you're doing all the labor yourself.
    Hard to say, but that pitting looks to be deeper than .020" The block may still be salvageable, but I seriously doubt it will completely removed with a .040" overbore.
    Todd

  7. #7
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    Re: Cylinder Bore porosity

    Thanks Todd, I had already got a Stage 2 head from FWDPerf. so won't be using the head I pulled off. Strange thing about that is I noticed it didn't have the typical turbo head cross-drilling on it. So, I'm curious to know if that's not wise to run without it. I would think a head of this price would have that done to it!! I'm planning of getting the Reeves kit (?) that flows coolant to that 4th cylinder, so maybe that'll help offset that?
    Yeah, I'll certainly know more after the machine shop does a test bore down that cylinder...hopefully if it doesn't at .020", it will at .040"...which I believe is about the limit for this block. I was going to pull the trigger on the pistons but will wait and see what/if this cleans up. Otherwise, will need to rethink the project. I've got a spare block and crank, picked up with other car buys...so maybe that'll be good to go.
    Mike

  8. #8
    Supporting Member Turbo Mopar Contributor 2.216VTurbo's Avatar
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    Re: Cylinder Bore porosity

    Pro tip. Order 5 pistons, when ever I have a set made I order 5. Twice in the last couple decades I've used piston #5 when one got hurt. It's really not that much more bux.

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  9. #9
    Mitsu booster
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    Re: Cylinder Bore porosity

    Quote Originally Posted by 2.216VTurbo View Post
    Pro tip. Order 5 pistons, when ever I have a set made I order 5. Twice in the last couple decades I've used piston #5 when one got hurt. It's really not that much more bux.
    Thanks...very good tip. Ironically, I had a set of JE pistons on my 87 Shelby Z, and one of them got the top melted a little...so would have been handy to have the 5th one.

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