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  1. #1
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    Default My continuing 383 saga..........

    Hey all. Is this enough clearance for a 383 crank? I can only just fit a 30 thou feeler gauge between the block and the nut.

    COME Racing in this video say that they generally aim for 50 to 60 thou clearance; so basically double what I've been given here.
    https://www.youtube.com/watch?v=15ez8mhJf0E






  2. #2
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    I use a cable tie. If it fits your done !

    If your rod bearing ends up allowing the rod to move over 0.030" then you will hear the bearing knock well before the rod hits the block.

  3. #3
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    And I've got only 18 thou clearance on this one.


  4. #4
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    How thick is your cable tie?

  5. #5
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    Quote Originally Posted by yellavk View Post
    And I've got only 18 thou clearance on this one.

    Think about how many cfm have to squeeze through that gap.

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    Yeah, very funny. Do COME racing generally aim for 50 to 60 thou clearance because they are stupid? How little clearance is generally considered acceptable?

    When this rotating assembly was first clearanced in a different block 7 years ago it turned over fine without interference by hand. Once the block heated up on the dyno and the revs went beyond a few thousand per minute a con rod bolt started knocking the block. I just don't fancy an episode of Déjà vu.
    Last edited by yellavk; 22-07-2017 at 06:46 PM.

  7. #7
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    If you understood it would be funny.

  8. #8
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    Quote Originally Posted by Actrol View Post
    If you understood it would be funny.

    So what, 60 thou versus 18 thou around that nut would give me 500mW more peak hp due to less windage?

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    Quote Originally Posted by yellavk View Post
    How thick is your cable tie?
    I would guess my cable tie is about 0.040" thick.

    0.018" is getting close, maybe unscrew that nut and linish a few thou off the point that is closest. You don't need to hack the whole thing, just the very top of the hex on that point.

    The engine warming up isn't enough to move more than a few thou, I would imagine the problem was in the side clearance between rods that caused the issue so wiggle each rod when you check the clearance to the block.

  10. #10
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    Yeah, that 30 thou one closes up several thou further when the rod is pushed over. The thing is that the clearance is pretty much identical on every single con rod nut. I don't get it. On each nut there is heaps of clearance on one side, as you can see in my photos, but it's close to touching on the other. Why would this be? It's almost as if the thing was dummied up when clearanced with a different set of rods that had a different bolt offset, if that is at all possible.

    And without pulling pistons out of bores it's very difficult to asses the amount of clearance underneath the camshaft tunnel, but I think that I can presume that they are the same. I'm currently immobile as a blind (was probably on her phone) woman in a 4WD wrote-off my only remaining transport just a couple of weeks after this 383 was pulled down. The plan was to get this thing in the car tomorrow, ready for the dyno next week. So much for that plan. And I paid to have this short motor assembled as I'm not set up at home or have the time to do this myself. Every_single_build. It's always the same deal. I'm so sick of this shit.

    Apologies for the rant.
    Last edited by yellavk; 22-07-2017 at 08:33 PM.

  11. #11
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    Can you speak to the assembler? I am sure all will agree that 0.040'' would be an acceptable minimum, & get his rationale? I understand your frustration. Good luck

  12. #12
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    Have you thought about taking it back to the guy and saying fix it? There will be marks on the rods and the block where they have been hitting, if you cant see the marks then it will be the inside bottom edges of the bores.
    Last edited by alffie; 23-07-2017 at 11:47 AM.

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    I do this on a SBC 383, I use a paper clip. Bend it so it follows the contour of the block. Its around 0.040". If it passes through it should be right. I crossed the line at 6900 rpm and all good.

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    Quote Originally Posted by yellavk View Post
    On each nut there is heaps of clearance on one side, as you can see in my photos, but it's close to touching on the other. Why would this be? It's almost as if the thing was dummied up when clearanced with a different set of rods that had a different bolt offset, if that is at all possible.
    Very possible.

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    I got in contact with the machine shop. The bloke who answers the phone agreed that 40 thou would be the minimum acceptable clearance. The block went back again and was returned to me with an average of only 24 thou minimum clearance on the con rod nuts (from the original 18). The shops machinist has different ideas to the guy who answers the phone. I was then given alternative nuts, which now give adequate clearance for the con rods.

    Now my only remaining concern is with the counterweight clearance. The front counterweight is the tightest, with only 8 thou of clearance at the closest point. Is this acceptable?




    Last edited by yellavk; 05-08-2017 at 03:49 PM.

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