Crank clearance

Discussion in 'Troubleshooting & Diagnosis' started by Dennis Wilkie, Nov 29, 2020.

  1. Dennis Wilkie

    Dennis Wilkie Veteran Member

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    I've got a question about the crank clearance in my block. I'm putting in a new crankshaft and I just noticed this. Is this normal, or does it look like it was done by the crankshaft itself?
     
  2. Chevyforever

    Chevyforever Veteran Member

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    Is it an aftermarket crank or a 383 stroker build ?.
     
    Last edited: Dec 2, 2020
  3. Dennis Wilkie

    Dennis Wilkie Veteran Member

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    It's a standard size Scat 9-10526 that's going in it, and I just got it back from getting balanced last week. It was the OEM that came out. I ran across a couple of pics that all referenced stroker setups with similar markings, but nothing as far as factory goes. That's why I was curious and wanting to get some opinions and outside input. The main bearings were in terrible condition, and the harmonic balancer had started to separate. So I figured both of those probably had an something to do with it. As soon as I pulled 1 main cap off, I knew nothing good was gonna follow
     

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  4. Chevyforever

    Chevyforever Veteran Member

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    I thought the video was your discovery after installing new crank.
     
  5. Ihada70Z28B4

    Ihada70Z28B4 Veteran Member

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    If the crank did that it had to be audible.
     
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  6. Dennis Wilkie

    Dennis Wilkie Veteran Member

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    Naw, I just saw that last night, and was trying to get some insight before I throw $1000 worth of new parts in the block. If it was audible, it was before I bought it. True dual, no cats/no baffle Magnaflow exhaust makes it hard to hear anything, lol. But I definitely never heard anything that would've made those kinds marks. The only thing i've ever heard from the engine was related to these notoriously loud zz4 heads. Everything aside from the intake, heads, lifters, cam, and pushrods, were all original, including every one of the bearings. I've replaced everything with new parts since I acquired it in January of 2018. This crank is the last thing to replace because it was the most expensive. The pistons and rods are also brand new. They're actually the only parts internally that have any miles, and they're right at 1000. Now i'm about to try and bring it all together at once, and hope for the best. I thought the old crank counterweights looked pretty f'd up, but i've never dealt with one before this...and I hope I never have to again, lol.
     
  7. sandlapper

    sandlapper Veteran Member

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    clearly, that crank is an OE GM cast piece for 1 pc rms. Don't see any witness marks on counterweights but you strategically positioned it in pic so we can't see diddly.

    That one bearing shell you show is pooched But not bad enough to permit counterweights to reach block.

    I'm Not asking simply to beat you up; I'm trying to diagnose.

    What is casting number of block?

    What are the proximate causes of damages to journals & shells ?

    Is motor in car?
    Did you drop crank with pistons in bores? If so, why?

    Is or Was this an OE ZZ4 motor when new?
    Or an assemblage of bits from more than one motor?
    Were both block & crank married when New ?
     
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  8. sandlapper

    sandlapper Veteran Member

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    shot in the dark, pig in a poke, wth, double-WAG
    ? is that one of the unique OE GM blocks specific to their HT383 & its kin?
    Instead of 3.750 stroke, those motors have a 4.000-4.005 bore with 3.800 stroke to make 383" and blocks are specially clearanced-machined for that 3.8" and have their own part number; distinct from 350 blocks' pn. However, they share same casting number with 350 blocks.

    -add-
    fwiw, the OE GM 383 3.8" crank is a Forged steel piece
     
    Last edited: Nov 30, 2020
  9. Dennis Wilkie

    Dennis Wilkie Veteran Member

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    It's a 638 block, and it's sitting on a stand right now with the pistons back in it. The crank casting is 14088526, and it's sitting exactly where I put it when I took it out, and the people who swapped the motor before I got the truck, threw a cam in it, without changing anything else. I'm honestly not surprised by anything at this point, because i've seen just about every half-assed thing imaginable done to this truck. The rods and pistons I put in are the exact same size as what came out. (4.000 bore and 3.48 stroke) All of the bearings were the original factory bearings on the crank, cam, and rods. The harmonic balancer was starting to separate from the rubber and the bearings all looked like they almost served no purpose anymore. I've got 100% all brand new parts and bearings ready to go back in it as soon as my gasket set gets here. I'm also going to replace all of the valve seals while the heads are off. The new parts aren't going to be an issue...I'm trying to figure out how much damage these tweakers did to the block before I put all of this money in it. I can take as many pictures as you want of whatever you want to see. Ask and ye shall receive
     

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  10. sandlapper

    sandlapper Veteran Member

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    I'd already blown up first pic of crank to see its casting number.
    *show us the outmost radii of ALL of crank's counterweights; looking at crank for evidence of contact with block.

    seems this is a truck and you really don't/can't Know history of motor as well as its block origin.

    And on second thought, afaik all OE GM 383 motors have 4-bolt mains while it seems your block has 2-bolt mains.
     

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