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Thread: should I be worried? rebuilt motor burning oil

  1. #21
    VCVC Member Dan Wilson's Avatar
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    Thanks for the useful info, I appreciate it. Just to clarify, the pictures shown are my old factory built engine, not the one in question.




    Quote Originally Posted by fustkarr View Post
    If your running moly rings you can expect elevated oil usage for approx 2000. Miles.if the rebuilder used something else it could take as long as 10k. GM uses a cast iron that's pretty soft (low tin)...wears faster than say Toyota blocks but breaks in faster. For break in you should be using a high solpher? Oil or additive. A lot of acceleration and slowing down using the engine as a brake (loads the rings against the cyp.walls.) willaid the break-in. Frequent oil/filter changes will rid the motor of trash that gets shook loose.Long periods of idleing are not recommended. Never disassembled a i6 but based on your flics your seals could have just disintegrated w/old age. The bronze parts your looking for are replacement valve guides. As a engine racks up miles the cask iron head "guides" (holes that the valve pokes thru) experience wear which leads to leakage, allowing oil to migrate past the valve/seal. To restore the fit, the holes are drilled oversize and a bronze guide is pressed in.I think its possible that stock I6s came w/o seals. My guess would be that a engine that required a rering had enough miles to require a valve job/bronze guides and seals that would fit over the valve stem and over the cast iron valve boss.The fact that yours doesn't have the seals suggest this was a backyard down n dirty job...or at least warrants further looksee.BTW, valves run around .0003 inch clearance .
    Gluk,Randy

  2. #22
    VCVC Member Dan Wilson's Avatar
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    In defense of my own eyes I did a pretty close inspection of the engine and nothing stood out as a rattle can rebuild. That said, probably best to wait it out put some miles on it before I get too worried. I did learn one thing, it's easy to take valve springs off while the head is off but I would be sweating it if I attempt it on the engine lol.

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    VCVC Charter Member Vanner68's Avatar
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    A telltale is whether or not there is crosshatch in the cylinders.

    If the block has had any machine work done, usually the cylinders get honed. A backyard builder generally does not do this, and the rings will take longer to seal, if at all.
    Gregg Groff


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    1968 Chevy G20 108 panel Now with 454 power!

    1965 Chevy G10 panel- OHC Pontiac inline 6

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    Maybe...maybe, you can rent/borrow a mini camera, remove a sparkplug and take a look inside to see whats goinon. Possibly a builders supply might have them to rent out, or u could buy one {about 150/200}...enough resolution to see crosshatch?
    Gluk, Randy

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    VCVC Charter Member Vanner68's Avatar
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    Gregg Groff


    There's no place like 127.0.0.1

    1968 Chevy G20 108 panel Now with 454 power!

    1965 Chevy G10 panel- OHC Pontiac inline 6

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    If you have a indicator and a mag base you can get an idea of whats going on w/the valves/guides by placing the indicator against the valve stem and pressing w/your thumb....003/4 slop means that head wasn't touched {w/springs etc. removed}..W/that same indicator you can place it against the crank bolt and move the crank back/forth and check the end play...too much play means the bearings probably wern't replaced. BTW, all motors look the same from the outside, thats why compression testers/leak down testers & indicators are required. Unless your buying from a trusted source, consider any purchase a gamble or buy w/the express intent of rebuilding.
    Gluk, Randy

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    VCVC Member Dan Wilson's Avatar
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    Thumbs up

    Cool tool!, I can also save on my next colonoscopy. Probably TMI.

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    VCVC Member TurboVan's Avatar
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    I've been thru this with Taco. Only the rubber umbrella-type seals will fit between the springs and those fat original (cast iron) guides.
    If you want something better, like teflon seals (I have no idea what he meant by "brass seals", there is no such thing), you have to have the guides' outside machined smaller so they can press on.
    If the guides are badly worn, or if you want to go whole hog, you can spring for bronzewall guides, that go inside the guides (expensive), they transfer heat better preventing burned valves, and they wear more slowly than iron guides.
    Last edited by TurboVan; 10-02-2015 at 01:16 AM.
    Keep one foot in the gutter, one fist in the gold...

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