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  1. #1
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    Cool 253 v8 interference

    Does the standard 253 v8 have clearance between the valves and pistons if the timing is out ie broken timing chain. valve is down when piston at tdc . replaced timing chain and sprockets motor turns over but wont start .?

  2. #2
    Do you ever leave? HQ308Ute's Avatar
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    if the chain breaks the cam wont turn so the valves stay closed.. check all your timing again.

  3. #3
    been here .......too long Smitty2's Avatar
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    Quote Originally Posted by HQ308Ute View Post
    if the chain breaks the cam wont turn so the valves stay closed.. check all your timing again.
    ummm.. not quite right I think

    those valves closed will stay closed but those open (ie that lifter is on the cam nose)
    will stay open (as the cam is not turning)

    those open valves can be hit by a piston at TDC
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  4. #4
    Do you ever leave? HQ308Ute's Avatar
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    Quote Originally Posted by Smitty2 View Post
    ummm.. not quite right I think

    those valves closed will stay closed but those open (ie that lifter is on the cam nose)
    will stay open (as the cam is not turning)

    those open valves can be hit by a piston at TDC
    ok.. i figure the springs close the valves. having said that i'm not completely sure if its possible, ive broken two chains in my life and didnt hurt the valves... see if the harmonic balancer has shifted as well.

    Hmm, maybe if you're revving the clappers out of it??
    Last edited by HQ308Ute; 17-10-2018 at 08:38 AM.

  5. #5
    casual poster Blackman's Avatar
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    Quote Originally Posted by HQ308Ute View Post
    if the chain breaks the cam wont turn so the valves stay closed.. check all your timing again.
    Hummmmm. If the chain breaks you will still have some valves open out of the 16

  6. #6
    Do you ever leave? HQ308Ute's Avatar
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    Quote Originally Posted by Blackman View Post
    Hummmmm. If the chain breaks you will still have some valves open out of the 16
    there you go answered you need the heads rebuilt

  7. #7
    casual poster Blackman's Avatar
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    Quote Originally Posted by HQ308Ute View Post
    there you go answered you need the heads rebuilt
    I would say depending on what lift your cam has if the chain breaks it will bend some valves (maybe 3 to 4) and possible damage two or more pistons. eeek!!

  8. #8
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    Do a leak down test. Another easy way to check for bent valves is to pull the plugs and put your finger over the plug hole of each cylinder (one at a time) while a mate turns the engine over - you should feel the compression as the motor is turned over.

  9. #9
    Do you ever leave? HQ308Ute's Avatar
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    its a lesson learned anyway, dont let the cam chain get too sloppy on holden 5 litre..

  10. #10
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    Pretty sure a standard 253 is a free spinning engine.

  11. #11
    Do you ever leave? EH179's Avatar
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    If the valve is down at tdc on that cylinder, you have the cam timing wrong.

  12. #12
    Do you ever leave? EH179's Avatar
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    Quote Originally Posted by HQ 368 View Post
    Pretty sure a standard 253 is a free spinning engine.

  13. #13
    Do you ever leave? HQ308Ute's Avatar
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    Quote Originally Posted by HQ 368 View Post
    Pretty sure a standard 253 is a free spinning engine.
    lol that's what a couple of mechanics have told me actually, that the Holden v8 is a non interference motor.

  14. #14
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    Apparently after around .460 valve lift valves can touch pistons assuming a mostly standard red motor.

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    Quote Originally Posted by cbw_09 View Post
    Apparently after around .460” valve lift valves can touch pistons assuming a mostly standard red motor.
    Thank you everyone I did a compression test and found all 8 cylinders hold good compression. A engine builder has mentioned the lifters could bleed down if oil pressure is low. He suggested to prime the oil pump and check oil presssure low pressure wont pump up the lifters enough to open the valves properly. This can be a problem with older 253 engines he suggests

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