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454 timing chain slipped a few teeht now no compression

This is a discussion on 454 timing chain slipped a few teeht now no compression within the Performance forums, part of the General Discussion category; is the 1990 454 ss engine a interfeince engine??? i ask becuase my brothers truck..hois chain slipped about 10 theeth ...

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    Curt 1992 chevy 5.7l
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    454 timing chain slipped a few teeht now no compression


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    is the 1990 454 ss engine a interfeince engine??? i ask becuase my brothers truck..hois chain slipped about 10 theeth or so..the gears loked bad...wellwe replaced the chain and gears...now no matter what we do we dcant get it to start it will jsut backfire through the intake....tried switching disty 180 no luck!....never had this probelm before as a last...idea we checked compression on number 1 and go zero....im lost..
    92 5.9l full roller,fully forged,scatt crank.AFR 190cc heads,Crane 2032cam,nv3500,S2 6 Puck clutch.Hurst Short Shifter,14-bolt,auburn 4.11.Carbed

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    Re: 454 timing chain slipped a few teeht now no compression

    Either cam timing is off, or a valve is bent or broken and hanging open. Have you pulled the valve covers and turned over the engine to see what is going on? What caused the timing chain and gears to fail? Its possible it dropped a valve...
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    Curt 1992 chevy 5.7l
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    Re: 454 timing chain slipped a few teeht now no compression

    ya pulled valve covers off ...all looks fine....all the rocckers move fine..no pushrods bent.....we se the cam dot to dot...12 and 6 o clock......made sure it was topdead center.... drop the disty back in and still no mater what we do it jsut pops big throught the intake...
    92 5.9l full roller,fully forged,scatt crank.AFR 190cc heads,Crane 2032cam,nv3500,S2 6 Puck clutch.Hurst Short Shifter,14-bolt,auburn 4.11.Carbed

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    Re: 454 timing chain slipped a few teeht now no compression

    Pull valve covers and valve spring hieght.Check compression.Probably made piston to valve contact.

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    Curt 1992 chevy 5.7l
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    Re: 454 timing chain slipped a few teeht now no compression

    i though the chevy 454 big blocks were non interference engines? am i wrong i thought even if the chain broke that the valves would not hit am i wrong
    92 5.9l full roller,fully forged,scatt crank.AFR 190cc heads,Crane 2032cam,nv3500,S2 6 Puck clutch.Hurst Short Shifter,14-bolt,auburn 4.11.Carbed

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    Re: 454 timing chain slipped a few teeht now no compression

    Pull valves covers and get back to us on what you see

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    Curt 1992 chevy 5.7l
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    Re: 454 timing chain slipped a few teeht now no compression

    i did all is fine all psuhrods are fine and wile crankling all valves go up and down fine...
    92 5.9l full roller,fully forged,scatt crank.AFR 190cc heads,Crane 2032cam,nv3500,S2 6 Puck clutch.Hurst Short Shifter,14-bolt,auburn 4.11.Carbed

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    Re: 454 timing chain slipped a few teeht now no compression

    dig deeper, you don't just 'lose timing gear teeth' and kill and engine every day.. something happened, and you gotta keep digging until you find it.

    at the very least, I'd pull the heads and take a look????
    yeah it's a lot of work, but doesn't seem like you're making progress
    with the little stuff so far?
    Last edited by para driver; 01-03-2010 at 07:57 PM.
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    Re: 454 timing chain slipped a few teeht now no compression

    Disconnect fuel pump relay.Do a compression test on all cylinders with the throttle blades open all the way.

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    Re: 454 timing chain slipped a few teeht now no compression

    Quote Originally Posted by 1500chevy5.7l View Post
    i though the chevy 454 big blocks were non interference engines? am i wrong i thought even if the chain broke that the valves would not hit am i wrong

    If the chain breaks on a BBC...it'll hang a couple valves open. It won't bend them all, but it will bend a couple.

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    Re: 454 timing chain slipped a few teeht now no compression

    Compression test will identify which ones

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    Curt 1992 chevy 5.7l
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    Re: 454 timing chain slipped a few teeht now no compression

    ok we got compression...still no start jsut a huge back fire through the i intake....no matter what i do i have used a dead stop and set the disty to 1..then set it 180...still nothing all it will do is backfir through the intake...
    92 5.9l full roller,fully forged,scatt crank.AFR 190cc heads,Crane 2032cam,nv3500,S2 6 Puck clutch.Hurst Short Shifter,14-bolt,auburn 4.11.Carbed

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    Re: 454 timing chain slipped a few teeht now no compression

    Back fire out the intake is an out of time probablem.Its a back fire and not compression through the intake right.Did you change the crank gear also.If not the key could of sheared causing the crank gear to be out of time.Also to install the #1 has to be tdc and also on compression stroke.Not just tdc.Set you distributor again with #1 at tdc and compression stroke.Disconnect fuel pump relay and crank it over alittle to clear the cylinders.Connect relay and try it again.Also make sure you getting spark to all cylinders.Oh how much compression did you get on the cylinders and were they pretty even.
    Last edited by 383TBI; 01-04-2010 at 10:21 AM.

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    Re: 454 timing chain slipped a few teeht now no compression

    You said earlier that you had the cam gear and crank gear marks at 6 and 12 o'clock. That will put your #1 piston at the top but not at TDC. Put the marks on both gears at 12 o'clock and I think you will be okay.

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    Re: 454 timing chain slipped a few teeht now no compression

    Right: "dot-to-dot" is #6 firing, not #1. It's the other instance of #1 TDC besides its firing, specifically the point at which the exh valve is closing and the int is opening as the #1 piston passes through TDC. One crank rev, and cam rev, away from #1 firing.

    Lift the dist, turn the shaft exactly 180, drop back in. Pretty easy fix. Then adjust the timing from there.

    Or, if it's already been twiddled with until you don't know where it is, find #1 firing by popping that plug out, and bump the starter gradually until you just start to get compression out the plug hole. Then turn the engine by hand to about 15 BTDC (about where the mark on the damper is aligned with the edge of the timing tab farther from the pass side of the car). Drop the dist in with the rotor pointed at about halfway between the #7 and #2 plug wire tower. Once it's all the way in, rotate the dist body until the star wheel teeth line up. Hook up the wires, reach in the window, and fire it up, then adjust the timing.

    BBCs are interference engines, on the intake side. I'm really surprised you didn't have bent push rods. Last time that happened to me, it broke 3 and bent the other 5. The push rods are so weak, they'll bend LONG before the valves will (stock PRs anyway); shouldn't be anything else damaged besides the PRs. Then they'll break after the motor has been running for a while from flexing at the bend.
    Last edited by RB04Av; 08-31-2010 at 04:49 PM.

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    Re: 454 timing chain slipped a few teeht now no compression

    I didn't realize that the 454's didn't have valve/piston clearance. Am about to take apart an early 70's 454 (in a boat) with a broken timing chain. So I will likely have intake valves bent??

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    Re: 454 timing chain slipped a few teeht now no compression

    Not necessarily... more likely, intake push rods, esp if they're the 5/16" ones.

    The motor I'm referring to above was an absolutely box-stock 74 454 in a full-size car. Stock cam, rubber rockers, everything.

 

 

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