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'93 chevy C1500 350 timing chain install.... scratching head on this one

This is a discussion on '93 chevy C1500 350 timing chain install.... scratching head on this one within the Technical / Maintenance forums, part of the General Discussion category; I need some insite on this one. I've built many 350's in the 80's where you always put #1 piston ...

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    '93 chevy C1500 350 timing chain install.... scratching head on this one


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    I need some insite on this one. I've built many 350's in the 80's where you always put #1 piston at TDC, align the dots together on the timing gears, put on the chain and you're done... almost...

    My son has a'93 Chevy c1500 with a tbi 350. Before i took off the stock timing chain and gears, i put the #1 piston on the compression stroke at tdc, the balancer was at zero on the timing tab, pulled off the balancer and timing cover and the dots on the timing gears weren't together. Cam gear dot was at 12 o'clock..

    The Chilton manual says when installing a new timing gear set to first put the #1 piston at tdc on the compression stroke, then crank the motor over 360 degrees and install the timing gears with the dots together. ... I read it 5 times to see if i was missing something... nothing missed...

    Is this a typo? The motor ran fine before... The firing order on the '93 is the same as the old motors... What gives???

    Anyone else heard of this? I haven't fired it up yet or tried to as I'm not finished putting it all back together.

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Sounds like your not on the number one compression stroke. Cams 180 out

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Dots together is at #6, dots at 12 oclock is #1
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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    is it possible that the cam gear has two dots?[IMG][/IMG] otherwise my info says dot to dot. EDIT: instructions from manual;Remove or Disconnect



    Remove engine front cover. Refer to Timing Cover. See: Timing Cover\Service and Repair
    Crank the engine until the marks punched on crankshaft sprocket (59) and camshaft sprocket (101) line up with shaft centers.
    Remove bolts attaching the camshaft sprocket (101) to the camshaft.
    Remove timing chain (58) with the camshaft sprocket (101). CAUTION: This is an interference engine. Do not turn the crankshaft after the timing chain and camshaft sprocket have been removed to prevent damage to engine parts
    Last edited by 94-2500; 01-22-2010 at 06:42 PM.

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    My dad and I went round and round about this two weeks ago. This is the definitive answer. When you install the timing gears dot to dot, the number one cylinder will be at tdc, but cylinder number six will be firing. All that means is that you need to roll the motor over one turn before stabbing the dizzy. My dad has always installed the timing gears on small chevy's with the crank dot and the cam dot both at twelve o' clock, which puts number one cylinder at the correct spot to stab the dizzy w/out having to turn the motor over one revolution. It is six of one, half a dozen of the other. In my opinion, install the timing gears dot to dot, and roll the motor over one revolution. At that point the timing gears will both be at twelve o' clock and you can install the dizzy to fire the number one cylinder. I hope that made some sense.

    -Jared

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Then why was it put together that way from the factory using #6 instead of #1? This motor has never been apart. It's weird.. The manual goes into great detail with pics showing the cam out 180.

    No the cam gear only has 1 dot(punch).

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Quote Originally Posted by 94-2500 View Post
    is it possible that the cam gear has two dots?[IMG][/IMG] otherwise my info says dot to dot. EDIT: instructions from manual;Remove or Disconnect



    Remove engine front cover. Refer to Timing Cover. See: Timing Cover\Service and Repair
    Crank the engine until the marks punched on crankshaft sprocket (59) and camshaft sprocket (101) line up with shaft centers.
    Remove bolts attaching the camshaft sprocket (101) to the camshaft.
    Remove timing chain (58) with the camshaft sprocket (101). CAUTION: This is an interference engine. Do not turn the crankshaft after the timing chain and camshaft sprocket have been removed to prevent damage to engine parts
    Your pic shows exactly what the book says on how to install it which to me would normally be 180 out. Normally the index pin on the cam should be at 3 o'clock not 9 o'clock. The weird thing is the motot is all stock, never been apart and it came out this way and ran fine.

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Quote Originally Posted by chevydurmax4x4 View Post
    Then why was it put together that way from the factory using #6 instead of #1?
    This is what my dad and I were arguing about. First of all, assume this. When have you ever put an engine together without rotating the crankshaft at some point? In any engine build, one inevitably spins the crank a few times, and then just rolls it up to #1 to stab the dizzy. So does it matter that the timing gears are keyed to be set up with number 6 firing? It doesn't matter that the engine has never been apart. I don't know why the factory wouldn't just set the timing dots up at number one firing. I do know that what I wrote in the previous post is absolutely inarguable. The timing marks are supposed to be dot to dot. That will in theory get the cam phasing where it should be. All you need to know is that BEFORE you install the distributor, you NEED to roll the #1 piston to tdc on the compression stroke. I can't explain it any better than that. All sbc timing sets are designed to be set up dot to dot. All sbc timing sets will, at that alignment, be firing on number 6. The cam phasing is not 180 out, period. Turn the crank one revolution and stab the dizzy. End of story.

    -Jared
    Last edited by Baitshop; 01-23-2010 at 07:04 AM.

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Jared,
    Okay. I've run into the same problem as above. However, the problem I had is how do you know when you've reached 360 degrees? There is no mark on the balancer. I spun it until the #1 piston was at TDC and the timing mark was on zero degrees, but that is how I had it before and the truck wouldn't start.

    PS. WHen I put the timing chain on dot to dot (cam dot at 6 oclock, crank dot at 12 oclock) the #1 piston is NOT at TDC.
    Last edited by akoutdoors; 06-29-2010 at 02:53 PM.

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Quote Originally Posted by akoutdoors View Post
    Jared,
    Okay. I've run into the same problem as above. However, the problem I had is how do you know when you've reached 360 degrees? There is no mark on the balancer. I spun it until the #1 piston was at TDC and the timing mark was on zero degrees, but that is how I had it before and the truck wouldn't start.

    PS. WHen I put the timing chain on dot to dot (cam dot at 6 oclock, crank dot at 12 oclock) the #1 piston is NOT at TDC.
    Do you have heads installed? you can tell by rocker arm movement.


    Why wasn't it at TDC when you installed the chain?

    That is probably why it will not start.
    Quote Originally Posted by Xander Berkeley
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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    No, It wasn't at TDC . Yes, the heads are installed. I'm verifying #1 TDC by watching the rocker arms (valve covers are off) and by placing a wire in the spark plug hole to make sure. So what do I do now? If the timing gears are dot to dot then I'm not worried about them being in sync, but how do I set the distributor correctly?

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    To my understanding, having the engine at #1 TDC should not matter when taking the engine apart. The cam and crank aren't going to cause any problems as long as the dots are together when reinstalled . The problem is, now that I have the timing chain back on with the dots together how do I position the engine so I can reinstall the distributor?

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    It is probably a tooth off. It will not start or hiccup if you advance or retard the dizzy at all by hand?
    Last edited by XLR8N; 06-29-2010 at 03:32 PM.
    Quote Originally Posted by Xander Berkeley
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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    use a straightedge and make sure all the centers and dots line up . The key on the crank points up at # 1 cylinder . The factory says the dots @ 12:00 but it doesn't matter . put the dots together and use a straightedge to make sure everything is centered . then adjust the valves . Once the valves are adjusted turn the motor over with your finger over #1 spark plug hole . When the compression pops your finger off you know you're @ #1 firing . Then stab the dizzy with your timing mark @ 0 degrees . Pretty much foolproof . If you don't use a straightedge it's really easy to miss by 1 tooth .
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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Thanks for the suggestions guys. I just posted a full description of the problem on a new thread.
    As far as the dist being a tooth off, I tried retarding the timing to no avail. THe rotor on the dizzy is pointed exactly at #1 cylinder with the balancer mark at 0 degrees.
    As far as the timing marks go, those little buggers are pretty straight.

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    Re: '93 chevy C1500 350 timing chain install.... scratching head on this one

    Curious, by trying to advance or retard the dizzy what we're doing is compensating for it being a tooth off, right?

 

 

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