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  1. #1
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    1995 Mariah 212Z 355
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    Sep 2011
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    Tune Up and Timing

    Went out on the water today after doing tune up including Cap Mallory, Rotor Mallory, wires 8mm Mallory, plugs AC Delco. When I started the engine at the ramp, had a tough time to idle which had nothing to do with idle speed screw adjustment. No misfire under load but had big loss in power at WOT.

    Checked all wires from cap to plugs and was correct. Had a feeling the timing was retarded a little. Did not have my timing light but just advanced the Distributor a little until the idle speed was at a normal speed. Usually time to 30 BTDC but will have to dial in timing next time. Anyway the power was restored with the advance and ran smooth from idle to WOT.

    I timed the motor two months ago and ran great at WOT but was a little rough at low RPM which is why I did the tune up.

    My question is how did the timing become retarded just by changing the plugs, wires, cap and rotor? I guess the full tune up requires a recheck with the timing light.

    Now the motor runs the best it ever has just need to fine tune the timing back to 30.

    I was just surprised that those few changes required an advance of the timing?

    Any ideas as to why the timing needed readjustment?

    Thanks

  2. #2
    Platinum Member Platinum Member mike tkach's Avatar
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    you might of not put no 1 wire in the same place on the cap,if you moved it 1 socket over,timing would be way off,what are you running your total timing at,if it is 30,its a little low imo.
    MIKE TKACH

  3. #3
    Charter Member # 55 Charter Member Griff's Avatar
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    Because the distributor probably moved a little when you did the tune up.

  4. #4
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    1995 Mariah 212Z 355
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    30 degree timing

    Quote Originally Posted by mike tkach View Post
    you might of not put no 1 wire in the same place on the cap,if you moved it 1 socket over,timing would be way off,what are you running your total timing at,if it is 30,its a little low imo.
    Mike,

    I am running Vortec cast iron heads and was advised to stay safe with 30 total timing at 3000rpm.

    Thanks

  5. #5
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    1995 Mariah 212Z 355
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    Moved Distributor

    Quote Originally Posted by Griff View Post
    Because the distributor probably moved a little when you did the tune up.
    Griff,

    Before I started the tune up I made sure the distrib hold down was tight. Just to note when i changed the plugs, number 8 plug was a little rich with wet fuel and number 5 had more carbon build up then the rest. Possible bad plug or wire?

    Thanks

  6. #6
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    May 2010
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    636
    Quote Originally Posted by Mariah212Z View Post
    Mike,

    I am running Vortec cast iron heads and was advised to stay safe with 30 total timing at 3000rpm.

    Thanks
    I think he is right even wit cast iron heads you can run as much as 34. What kind of gas do you run? Even 32 would be better and I can't imagine any problems

  7. #7
    VIP Member VIP Member MILD THUNDER's Avatar
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    Timing wont change unless you moved the distributor. Or like Mike said, you are off on the firing order on the cap. Like if you removed all the plug wires, and started #1 where #8 was, and continued that order. That would do it. Adjusting the distributor with the timing light hooked up will solve that issue.

    I'd double check the timing spec at full advance. 30* seems low even with the vortec heads. I would think at least 32*.

  8. #8
    Platinum Member Platinum Member mike tkach's Avatar
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    with the timing set at 30,the egt,s will be hot,i would run no less than 32,i think 33 is where i would go,at 30,its tough on the exhaust valves&seats.
    MIKE TKACH

  9. #9
    Charter Member # 55 Charter Member Griff's Avatar
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    SBC vortec heads do not like much timing. 30* is about max for them.

  10. #10
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    1998 Velocity 280
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    Oct 2010
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    Cheboygan, MI
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    Vortec heads are small chamber and have a fast burn and only require 28-30 degrees depending on compresion. BBC with there large chamber burn slower and require more timing.


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