hls3073z

valve timing advanced - not good for low end?

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    Way back almost before I can remember in my stupider days I took my 73 z with 40K miles  to the local expert/racer  to check valve clearances.    I asked him to advance that timing gear a notch as I thought that the chain may have stretched.  I think all that did was shift the power curve further up in the rpm range  and contributed to my feeling like the car does not have enough low end torque?

    Then I added the larger  motosport tubo exhaust pipe.  Made the problem even worse? 

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    I thought that closing the valves sooner moved the power peaks to lower RPM.  Which is what happens if you move to the 2 or 3 hole.  There's a method for checking valve timing.  The notch and groove, shown in the Engine Mechanical chapter if you want to check yours.

    Your exhaust pipe wouldn't have much effect on power peaks.

     

    Found a good reference - http://www.compcams.com/Pages/413/cam-timing-lobe-separation-angle.aspx

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    I put mine on #3 right off the bat after rebuilding the motor.  It has tons of low end but peters out around 6,000RPM.  I too went with the local 'experts" advice but now I'm sick of it and will be going back to at least #2 but most likely #1.

    All I do is shift gears, constantly. :cry:

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    There are some things to consider . Most cam grinds of performance cams already put some advance into the grind itself. 

    Head shaving and chain stretch . If you had a straight head and didn’t have to shave a bunch to get it it right , or you chain is new , advancing the cam timing might not get expected results.

    Example for me was that my head and block were shaved around .050 total and no shims , so advancing cam 8 degrees was really needed. 

    Cliffs experience sounds about right for advancing timing , more power low end. 

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    I don't mind shifting gears.  My complaint was that unless I reved up and slipped the clutch there was a stumble on takeoff.  Now...I am really spoiled as I have a duramax 3/4T diesel truck  and it just leaps right at the start and shifts 6 gears faster than I could ever think about it.  The z engine is total stock except I put a 280zx distributor and ignition on it.

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    I’d say you have a tuning issue. Though gearing helps the smaller 2.4 , there should be no stumble and still should be able to take off in 2nd gear if need be. 

    I would recheck timing (ignition) . I’d also make sure cam timing was done correctly . Everything including fuel should be checked . Something doesn’t seem right 

     

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    7 hours ago, siteunseen said:

    I put mine on #3 right off the bat after rebuilding the motor.  It has tons of low end but peters out around 6,000RPM.  I too went with the local 'experts" advice but now I'm sick of it and will be going back to at least #2 but most likely #1.

    All I do is shift gears, constantly. :cry:

    @LeonV

    I deserve a big "I TOLD YOU SO!" so I'm getting in front of it.

    I'm hard headed but I do learn from my mistakes.

    So thank you! 

    Edited by siteunseen

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