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Thread: New 409 Sbc Chassis Dyno
          
   
   

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  1. #1
    chevymans409's Avatar
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    New 409 Sbc Chassis Dyno

     



    So I have a 68 camaro 409 sbc w/ M21 Four speed, hooker side pipe headers w/ high flow inserts.


    400 sbc bored 40 W/ splayed main caps
    scat crank
    h-beam 6" rods
    SRP flat top piston
    rev kit
    comp roller lifters vertical looking bar
    comp 1.5 roller rockers
    AFR 210 comp heads
    super victor manifold
    Quick fuel p-950 carb
    501C2LUN Solid roller cam Deg *7 adv
    6al Msd


    So I went to the chassis dyno the other day and made three dyno pulls changing full advance each time.

    1) 403 RWHP at 5300 and 424 RWTQ @ 35* full timing by 2800
    2) 399 RWHP at 5300 and 428 RWTQ @ 31* full timing by 2800
    3) 405 RWHP at 5300 and 434 RWTQ @ 36* full timing by 2800

    The Air fuel ratio is between 12 and 13 threw the pulls. I also have a 1 inch spacer and 1/2 NOS plate. (The bottle is not in the car but its set for it). Compression is 11.4- 1 i run 92 octange.


    The cam the heads and the intake are all suppose to make power between 3500 - 7500 so why is my max power 5200-5400 and it falls off prety good by 7000. So what im asking I guess ….. what is it that moves the peak HP up the rpm scale?

  2. #2
    suprstock's Avatar
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    advancing the cam moves peak hp down in rpm range retarding cam moves peak hp up in rpm range.
    302 c.i. of knowledge power

  3. #3
    jerry clayton's Avatar
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    was timing the only thing you changed?

  4. #4
    chevymans409's Avatar
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    Yea timing is the only thing that i changed at the dyno started 35 then 31 ended at 36.

    The only thing i have changed sence the dyno was the valve lash i had it at .16 cold i changed it to .22 hot.

  5. #5
    jerry clayton's Avatar
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    If you want to move the numbers up---retard the cam setting to straight up and see where it goes--might want to check for ex valve clearance at 10* btdc

  6. #6
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    Quote Originally Posted by jerry clayton View Post
    If you want to move the numbers up---retard the cam setting to straight up and see where it goes--might want to check for ex valve clearance at 10* btdc
    NOW im confused.....For years i always advance as much as possible for max top end hp even my three dyno pulls shows the same when i retanded from 35 to 31 i lost 4 hp then up to 36 i gained 6,the hole time peak hp was around 5300 rpm's.

  7. #7
    jerry clayton's Avatar
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    You are confused between ignition timing and camshaft timing----advancing the cam (7*) will bring the power band lower---retard the cam to straight up and the numbers will be at a higher number--however you need to check that you have exhaust valve clearance as the piston is chasing the valve as it closes and the closet is area from arond 10*btdc to about tdc

  8. #8
    chevymans409's Avatar
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    Oh i see...ya..

    cam deg is nothing i have ever done..... I had some one help me with that well good thing i put in a timing cover has an easy acsess to ajust cam timing... I have to pull the hole top down to check vaule clearance.

  9. #9
    suprstock's Avatar
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    you can put checker springs on 1 in.and 1 ex and check valve clearance that way. if its a street car just live with it the way it is .prolly still do a smoke show.
    302 c.i. of knowledge power

  10. #10
    jerry clayton's Avatar
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    If you are retarding the cam you will only need to check exhaust because intake clearance will increase as the cam is retarded---of course knowing what the clearance is makes it nice to know when playing with the cam timing--

  11. #11
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    Thanks alot im going to set to straight up and go from there.

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