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Summit racings engine kits, 400 sbc question

Discussion in 'The Garage' started by 55Willy, Jan 2, 2007.

?

what compression ration

Poll closed Jan 22, 2007.
  1. 9 to 1 ... like eating cheeto's

    5 vote(s)
    45.5%
  2. 9.6 to 1 almost naked

    2 vote(s)
    18.2%
  3. 10.5 to 1 naked in the bean bag chair with yellow fingers

    4 vote(s)
    36.4%
  1. 55Willy

    55Willy 3/4 ton status

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    I'm gonna be ordering my rebuild kit through them with thier federal mogul kits. I'm looking at them and I have 2 questions:

    1-
    why do the kits after 1976 not include pistons (mines a 78-79)

    2-
    what compression ration would you pick for a 6,000# suburban running 38-40's with a manual. also running hydro brakes so a big cam is not an issue.
     
  2. 55Willy

    55Willy 3/4 ton status

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    motor is a 400 with dart iron eagle heads with 72cc cambers. rollor rockers. gear drive timing kit. 670 truck avenger with a high rise open plane manifold.
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Depends on what octane fuel you want to run and also how big the camshaft is going to be. On average though for pump gas and still friendly without detonation keep the CR around 9:1, little higher if you run premium fuel and have a larger cam.
     
  4. 58 apache

    58 apache 1/2 ton status

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    im runnin a 9.78:1 compression have to use premium. buy a balanced assembly.and dont skimp on gaskets. use fel pro performance.i have a 516 525@50 cam with power brakes and an auto lose the holley and get an edelbrock if this is going to be a dd
     
  5. 58 apache

    58 apache 1/2 ton status

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  6. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Take this from personal experience....:wink1:

    Go 9.1:1. I have a 406ci with 9.2:1 compression and have to run premium fuel. If I needed to pull a trailer that was any kind of decent weight (4K+) I had to dump in a bottle of octane booster to keep it from pinging. Granted, I live in California and out of state gas is probably better, but not that much.

    400's love to ping, their cylinder temps are generally higher due to the lack of water jackets between the pistons, making them more vulnerable to detonation.

    I'd give up 5-10HP to be able to not have to worry about detonation, regardless you'll probably need premium anyway.
     
  7. 58 apache

    58 apache 1/2 ton status

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    anything under 93 octane and i have to use an additive. i orig had 54cc combustion heads 10.5:1 i HAD to swap heads to run decent on the street im pushin the limit now with 64cc chambers and 9.78:1....i also had to do ALOT of timing curve adjustment and vac adv adj. before i found an acceptable combo
     
  8. 55Willy

    55Willy 3/4 ton status

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    I'll have to look at the cam card, it's the comp cam 4x4 extreme, 270 ish.
     
  9. 55Willy

    55Willy 3/4 ton status

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    Location:
    Keizer, Or
    Brand:COMP Cams
    Product Line:COMP Cams Xtreme 4x4 Camshafts
    Cam Style:Hydraulic flat tappet
    Basic Operating RPM Range:1,800-6,000 RPM
    Intake Duration at 050 inch Lift:226
    Exhaust Duration at 050 inch Lift:234
    Duration at 050 inch Lift:226 int./234 exh.
    Advertised Intake Duration:270
    Advertised Exhaust Duration:278
    Advertised Duration:270 int./278 exh.
    Intake Valve Lift with Factory Rocker Arm Ratio:0.480 in.
    Exhaust Valve Lift with Factory Rocker Arm Ratio:0.498 in.
    Valve Lift with Factory Rocker Arm Ratio:0.480 int./0.498 exh.
    liftLobe Separation (degrees):111
    Intake Valve Lash:0.000 in.
    Exhaust Valve Lash:0.000 in.
    Computer Controlled Compatible:No
    Grind Number:CS X4 270H-11
     
  10. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    Sorry, but if you want more power go Holley. Holley carbs have crazy tuneability built into them. It may take some time and pacients to set it up right, but once you do, I promise you it will be worth the effort.

    I dd my truck with a Holley and I have no problems at all with it. Nor would I want another carb.
     
  11. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    I like Lunati Voodoo cams the best:

     
  12. kwissman

    kwissman 1/2 ton status

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    The Lunati VooDoo cams were designed by Harold Brookshire who used to own Ultradyne cams. They will make a little more power than the Comp extreme series and are easier on the valve train. The Comp extreme are hard on valve train since they close the valve quick.
     

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