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chevy 327 dirt track,late body,17 inch of vacuum rule,

Discussion in 'COMP Cams Support Forum' started by fridge, Jan 21, 2016.

  1. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    what is the best cam for a 327,1968,stock flat top,stock 64 cc heads,
    whit the most torque and H.P over 17 inch of vacuum ?
     
  2. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    Does it need to be a hydraulic flat tappet? Or can it be solid?
     
  3. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    it can be solid
     
  4. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    is the L-79 cam good for this application,will it have 17 inch of vacuum
     
  5. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    The L79 cam should do the job, but we can do better with an Xtreme Energy series camshaft. I would suggest our cam part# 12-268-4, which has a wider lobe separation angle to make good vacuum. It shouldn't have any trouble making 17" as low as 800rpm.
     
    fridge likes this.
  6. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    Thanks !!!im going to give it a try !!!
     
  7. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    Hi ,
    i have another question,
    will this cam work with 980 valve spring and stock retainer and stock heads,
    i have a 230 lbs open valve spring rule,
    its going to have 1.700 install height
    i thinks it will be fine but just want to make sure!
     
  8. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    Man, I hate spring pressure rules like that! It honestly leads to more broken parts.
    Trying to use the lightest possible parts is the key.
    I doubt titanium retainers are legal, but is tool steel?
     
  9. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    it s got to be original,those tool steel, do they look like original ??
    i have never seen them test somebody spring, what if i use 981
    are those ok?
     
  10. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    Tool steel are pretty shiny, not black, but a magnet does stick to them.
    I like the 981 spring a lot better.
     
  11. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    my cam is ordered,
    can you tell me about a much compression this engine is going to have approx ?
    .040 head gasket compress tickles.
    its a brand new engine with .040 oversize flat top piston.
     
  12. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    How far is the piston down from the deck at TDC?
    Does the piston have 4 "eyebrow" reliefs? Or just two?

    If the engine is zero decked with a 4 eyebrow flat top piston, you would be at 9.82:1 compression.

    If the piston is down in the bore .010" at TDC, then that makes your compressoin 9.59:1.
     
  13. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    its at original deck height, 4 eyebrow
    whats the normal gm piston height ,is it .020 ?
     
  14. maxwell

    maxwell Moderator Staff Member

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    Jul 5, 2012
    I have seen as much as .032. Can't really say until you check it.
     
  15. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    ok whit 9.82:1 is 94 octane gas going to be ok
    and at what would you set your engine timing at wot or total timing ?
    thanks in advanced Matt
    really helpful !!!
     
  16. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    I think that is plenty of octane for that compression. I would start out at 32 degrees total to shake the car down, then bump it up a little at a time and see where it runs the best.
    My guess is 34-35 will make the most power.
     
  17. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    hi Max,
    can i use 981-16 or 980-16 valve spring with my stock gm retainer ?
    thanks again
     
  18. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    They should fit the factory retainer fine. Since it is a race application, it would be worth investment to get a good set of retainers and valve locks. Unless it is against the rules...
     
  19. fridge

    fridge New Member

    Joined:
    Jan 21, 2016
    Hi Max,
    the engine is at the machine shop,
    what kind of h.p and torque should i have with this set-up approx ??
     
  20. maxwell

    maxwell Moderator Staff Member

    Joined:
    Jul 5, 2012
    Well, that's the $64,000 question! A dyno is the only way to know for sure.

    I would expect the Xtreme cam to be worth about 10-20hp over the L79 cam.
     

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