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Automotive Heads are tested need cam help (classic sbc)

  1. Jun 8, 2012 #1
    195cc intake runner, 64cc combustion chamber, aluminum, 2.02, and 1.60 valves
    Superflow sf 600 flow com
    air speed: 380-400FT, 375-410SC



    2500lb car 245/50r16 street tires rated at 320aa by firestone (I don't really need tq the car is very light and I am limited on tire)
    1987 700r4 trans
    3.545 rear gear ratio
    10.25:1 compression
    chev 327 40 over now may end up 60 over soon
    1.6:1 rocker ratio

    Looking for a solid flat tappet.

    I'm looking to have a very WIDE rpm range, as much as possible. Comp claims the old duntov 30-30 is between 2300-6900. I'm talking that kind of wide. The issue with that cam is that the one they sell it for a 350, in a 327 that would bump my rpm past what I want it to be. The 30-30 does suck (compared to modern cam profiles), I am just pointing out that a wide powerband in a solid flat tappet can be done. Also when I was saying the difference between a 350 and a 327. The small crank throw will up the rpm a bit. Instead of being at 2300 it would be like 2500-2600, and instead of being 6900 it would be like 7200-7300. That is too peaky for me. 2300 to 6900 would be perfect if it was rated for the 327. When comp rates those numbers they are all done with a 350 base. Not a 3.25 but a 3.48 crank.

    I'm looking for a 6700-7000 peak rpm, with it coming in as low as I can get it at.

    One thing I have heard and read a lot of debate about is the fact that the 327 doesn't sit at top dead center for very long so a wide lsa (about a 112-114) would be beneficial. Also it would kill the tq down low. The other end of this opinion is that one could do a 110 lsa and advance it quite a bit. I don't honestly know what would be best. Some help/thoughts/advice would be great.

    The car is intended for the road course at BIR in MN. Both the outer longer track and shorter center track.

    It looks like 1st gear is just to get going and 2nd gear should be about 33 mph at 2500 rpm and will be 80mph at 6000rpm. 3rd will go from 55mph @ 2500rpm to 130 @ 6000rpm or 140 @ 6500 rpm so 3rd should be a great gear for most of the high speed sections. 2nd should be enough for any tight stuff. Overdrive is 200mph + so that's good for a bit of extra pull down a straight if I'm able to go faster than 140mph before braking for the turn.

    Looking at the Brainerd track it looks like a lot of high speed corners and long straightaways without too many tight corners. I have wide gearing so this should suit the track well but it means I need a wide powerband as well.

    Help and advise or a point in the right direction would be great.
    Last edited: Jun 8, 2012
  2. jcsd
  3. Jun 8, 2012 #2
    Did you post this on the chevy forums? Those guys would be a lot better to give you direction on this, especially if its carbed.
  4. Jun 8, 2012 #3
    The chevy forum? No? Link?
  5. Jun 8, 2012 #4
  6. Jun 8, 2012 #5
    I thought you ment that there was a forum within the physics forums for chevys.

    Yes I am on a myriad of different websites. I like to keep my options open. I have had good help from the Physics forum in the past. Thought to post here and see what guys have to say.
  7. Jun 9, 2012 #6

    Ranger Mike

    User Avatar
    Science Advisor
    Gold Member

    welcome..querstions - what stall speed torque conveeter are you running?
    hopefully you have max trans oil cooler...
    i am not a bog fan of automatic trans in any form racing but to each his own...you have thebest flowing ports for max RPM..smaller ports and 1.98 valves would have helped but too late now..what is the header primary diameter and what type..4 in 1, tri Y? What carb are you thinking of? What oiling system yo urunning? wet or dri sump?

    both road courses you run are high wind tracks and very little elevation change but if you go to a mechnical track like MID OHIO or Road America with several hundered feet elevation change and reverse camber turns... you will need TORQUE...3000 to 6000 rpm range..

    i like a cam with LOTS of Lift and not so much duration..the 1.6 rockers are great idea but make sure you have proper oiling upstairs..the vlave springs are the weak link to the SBC longevity so make sure you got the plumbing right...btw the old 327 block only used filtered oil on the front 4 mains...i love the 327 and think it is THE best comp engine chevy made...thje 302 was 327 block and 283 crank originally before purpose build block from chevy came out..big bore short stoke..hi revs

    i would say forget the top end and concetrate on coordinating the drive train for mid range...that is where the engine will be 90 % of the time..only Wide Open Throttle on a few occassions per lap...and pay particular attention to the BRAKES..you will find that you win more races out braking the other guy than powering past him on the straights,,
    my opinion
    Last edited: Jun 9, 2012
  8. Jun 14, 2012 #7
    Have you called Comp Cams for their opinion?

    How long are your races? Why the auto and why a flat tappet cam? Is it a vintage class or something else? Do you have a casting or part number for the heads? What rule restrictions are you working with?
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