Camshaft duration for blown alky with powerglide

Discussion in 'InsideTopAlcohol.com Tech Questions' started by kevin_sine, Dec 14, 2010.

  1. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    II have a nostalgia funny car with a 511 kb hemi and powerglide trans.10in converter 5000 rpm stall.
    11.5:1 compression,fuel heads,14/71 24lb @30%,180 low gear,430 rear gears w 34.5 tires.
    Present cam has 294 duration @50 installed at 40deg btdc.fresh 110 pump.

    My problem is that it is down on power everywhere in the rpm range,best of 7.59 @175,1.12 60ft times.Launch rpm is 4000rpm and I suspect that is too low for this cam.
    This isn't a TAFC,just trying to get it to run in the 6.60-6.90 range.I have talked to a couple of cam company's and they all seem to say the same thing that the cam has too much duration.

    Have any of you guy's run a combination like this and what were the cam specs?

    Thanks for any help.
     
    #1
  2. SoDak

    SoDak Active Member

    Joined:
    Dec 29, 2006
    Messages:
    1,522
    Likes Received:
    3
    Not sure on the cam, but I noticed you said it has a fresh pump on it. Did the pump just get rebuilt and now your not going as fast?
     
    #2
  3. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    It has been a pig since I built it(the car).Pump is 3 runs fresh from spud miller.I had a 1100 on it before the 110 but removed it as it was suspect,that and it was way more pump than I needed.(I had a 175 in the loop)

    I have about 18 passes on this car,3 with the new(110)pump.
     
    #3
  4. hemi altered 378

    hemi altered 378 Blown Altered

    Joined:
    Jul 3, 2004
    Messages:
    864
    Likes Received:
    0
    Kevin....
    if i were you i would put the standard R-296/296-500 Crane cam in it and go. that cam will work just fine for you....give me a call sometime.
    Darren
     
    #4
  5. Mike Canter

    Mike Canter Top Dragster
    Staff Member

    Joined:
    Mar 10, 2004
    Messages:
    4,402
    Likes Received:
    125
    Darren, with his lower boost I think the 477 Crane cam would be a better choice. That is what is usually used with the 20% OD promods making in the 30's on boost
     
    #5
  6. KDavidson

    KDavidson Member

    Joined:
    Dec 7, 2005
    Messages:
    287
    Likes Received:
    0
    Kevin,

    Call Tim Cole @ Comp Cams. He set me up with a 115 cam for my Chevy than ran easy 6.90's and NEVER had to mess with the lash. And this was all below 7500 rpms with a 4000 RPM launch.

    He cetainly saved me a ton of grief.

    JMHO

    Keith
     
    #6
  7. 23T Hemmee

    23T Hemmee Member

    Joined:
    Jul 10, 2007
    Messages:
    449
    Likes Received:
    0
    294 Degrees @ .050 is right in line with about every blown/alky cam I've ever seen, if those two cam companies say its too much duration, they just trying to sell you a new cam. Are you absolutely sure about where the cam is installed, does your cam card give you a lobe centerline target to install at, would use that instead of just 40*BTDC, it sounds to me like the cam is way retarded, (don't ask me how I know...lol)How much mag timing are you running and what does the car weigh. And this is out in left field, is it standard or raised cam block and is it the right cam for either. If you have plenty of piston/valve clearance the 48* cam would run in a std, cam block, just not well. Just trying to think of possibilities.
     
    #7
  8. Moparious Maximus

    Joined:
    Feb 23, 2009
    Messages:
    399
    Likes Received:
    1
    I've got to agree with 23T on this one, 294* doesnt sound out of line, it may be a few degrees more than it really wants but that shouldnt make it run like a pig.

    Our cam is 285* intake and 292* exhaust, 15-17lb boost in a 572" with an 8-71, stalls at 5200 runs like a monster till about 8500.

    In my opinion you have another problem,
     
    #8
  9. SoDak

    SoDak Active Member

    Joined:
    Dec 29, 2006
    Messages:
    1,522
    Likes Received:
    3
    I agree, what valve spring pressure and magneto are you running?
     
    #9
  10. Ron C

    Ron C Jr. Dragster

    Joined:
    Mar 4, 2005
    Messages:
    487
    Likes Received:
    1
    What kind of cranking cylinder pressure do you have? That might tell the story of the cam.

    Blessings.........Ron Clevenger
     
    #10
  11. G Martin

    G Martin Member

    Joined:
    Aug 15, 2005
    Messages:
    65
    Likes Received:
    0
    I also think something else is not right. We ran a funny car with a 518 (old) fuel headed TFX with a centrifugal clutch leaving at idle, 2200 RPM, with similar cam, 2.08 low 3 speed lenco, 4.30 gear, 36" tall tires. With an old 14-71 standard rotor blower at 18% UNDERDRIVE it would run 7.50 all day long. At 40% overdrive it would run 6.60-6.70 at 215. Put on a new Littlefield with K-11's (only change made) at 21% overdrive and it runs easy 6.50 at 219.

    Greg
     
    #11
  12. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    385 on the seat.
    20 amp pro mag @34*
     
    #12
  13. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    195-210 psi
     
    #13
  14. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    Any idea what kind of boost # you were getting with that old 14-71?
    Mine is making 24lb but at what rpm is unknown.and it is pretty tired,I can spin it with one finger...:rolleyes:
     
    #14
  15. Scouder

    Scouder New Member

    Joined:
    Jan 2, 2009
    Messages:
    378
    Likes Received:
    0
    I have exactly the same setup you have, right down to the boost. My cam is an old Erson with 296 on both sides, and if I remember right it's installed at 37.5 degrees. With everything on the powderpuff setting, (fuel system fat, 28 degrees average timing, footbrake launch at idle, and shifting at 6500) we ran 4.6 at 160 in our dragster in the 1/8. I take that back. Now that I think of it, I was still running 3.89 gears, not the 4.30s. Anyway, as stated above, if it really is 294, then it isn't your duration causing the problem. Put that out of your mind and find the real problem. It could still be a bad cam, but it isn't the duration.

    Hope this helps.

    -Brian
     
    #15
  16. mikentracy718fc

    mikentracy718fc New Member

    Joined:
    Jan 5, 2006
    Messages:
    199
    Likes Received:
    0
    I ran a deal like yours in my alky car for some time and 34 deg with 11.5 never worked for me. At the time a had an old fuel 14-71 blower and 4.10s for a cifca deal. I wanted to step it up but could not get the boost up. I had 3 deg advance when I set the cam. It would not come alive untill I put more timming in it. I ran up to 38 deg and the only reason I hurt it is because my dumb A** hit the trans brake button about 350 feet. Ron C was there that day. That combo ran 6.80s easy with close to the same cam you have. Now I run 12.5 with a 4.56. I have taken some of Jim Oddys advice and she flys now. Just sayin
     
    #16
  17. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    Do you happen to remember how much boost you were making,and you're launch rpm?
    Thanks.
     
    #17
  18. mikentracy718fc

    mikentracy718fc New Member

    Joined:
    Jan 5, 2006
    Messages:
    199
    Likes Received:
    0
    With the timing back for cifca running 7.50s I made 28 lbs of boost launching at 4000 rpm and 7600 through the lights with the 4.10 in the rear. Just adding 4 deg of timing the boost went up to 36 lbs and 8200 through the lights. Not knowing your fuel system and other important data dont try what I did because what worked for me may not work for you. hey dose this mean your keeping your car???? I hated to see that you were selling it. Im going to put an old body on mine, Slow it down and run 7.0 pro since cifca and pafca are now gone. The north west would be a cool deal for me or back with you guys but im stuck in so cal.
     
    #18
  19. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    Thank you all for the advice.
    I guess I will keep this cam in it.
    Buy a couple new pulley's and a new belt and spin the blower a little harder.
    Try leaving a bit harder.
     
    #19
  20. kevin_sine

    kevin_sine New Member

    Joined:
    Sep 28, 2008
    Messages:
    37
    Likes Received:
    0
    I guess untill somebody buy's it I'll run it,I don't have much for match races down here in FL.That sucks about the CIFCA,that was a good circuit.If I go to BG next year I will run the 7.0 class again.
    I should not be bitchin too much we have been figuring this thing out,In the last 4 runs we have picked up 4/10ths.I just get pissed off when I have to keep pulling fuel away from it.
     
    #20

Share This Page