Page 1 of 2 12 LastLast
Results 1 to 10 of 17

Thread: hesitates

  1. #1
    Senior Member MASTER BUILDER
    Join Date
    Jan 2007
    Location
    winner sd
    Posts
    196

    hesitates

    have a small hesitation when i launch below 2800. have a 750dp. has 50cc pumps, 31 squirters. the linkage isn't 1-1. should i go to bigger squirters and 1-1 on the linkage or something else. thanks, charlie

  2. #2
    Senior Member DYNO TECH
    Join Date
    Feb 2004
    Location
    Leonard, Texas
    Posts
    414
    How is the accelerator pump set up? Are you ft braking?
    'A government big enough to give you everything you want, is big enough to take away everything you have.'

    Thomas Jefferson


    http://www.adinms.com/sitebuildercon...junkresize.jpg

  3. #3
    Senior Member MASTER BUILDER
    Join Date
    Jan 2007
    Location
    winner sd
    Posts
    196
    pumps are set up as per holleys' recomendations so as not to bottom out at full throttle. am footbraking. have a 3500 stall.

  4. #4
    Senior Member RACING JUNKIE jmarksdragster's Avatar
    Join Date
    Jul 2007
    Location
    Florida
    Posts
    635
    You should not need 50cc pumps on a 750DP, put the 30cc back on. Do you have mechanical advance in the distributor? Try running more initial and see if it goes away but don't run it out, you will have to much total possibly. If it does, limit the amount of advance in the curve to give more initial without changing the total, or bring it in earlier. All your info on the engine/vehicle would help.
    Mark Whitener
    http://racingfuelsystems.myfunforum.org
    __________

    Good work isn't cheap, and cheap work can't be good.

  5. #5
    Senior Member MASTER BUILDER
    Join Date
    Jan 2007
    Location
    winner sd
    Posts
    196
    carb came with 50s on it. should i have 50 in front and 30 rear or try 30 all the way. have tried dif timing. seems to like 34 total at 3200 the best for et. have mech advance and no vacume advance. don't have any black smoke when i launch is why i was thinking on too small of squirters.

  6. #6
    Senior Member DYNO TECH
    Join Date
    Feb 2004
    Location
    Leonard, Texas
    Posts
    414
    Quote Originally Posted by sds10racer
    pumps are set up as per holleys' recomendations so as not to bottom out at full throttle. am footbraking. have a 3500 stall.
    Not saying the other advice is wrong, just don't do more than one change at a time so you know what works.

    First off, since your ft. braking set the front pump so when your staged and at stall speed, you haven't used the entire shot before you need it. The stumble could be caused by not having enough initial shot left. When your at launch RPM you should still have almost all of your front pump shot left. May have to mess with the nozzle size and pump cams to get it right. This should also help your launch. Definately keep the 50cc on the front, 30 on the back should be fine.

    How much total timing are you running now and what RPM does your full advance come in?
    'A government big enough to give you everything you want, is big enough to take away everything you have.'

    Thomas Jefferson


    http://www.adinms.com/sitebuildercon...junkresize.jpg

  7. #7
    Senior Member RACING JUNKIE
    Join Date
    May 2006
    Posts
    2,044
    Good advise blittle common problem overlooked by most tuners when footbraking.


    But I still have some questions on your set-up s10.

    What size motor is this?
    What tranny?
    Rear gears?
    Cam?
    Intake?

    I kinda need more info.
    ***IN GOD WE TRUST***

  8. #8
    Senior Member RACING JUNKIE
    Join Date
    Sep 2007
    Posts
    4,143
    I had a 700 dp I bought new (years ago) and it had the 50 cc pump on the back when new...it was on a mild 406 and it would fall on it's face when you stomped it...put a 30 cc pump on and problem solved

  9. #9
    Senior Member MASTER BUILDER
    Join Date
    Jan 2007
    Location
    winner sd
    Posts
    196
    this is a 355 with a gm hot cam kit, vortec heads w 1.6 crane gold rollers, rpm air gap with 13/4 spacer. 4.86 gears, 31.10.50 w m/t. all this has got me down to 1.58-1.60 60ft and 11.74 1/4 mile and 115 mph. the timing at the time of these runs was 38 at 3600. have put a recurve kit in the dist and am going to mess with it at the track this weekend to see what will work best. am bringing up the rpm's to 2800 and leaving from there. any lower than 2500 and the hesitation comes in. it's a small one but enough to loose on the 60 ft time. the launch is hard enough to spin the rim 1/4 inc each time i leave. hope thats enough as i have to go back to work now thanks, charlie

  10. #10
    Senior Member DYNO TECH
    Join Date
    Feb 2004
    Location
    Leonard, Texas
    Posts
    414
    Quote Originally Posted by sds10racer
    this is a 355 with a gm hot cam kit, vortec heads w 1.6 crane gold rollers, rpm air gap with 13/4 spacer. 4.86 gears, 31.10.50 w m/t. all this has got me down to 1.58-1.60 60ft and 11.74 1/4 mile and 115 mph. the timing at the time of these runs was 38 at 3600. have put a recurve kit in the dist and am going to mess with it at the track this weekend to see what will work best. am bringing up the rpm's to 2800 and leaving from there. any lower than 2500 and the hesitation comes in. it's a small one but enough to loose on the 60 ft time. the launch is hard enough to spin the rim 1/4 inc each time i leave. hope thats enough as i have to go back to work now thanks, charlie
    Somewhere between 36 and 38 deg. should about right for that engine. If your spinning the rims in the slick you better get some screws in them. try some of the tuning techniques advised and I think your problem will go away. But remember do one change at a time. To many changes at once could make it worse and then you won't know where your tune up is.
    'A government big enough to give you everything you want, is big enough to take away everything you have.'

    Thomas Jefferson


    http://www.adinms.com/sitebuildercon...junkresize.jpg


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Email us - Support@RacingJunk.com
Call us - 866.326.9227
Copyright © 2005-2016 RacingJunk.com All Rights Reserved.

Designated trademarks and brands are the property of their respective owners. Use of this Web site constitutes acceptance of the RacingJunk.com
Terms of Use, Classifieds Disclaimer, Privacy Policy, and Cookie Policy