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Hesitation at lower RPMs #1113588 11/14/11 03:59 PM 11/14/11 03:59 PM
Joined: Jul 2003 Posts: 303 Virginia Beach, Va wtucker OP enthusiast
wtucker OP enthusiast Joined: Jul 2003 Posts: 303 Virginia Beach, Va	At WOT from 2600 +/- RPMs there is no stumble or hesitation, but anything before that at WOT it will stumble for a second before taking off. Do you think the stumble is fuel related at lower RPMs? Timing?

Re: Hesitation at lower RPMs [Re: wtucker] #1113589 11/14/11 04:08 PM 11/14/11 04:08 PM
Joined: Jan 2008 Posts: 3,886 Lost and Spaced B bboogieart master
bboogieart master B Joined: Jan 2008 Posts: 3,886 Lost and Spaced	Sounds like maybe the accelerator pump might not be working or giving too small a shot. This happens just when you floor it? Take off the air cleaner and give the throttle a blip and you should see a good squirt of gas. I have mechanical Aptitude. I can screw up anything.

Re: Hesitation at lower RPMs [Re: bboogieart] #1113590 11/14/11 04:13 PM 11/14/11 04:13 PM
Joined: Jul 2003 Posts: 303 Virginia Beach, Va wtucker OP enthusiast
wtucker OP enthusiast Joined: Jul 2003 Posts: 303 Virginia Beach, Va	I replace the original 30 with a 50cc, which helped. Could initial fuel pressure be to low? At idle its about 5.5, not sure what it goes to an WOT

Re: Hesitation at lower RPMs [Re: wtucker] #1113591 11/14/11 04:19 PM 11/14/11 04:19 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	What eng/carb/recent mods/always done it/cold and hot? So at part throttle it will hesitate for a sec then take off OK accelerating OK moderately at part throttle? CHeck float level/acell pump squirt tip in/duration. Ideally would be to tape a vac gauge to the windshield/run it to manifold vac & take it out & note the highest in hg it hesitates at after confirming the float/squirt is good. May need richer pri jets or "cruise" step (eddy) or a higher # PV and a vac leak would do it but for now assuming it is a lean tuning prob live every 24 hour block of time like it's your last day on earth

Re: Hesitation at lower RPMs [Re: wtucker] #1113592 11/14/11 04:58 PM 11/14/11 04:58 PM
Joined: Jan 2003 Posts: 24,562 Brookeville, Md Mr.Yuck Not enough dumb comments...yet
Mr.Yuck Not enough dumb comments...yet Joined: Jan 2003 Posts: 24,562 Brookeville, Md	need a bigger pump shot or some more timing. [IMG]http://i66.tinypic.com/pui5j.jpg[/IMG] Coming soon!!!!

Re: Hesitation at lower RPMs [Re: Mr.Yuck] #1113593 11/15/11 03:59 PM 11/15/11 03:59 PM
Joined: Jul 2003 Posts: 303 Virginia Beach, Va wtucker OP enthusiast
wtucker OP enthusiast Joined: Jul 2003 Posts: 303 Virginia Beach, Va	Eng 440 .30 over, street dominator, 850 Mighty Demon, 452 ported and milled .10, 238/244 huges Hyd cam, 2500 converter, 4.10 gears. It's been doing it for a while. I've changed to a bigger squirter 31 (I think), increased the primary jets 2 sizes. I tried changing to heavier and lighter springs in the dizzy. I'll try and give it more initial timing (currently about 12) and see what happens.

Re: Hesitation at lower RPMs [Re: wtucker] #1113594 11/15/11 04:45 PM 11/15/11 04:45 PM
Joined: Jan 2003 Posts: 2,757 Gilbertsville, PA 19525 P Pntastar69 master
Pntastar69 master P Joined: Jan 2003 Posts: 2,757 Gilbertsville, PA 19525	Adjust the acc pump. I had the same issue w/a 670 Holley at low rpm until I got in the throttle. It needed just a squirt to eliminate the hesitation.

Re: Hesitation at lower RPMs [Re: wtucker] #1113595 11/15/11 08:12 PM 11/15/11 08:12 PM
Joined: Feb 2005 Posts: 4,316 Prospect, PA BSB67 master
BSB67 master Joined: Feb 2005 Posts: 4,316 Prospect, PA	If it has a slight stumble or hesitation under light or part throttle acceleration at lower rpm, there could be something amiss in the idle/transition circuit of the carb as well.

Re: Hesitation at lower RPMs [Re: BSB67] #1113596 11/15/11 09:11 PM 11/15/11 09:11 PM
Joined: Feb 2010 Posts: 1,377 Ohio Todd pro stock
Todd pro stock Joined: Feb 2010 Posts: 1,377 Ohio	Had the same problem and went through the carb numerous times with jets accelerator pump shot adjustments with no change. Bumped the timing up to 18 initial and all in by 2200 and all the hesitation was gone.

Re: Hesitation at lower RPMs [Re: Todd] #1113597 11/15/11 11:23 PM 11/15/11 11:23 PM
Joined: Feb 2005 Posts: 5,221 Branson, Mo. J joedust451 super gas
joedust451 super gas J Joined: Feb 2005 Posts: 5,221 Branson, Mo.	Quote: Had the same problem and went through the carb numerous times with jets accelerator pump shot adjustments with no change. Bumped the timing up to 18 initial and all in by 2200 and all the hesitation was gone. I agree, more int. timing & most likely a faster curve, Vacuum is too low at 5.5 with a cam that size, low int. timing will do that. 75 Duster, 451 10.87 @ 123.58 NA 97 Z28 6sp., 12.01 @ 115 on a 100 shot 71 Swinger. 360 magnum. 12.58 @ 105 78 cutlass, 469 BBC. 12.70 @ 108 on street tires. http://www.youtube.com/watch?v=Z2kqNmMfheU

Re: Hesitation at lower RPMs [Re: joedust451] #1113598 11/15/11 11:29 PM 11/15/11 11:29 PM
Joined: Oct 2008 Posts: 116 Midwest M MoparsnMissiles member
MoparsnMissiles member M Joined: Oct 2008 Posts: 116 Midwest	Quote: Quote: Had the same problem and went through the carb numerous times with jets accelerator pump shot adjustments with no change. Bumped the timing up to 18 initial and all in by 2200 and all the hesitation was gone. I agree, more int. timing & most likely a faster curve, Vacuum is too low at 5.5 with a cam that size, low int. timing will do that. Same here, bump the timing up a few degrees. World of difference.

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