60 ft frustration is driving me nuts
#2785702
06/15/20 01:08 PM
06/15/20 01:08 PM
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Joined: Mar 2006
Posts: 9,835 MI, usa
dvw
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OP
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Joined: Mar 2006
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MI, usa
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Though we won last weekend the car hasn't been good. 60ft varies wildly. 3 different tracks. This weekend rd 1 1.40, rd 2 1.29. Its been as wide a spread as 1.29-1.46. Car leaves flat, deviously 12-16" up for 40-60foot out. What I've done to try and fix it. New M/T 10.5wx31, loosened the shocks and tightened the shocks, the fronts as many as 15 clicks. Varied tires 12-15 psi. Then with video realized there is zero tire spin . Next swapped converters, new plugs, cap, rotor, carbs apart cleaned and adjusted. Varied timing by 6 degrees. Same leave rpm, water, oil temp, intake temp. Incrementals after 60ft are spot on. Same fuel I've always run, Renegade Pro114. R/T are getting slow also. However on the practice tree they're fine. Foot brake only. Leave at 2700-3300. Eddy 750 carbs. The combo has been untouched and pretty decent for 7 years. Thoughts? Doug
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Re: 60 ft frustration is driving me nuts
[Re: dvw]
#2785708
06/15/20 01:24 PM
06/15/20 01:24 PM
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Joined: Jan 2003
Posts: 10,022 MN
JERICOGTX
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If the 330', 660' and 1000' are the exact same, I wouldn't worry about it. Could be where your car is tripping the 60' timers.
69 GTX
68 Road Runner
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Re: 60 ft frustration is driving me nuts
[Re: dvw]
#2785709
06/15/20 01:28 PM
06/15/20 01:28 PM
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Joined: Jan 2003
Posts: 19,363 Las Vegas
Al_Alguire
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Well I would be looking hard to the converter. Reaction times obvious would change with tire slippage, but if it is dead hooking and running slow on the tree and 60' I would be looking for a converter to toss in it for sure. Might look at the trans as well but sure sounds like a converter issue to me. Just went through this on a biddies S/ST car. Pulled converter and found some fins had been knocked loose from brazing, same deal. Reaction times and 60's inconsistent down track was fine.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: 60 ft frustration is driving me nuts
[Re: JERICOGTX]
#2785711
06/15/20 01:29 PM
06/15/20 01:29 PM
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Joined: Aug 2003
Posts: 4,676 On the parachute mount
n20mstr
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On the parachute mount
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If the 330', 660' and 1000' are the exact same, I wouldn't worry about it. Could be where your car is tripping the 60' timers. ARE your result different at different tracks? Maybe they have 60" light at different heights ? ALso do you have a transmission blanket? possible sometimes its hanging down?? Also the diff reaction times same thing, maybe the rollout is different form one track to another
....BAD A$$ STREET CAR.....
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Re: 60 ft frustration is driving me nuts
[Re: dvw]
#2785745
06/15/20 02:43 PM
06/15/20 02:43 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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Does your trans allow converter pressure changes?
"use it 'till it breaks, replace as needed"
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Re: 60 ft frustration is driving me nuts
[Re: TRENDZ]
#2785759
06/15/20 03:33 PM
06/15/20 03:33 PM
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Joined: Mar 2006
Posts: 9,835 MI, usa
dvw
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We have about 15 good videos of the rear tire from the last 4 weekends.There is ZERO tire spin. I thought converter as well. So it was swapped about 20 passes ago. The trans was gutted then also. saw nothing. The 1st converter is at the shop . Getting opened up this week. Its had the issue with both converters. It's lame right at the hit. 2 pretty knowledgeable guys say they can hear it sound flat directly after the throttle is floored. The play back tach thinks that there is a peak around 3400 rpm. The tach has always done this since I've been running the car. The other thing is it will idle at 1500 with the carb speed screws backed out all the way (throttle plates closed). I'm assuming vacuum leak. Checked the carbs, carb adapter plates, and manifold lid. I'll pull the lower intake this week. It puzzles me if it is an intake leak, why it doesn't consistently run poorly? it has no adjustment for the converter pressure. Doug
Last edited by dvw; 06/15/20 03:36 PM.
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Re: 60 ft frustration is driving me nuts
[Re: dvw]
#2785798
06/15/20 05:56 PM
06/15/20 05:56 PM
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Joined: Aug 2009
Posts: 235 Central Mississippi
mopar97
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Though we won last weekend the car hasn't been good. 60ft varies wildly. 3 different tracks. This weekend rd 1 1.40, rd 2 1.29. Its been as wide a spread as 1.29-1.46. Car leaves flat, deviously 12-16" up for 40-60foot out. What I've done to try and fix it. New M/T 10.5wx31, loosened the shocks and tightened the shocks, the fronts as many as 15 clicks. Varied tires 12-15 psi. Then with video realized there is zero tire spin . Next swapped converters, new plugs, cap, rotor, carbs apart cleaned and adjusted. Varied timing by 6 degrees. Same leave rpm, water, oil temp, intake temp. Incrementals after 60ft are spot on. Same fuel I've always run, Renegade Pro114. R/T are getting slow also. However on the practice tree they're fine. Foot brake only. Leave at 2700-3300. Eddy 750 carbs. The combo has been untouched and pretty decent for 7 years. Thoughts? Doug Have you checked to see if the advance in the distributor is functioning correctly? Provided that is not an issue, I too wonder about the AF screws being all the way out making no change. It does appear to be a vacuum related problem, the idea to check the intake gaskets is a good one but also the carb base and those gaskets also. Good Luck
Mopar born, Mopar breed, when I die, call me Mopar dead!
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Re: 60 ft frustration is driving me nuts
[Re: mopar97]
#2785803
06/15/20 06:24 PM
06/15/20 06:24 PM
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Joined: Jan 2003
Posts: 19,363 Las Vegas
Al_Alguire
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I Live Here
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What ignition is on it, also check for vacuum leaks. Was the converter you swapped in a known piece? I would want to hear whats said from the converter guy myself. Have you noticed a change in shift recovery or flash at all? I cant see a vacuum leak causing this issue with 60's and lights and not downtrack, but who knows. I mean if its got a leak at idle and down low it would get worse up top one would think.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: 60 ft frustration is driving me nuts
[Re: mopar97]
#2785812
06/15/20 06:36 PM
06/15/20 06:36 PM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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With changing converters, the next thing I would check is the stator shaft. Be sure the splines are ok and that it is not able to spin in its mounting. Never daw this with a TF, but many times on GM trans.
"use it 'till it breaks, replace as needed"
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Re: 60 ft frustration is driving me nuts
[Re: TRENDZ]
#2785847
06/15/20 08:23 PM
06/15/20 08:23 PM
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Joined: Mar 2006
Posts: 9,835 MI, usa
dvw
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It does have the pink/red gaskets so that's on the list. They were replaced about 100 passes ago when the heads were off. Its MSD crank trigger, MSD 7AL 2 box, MSD 8201 pro power coil, Taylor 8mm wires NGK 8 plugs. Shift fall back with converter 1 was around 900, with converter 2 800. Converter 2 is a known piece from ATI built for a 936 hp 572, had 40 passes since new when installed. The incrementals 60/330 330/660 are nearly dead on going back to 2018. Both are 9.5 cores which outwardly appear to be the same core style. Stator shaft support was replaced about 40 passes ago. Its tight and splines are nice. Always careful with the idle screws as you say this is a known problem. My friend has a similar engine that has been dynoed at Best. Same intake with a a pair of Pro Systems 950's. Going to just switch the entire upper half with his upper and carbs. Doug
Last edited by dvw; 06/15/20 08:25 PM.
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Re: 60 ft frustration is driving me nuts
[Re: dvw]
#2786000
06/16/20 12:28 PM
06/16/20 12:28 PM
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Joined: Jan 2003
Posts: 19,363 Las Vegas
Al_Alguire
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I Live Here
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Be interesting to see what you find .I just don't see the intake or carbs causing such an issue with reaction time and 60' but run great at the other end. Those kind of things generally don't clear up down track and get better.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: 60 ft frustration is driving me nuts
[Re: HardcoreB]
#2786303
06/17/20 11:11 AM
06/17/20 11:11 AM
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Joined: Jan 2003
Posts: 19,363 Las Vegas
Al_Alguire
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I Live Here
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Rich at the hit is typical for anything that spends time on the brake for sure, never seen it cause an issue like he is having though. I have seen 10-1 fat conditions at the hit. A combination of lots of carb and being on the two step dropping cylinders will cause it. If it was a over rich condition a quick review of video could help confirm that, one would think if it is bad enough to cause the car to slow that much there would surely be signs of it on the video. I think it would need to be WAY fat to cause that. But ya never know I suppose. Only other way I have seen that happen is fuel dumping out the vents that will create a bog for sure and a tell tale puff of smoke, but he says it dead hooks and goes so don't see it being anything like that. Kinda like an intake leak, it should be present all the way down the track, cannot imagine that would repeat from knonw good runs with the extra air. Unless we are assuming it is "sealing" itself with more heat?
IMO most people run WAY to much fuel pressure to begin with, usually to mask an inadequate fuel system. My car is at 4.8 lbs throughout the run. Data logging might certainly help to narrow this down for sure. Would love to see a driveshaft and an acceleration graph for sure.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: 60 ft frustration is driving me nuts
[Re: Al_Alguire]
#2786354
06/17/20 12:38 PM
06/17/20 12:38 PM
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Joined: Jan 2003
Posts: 4,048 Shelby Twp. Mi
HardcoreB
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Rich at the hit is typical for anything that spends time on the brake for sure, never seen it cause an issue like he is having though. I have seen 10-1 fat conditions at the hit. A combination of lots of carb and being on the two step dropping cylinders will cause it. If it was a over rich condition a quick review of video could help confirm that, one would think if it is bad enough to cause the car to slow that much there would surely be signs of it on the video. I think it would need to be WAY fat to cause that. But ya never know I suppose. Only other way I have seen that happen is fuel dumping out the vents that will create a bog for sure and a tell tale puff of smoke, but he says it dead hooks and goes so don't see it being anything like that. Kinda like an intake leak, it should be present all the way down the track, cannot imagine that would repeat from knonw good runs with the extra air. Unless we are assuming it is "sealing" itself with more heat?
IMO most people run WAY to much fuel pressure to begin with, usually to mask an inadequate fuel system. My car is at 4.8 lbs throughout the run. Data logging might certainly help to narrow this down for sure. Would love to see a driveshaft and an acceleration graph for sure. His car is always a footbraked. And was thinking it was LEAN until it got a stronger signal to the carbs. I would think down track, a localized signal loss has less affect than it would during that footbrake transition. I have seen a few manifold leaking conditions where it wouldn't be obvious there was a problem based on downtrack performance...other than idle.
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Re: 60 ft frustration is driving me nuts
[Re: tabletop390]
#2786572
06/17/20 08:03 PM
06/17/20 08:03 PM
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Joined: Dec 2012
Posts: 1,823 Wind Gap,Pa.
Sammy
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We just ran into something similar on a buddy’s car and the fix believe it or not was a new master switch. The initial hit and vibration off the line and during the burnout was causing the disconnects and reconnects and making his MSD go nuts. Once he got out around 30-40 ft car settled and didn’t vibrate as much and ran like a champ. We did everything, converters, carbs, rebuilt the trans, etc. How did you figure out that was the problem?
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