Re: Trap RPM
[Re: DusterKid]
#2923839
05/18/21 09:20 AM
05/18/21 09:20 AM
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Joined: May 2019
Posts: 712
Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 712
Lake Villa Il
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I think you'll find that shift rpm won't make much difference in trap rpm.
You'll need to tighten the converter, change the gears or run taller tires. (or make less power)
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Trap RPM
[Re: DusterKid]
#2923930
05/18/21 11:45 AM
05/18/21 11:45 AM
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Joined: Aug 2003
Posts: 43,141
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,141
Bend,OR USA
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Think about what happens when you short shift it or hold it longer before shifting it  What I remember is if I move the shift RPM up in both gears it spends less time in high gear, if I short shift it it spends a longer time in high gear  Go test and find out   Try shifting 300 RPM higher and then 500 RPM in both gears and look at the 330,660, 1000 ft. and 1/4 mile time and MPH differences 
Last edited by Cab_Burge; 05/18/21 11:47 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Trap RPM
[Re: DusterKid]
#2923936
05/18/21 11:51 AM
05/18/21 11:51 AM
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Joined: Jan 2003
Posts: 31,016
Oregon
AndyF
I Win
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I Win
Joined: Jan 2003
Posts: 31,016
Oregon
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If I wanted to lower the RPM I cross the finish line at would it be better to short shift or shift at a higher RPM? Trans is a 727, (I know a gear change or taller rear tire would be the idea way, but trying to avoid that at the moment). Are you trying to slow the car down or are you trying to go the same speed with less RPM? If you want to slow the car down then use a rev limiter or your right foot. If you want to go the same speed at a lower engine speed then you probably need to change gearing as well as the converter. Just changing gearing or tire size typically doesn't change engine RPM very much with an automatic since the converter slips more with the additional load.
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Re: Trap RPM
[Re: Locomotion]
#2923952
05/18/21 12:35 PM
05/18/21 12:35 PM
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Joined: Jan 2003
Posts: 9,991
Frostbitefalls MN (Rocky&Bullw...
gregsdart
master
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master
Joined: Jan 2003
Posts: 9,991
Frostbitefalls MN (Rocky&Bullw...
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What are your future goals? Head in that direction, not away from it. If your future includes more power, is your current rear strong enough? You may want to kill 2 birds with one stone. An example is a truck dana can be found with 4.10 ratio. Narrow it with good axles and you are set up to run low tens footbraking.
To further this discusion, what motor, rear and rpm are you at now?
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Trap RPM
[Re: gregsdart]
#2923959
05/18/21 12:54 PM
05/18/21 12:54 PM
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Joined: Jan 2005
Posts: 1,772
Keymar, MD
DusterKid
OP
top fuel
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OP
top fuel
Joined: Jan 2005
Posts: 1,772
Keymar, MD
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Not trying to slow the car down any, but if it does not that big of a deal as I bracket race. The backstory is I used to run 29.5x13.5 tires and a 4.56 gear. I always shifted at 6,000 would trap around 6500 or so. I than put 31x14 tires on the car and that brought the trap rpm down to around 6200-6300. I have since went from 440 source heads to Trick Flow 240's. I need new tires last year and I wasn't planning on doing any 1/4 mile racing since alot of stuff around me is headed to the 1/8th mile program. I went back to the 29.5x13.5 tires as they seem to work a little better and I wasn't concerned with rpms since I was only plan on running 1/8th mile. With the Trick Flows I'm making more power so the car is pulling alot better. Been out twice this year and I moved my shift point from 6000 to 6400 to try and bring the trap rpm down, but it's right around 6600. Engine is a .040 10.9:1 440, stock stroke, eagle rods, MP .557 cam, Victor Intake, 850 Proform Carb, 727 with 8" 5000 stall, Dana 60 4.56s, 3200lb with driver race weight. Went a 10.57 @ 125 this weekend. I suspect with the projected weather forecast and hot weather coming I'll loose 1-200 rpm going thru the traps due to the weather for the summer months. Prob will go back to a 31" tire next time, but don't really want to replace a new pair of slicks was just looking for ways around that at the moment.
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Re: Trap RPM
[Re: Cab_Burge]
#2923968
05/18/21 01:13 PM
05/18/21 01:13 PM
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Joined: Mar 2011
Posts: 3,070
Michigan
A727Tflite
master
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master
Joined: Mar 2011
Posts: 3,070
Michigan
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Think about what happens when you short shift it or hold it longer before shifting it What I remember is if I move the shift RPM up in both gears it spends less time in high gear, if I short shift it it spends a longer time in high gear Go test and find out Try shifting 300 RPM higher and then 500 RPM in both gears and look at the 330,660, 1000 ft. and 1/4 mile time and MPH differences The part about testing - that’s what you want to do. In this case it’s called a shift loop. Test one thing and one thing only. Like Cab said, try shifting the 1-2 and 2-3 at 6000 and see what it does at the stripe Then move the 1-2and 2-3 to 6500 and see what happens.
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Re: Trap RPM
[Re: A727Tflite]
#2923993
05/18/21 02:41 PM
05/18/21 02:41 PM
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Joined: May 2019
Posts: 712
Lake Villa Il
INTMD8
super stock
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super stock
Joined: May 2019
Posts: 712
Lake Villa Il
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More or less time in high gear by changing 1-2 shift point still isn't going to change (hardly) rpm through the traps though it will affect ET.
Weight/aero vs horsepower. It's going to trap similarly no matter what. (mph and rpm).
Unless you're talking about holding out on the 1-2 shift until it noses over or runs into valvetrain instability but I don't think that's going to help anything.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Trap RPM
[Re: DusterKid]
#2924030
05/18/21 04:02 PM
05/18/21 04:02 PM
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Joined: Dec 2006
Posts: 1,178
Indy
FlyFish
super stock
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super stock
Joined: Dec 2006
Posts: 1,178
Indy
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If you want less RPM at the stripe, just find a good spot to lift. Last year when I ran 1/4 mile I was bouncing off the limiter at the big end of the track, I decided to just lift at the 1000' mark as a work around until I got a higher RPM chip.....turns out, the car ran REALLY consistent lifting at 1000'....won quite a few races with that setup because it threw people for a loop. My car was running 10.4x lifting at 1000' and only trapping about 108mph. I plan on doing this some more this year too....other people must really like it too, because I've been told I'm number 1 using sign language quite a few times.....(just kidding....but not really).
67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....
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Re: Trap RPM
[Re: INTMD8]
#2924031
05/18/21 04:08 PM
05/18/21 04:08 PM
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Joined: Dec 2005
Posts: 11,550
Fulton County, PA
CMcAllister
Mr. Helpful
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Mr. Helpful
Joined: Dec 2005
Posts: 11,550
Fulton County, PA
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How much? A few hundred? A thousand? Spot drop. Top end throttle stop. Take away power. Add weight. Change the gearing/tire size.
Any .90 racer will tell you, you can kill a bunch up front and still run the MPH. Especially on a 1/4 mile track.
Last edited by CMcAllister; 05/18/21 04:09 PM.
If the results don't match the theory, change the theory.
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Re: Trap RPM
[Re: CMcAllister]
#2924107
05/18/21 07:37 PM
05/18/21 07:37 PM
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Joined: Dec 2005
Posts: 1,495
Shelby mi.
JAKE68
pro stock
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pro stock
Joined: Dec 2005
Posts: 1,495
Shelby mi.
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i dont under stand what is wrong with that rpm? you have a good rod that can handle a lot more rpm than that. with that power level its not like a few hundred rpm is going to be any easier on the motor. run it.
JAKES AUTOMOTIVE
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Re: Trap RPM
[Re: DusterKid]
#2924283
05/19/21 10:43 AM
05/19/21 10:43 AM
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Joined: Jan 2003
Posts: 9,991
Frostbitefalls MN (Rocky&Bullw...
gregsdart
master
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master
Joined: Jan 2003
Posts: 9,991
Frostbitefalls MN (Rocky&Bullw...
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Not trying to slow the car down any, but if it does not that big of a deal as I bracket race. The backstory is I used to run 29.5x13.5 tires and a 4.56 gear. I always shifted at 6,000 would trap around 6500 or so. I than put 31x14 tires on the car and that brought the trap rpm down to around 6200-6300. I have since went from 440 source heads to Trick Flow 240's. I need new tires last year and I wasn't planning on doing any 1/4 mile racing since alot of stuff around me is headed to the 1/8th mile program. I went back to the 29.5x13.5 tires as they seem to work a little better and I wasn't concerned with rpms since I was only plan on running 1/8th mile. With the Trick Flows I'm making more power so the car is pulling alot better. Been out twice this year and I moved my shift point from 6000 to 6400 to try and bring the trap rpm down, but it's right around 6600. Engine is a .040 10.9:1 440, stock stroke, eagle rods, MP .557 cam, Victor Intake, 850 Proform Carb, 727 with 8" 5000 stall, Dana 60 4.56s, 3200lb with driver race weight. Went a 10.57 @ 125 this weekend. I suspect with the projected weather forecast and hot weather coming I'll loose 1-200 rpm going thru the traps due to the weather for the summer months. Prob will go back to a 31" tire next time, but don't really want to replace a new pair of slicks was just looking for ways around that at the moment. As primarily a bracket racer i would shoot for absolutely the best consistancy you can get. Reduce the STR ( starting line ratio) with the tallest tire you can run and consider a taller gear. If you drop to a 4.10 ratio and go to a tall tire overall cosistancy will improve. The 1/2 shift affects et some because we are not perfect and even a slight rpm change means a little change in et. the later the shift comes, the more accurate you will be. Also reducing SLR and going big on tires will help you reach deadly consistancy. The cam you have is fairly small and reducing trap rpm to 6000 will pay dividends in a longer block life.
Last edited by gregsdart; 05/19/21 10:45 AM.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: Trap RPM
[Re: JAKE68]
#2924288
05/19/21 10:53 AM
05/19/21 10:53 AM
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Joined: Jan 2003
Posts: 14,494
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,494
So. Burlington, Vt.
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i dont under stand what is wrong with that rpm? you have a good rod that can handle a lot more rpm than that. with that power level its not like a few hundred rpm is going to be any easier on the motor. run it. I agree. 3.75” stroke, aftermarket rods, 6600....... no problem. I turned a little more than that in my 440 with heavy TRW’s and LY rods. I don’t advocate that, but I did it for years.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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Re: Trap RPM
[Re: fast68plymouth]
#2925818
05/23/21 01:04 PM
05/23/21 01:04 PM
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Joined: Aug 2007
Posts: 498
El Dorado Ca
65signet
mopar
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mopar
Joined: Aug 2007
Posts: 498
El Dorado Ca
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6600 is not to high for a 440 imo, and you have to remember its only there for a split second, it's not like your maintaining that rpm for extended period of time.
1965 Plymouth Barracuda 273 M/SA
1970 Plymouth Duster 360/904 10.60s with J heads
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