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Discussion Starter #1
Hey Folks,
I seldom post here, mostly just read. I hate to ask questions that have already been asked. Anyways i went to the track on saturday and feel as though the car is running great but perhaps laying down a bit from the 1/8 to the 1/4. First, heres my combo:

347 (10.8:1)
AFR 185s (box stock with upgraded springs)
FTI custom cam (.613/.578 , 244/[email protected])
Vic Jr. Intake
Holley 750HP out of the box
MSD 7al-2 ignition/MSD dizzy
C4 with a brake, 9" 3000 rpm converter
4.10's
26" ET Drags
Race Weight = 2880 (with me in it)
150 shot of nitrous

Now for the timeslip:

R/T: .278 (yeah, yeah)
60': 1.461
330': 4.147
1/8: 6.461
mph:104.78
1000': 8.516
1/4: 10.295
mph: 125.35

I am hitting the traps at about 6880 rpm. I know this because my shift light (6800) is on before i hit the traps, yet i don't hit the chip (7000).

If my calculations are right, i should be doing about 129-130 mph.

I think perhaps i am just over-revving the car and running out of gear before the traps.

Please, any educated ideas would be very helpful!

THANKS!
 

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Discussion Starter #3

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you have to factor in converter slippage.
 

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Discussion Starter #7
Both good possibilities..........i didn't factor in converter slippage. Wouldn't the converter slip uniformly throughout the entire run? As i said before, the first part of the timeslip is dead on. I am starting to think more gear/more tire....any other thoughts?
 

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Nitorus pressure could be dropping off at the top end the run...

Do you have a bottle warmer & pressure gauge?

What is the pressure at the beggining of the pass?

Should be 950 to no higher than 1000 psi
 

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Discussion Starter #9
i had plenty of pressure from the get go...950+, 900 after the traps. I don't think that was the problem, but who knows.
 

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On a 26" tire, going through at 6800 is about on par.

I have a 4400 stall on my n/a 427, went through at 128 mph at 6800 on a 325/50 drag radial that measured 28" tall exactly but had no tire growth.

I would think to crack a [email protected] your sixty foot would be more like a 1.40-1.42. I went 1.43 sixty, [email protected] mph and 1.44 sixty, [email protected] so it seems a little off there.

Try a 28" tire and shifting it a little lower in the rpms, like 6400. Nitrous is tq in a bottle, it should not require those kind of rpms to keep the car moving good.

Is 3000 rpm as high as the converter will go on the transbrake? It actually seems a little on the tight side, but should be OK for spray.
 

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Discussion Starter #11
On a 26" tire, going through at 6800 is about on par.

I have a 4400 stall on my n/a 427, went through at 128 mph at 6800 on a 325/50 drag radial that measured 28" tall exactly but had no tire growth.

I would think to crack a [email protected] your sixty foot would be more like a 1.40-1.42. I went 1.43 sixty, [email protected] mph and 1.44 sixty, [email protected] so it seems a little off there.

Try a 28" tire and shifting it a little lower in the rpms, like 6400. Nitrous is tq in a bottle, it should not require those kind of rpms to keep the car moving good.

Is 3000 rpm as high as the converter will go on the transbrake? It actually seems a little on the tight side, but should be OK for spray.
Yest 3000 is as high as she'll go on the 'brake. I know its tight, but on the spray, 3000 is where the torque is. N/A its a donkey out of the hole, but not the point.

I talked to Ed Curtis at FTI today and he said to perhaps tighten up the converter a bit (something with more efficiency %) or try new gearing. Since my tires are new, i'm going to swap in a set of 3.73s at try this again. He agrees i should be in the 129-130 neighborhood. The swap will be free, so i'll start there, and try and avoid another $800 converter :)
 

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Yest 3000 is as high as she'll go on the 'brake. I know its tight, but on the spray, 3000 is where the torque is. N/A its a donkey out of the hole, but not the point.

I talked to Ed Curtis at FTI today and he said to perhaps tighten up the converter a bit (something with more efficiency %) or try new gearing. Since my tires are new, i'm going to swap in a set of 3.73s at try this again. He agrees i should be in the 129-130 neighborhood. The swap will be free, so i'll start there, and try and avoid another $800 converter :)
Yeah, definitely try the gears first, 3.73 is a good gear and with those on a 28x10.5 tire I went 131 at 6800 with the same 4400 9" converter.

What brand is the converter you are using? A 9" converter should still be fairly efficient percentage wise, I just kind of think you're running out of gear and useable rpm which is why its flattening out up top.

Try the gear and if it helps, then try a 27" or 28" tire to see if it helps even more. 3.73 was a very good all around gear for me, got me through from stock motor on a little spray, to 347 on a little spray to 427 and down to [email protected] mph.
 

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Discussion Starter #13
I am running an Art Carr 9" converter. I think the problem is a little bit converter, and a little bit gear. As Ed said, a tire/gear size change isn't going to fix an inefficient converter, but it will keep it performing in a more efficient rpm band. Me and my buddy have both have track cars, and he's on a 28" tire with 3.73's. We are just going to make an even swap at my shop next weekend. We have more of eachother's stuff in eachother's car! Anyways we are hitting the track in october, so i will update with my results. Thanks for the great input White90GT!
Yeah, definitely try the gears first, 3.73 is a good gear and with those on a 28x10.5 tire I went 131 at 6800 with the same 4400 9" converter.

What brand is the converter you are using? A 9" converter should still be fairly efficient percentage wise, I just kind of think you're running out of gear and useable rpm which is why its flattening out up top.

Try the gear and if it helps, then try a 27" or 28" tire to see if it helps even more. 3.73 was a very good all around gear for me, got me through from stock motor on a little spray, to 347 on a little spray to 427 and down to [email protected] mph.
 
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