Need Some Help....

My Van is set up for S/G and S/ST, but I would like to run the 6.50 Index Class, which is popular around here.

The 6.50 Index Rules mean no throttle stops, delay boxes or timers. Since RPM Shifters are OK, that's what I plan to try.

Since my old set up was using a stop and timers, I have no good starting point. I will be starting from scratch trying to determine the RPM shift points. My first attempt was at South Georgia Motorsports Park (6.15 and a 6.17 using different shift points and chipping the motor down to 4500 off the line).



SGMP

..............60'...330'...660'....MPH..CHIP.SHIFT
1st Run 1.389 3.946 6.154 110.19 4500 6300
2ndRun 1.379 3.963 6.176 110.55 4500 5900



Gainesville was my 2nd test.


1stRun 1.597 4.462 6.759 107.42 3800 4800
2ndRun 1.586 4.457 6.760 107.04 3800 4800
3rdRun 1.413 3.987 6.194 111.02 3800 5800
4thRun 1.462 4.248 6.527 108.41 3800 5100


For a baseline, I lowered the starting line RPM Chip to 3800 and the shift point to 4800. The second pass I didn't change a thing so hopefully I would get a good baseline. Thinking it would give me a nice thousand ratio, I raised my shift point to 5800 for the 3rd pass. Then after the run I remembered I ran very similar run I had 2 weeks earlier. For the 4th run, I used 5100 as a shift point, and ran a 6.52, which is close to the target Index.




Fine tuning is now the problem because:

1. The chipped down motor at the start makes it hard to catch a 0.4 light.

2. A 100 RPM shift point may change ET almost a tenth. 100 is the smallest increment of adjustment on the RPM Box.




Possible Solutions I may try:

1. Put 4.88 gears back in to get off the line quicker.

2. Put 1.96 gearset in Glide.

3. Take some throttle out and run at 80% open.


Do you have any ideas or suggestions?


Setup: Van weighs 2700 lbs, with a DRAM built 496 low deck, making just under 700 hp, 1.76 Glide with 4.1 gears in the Dana, 14 x 32SS M/T

best way to do it is with a manual stop thats adjsutible. restrictor plates would work but take a lot of time to change. most everybody I know uses a manual. that way you can keep all of your shift points.

alot of people adjust weight as well. Adding a
couple hundred pounds will get you close.

I have had some trouble doing this also. I can't shift below my stall speed 7,300. This is a big problem. I ran a mechanical throttle stop and ran out of adjustment. In good air I can go 5.6's but most of the time I run 5.7 need to run 5.95 and 6.0. The throttle stop and 150 lbs of ballast got me as slow as 5.81. I am searching for a tighter converter so I can use the shift point more. Also looking to make some restrictor plates. I also tried a lot of timing retard it just killed the car off the line. This is a challenge unlike regular bracket racing where you dial what you can run. I like the concept just, like you, need to master the ET.

Leon

I have used a restrictor plate before. It was not the ticket for me. It takes away from driving the finish line with the throttle. You lose a ton of throttle response down track.

a manual adjustable stop is the way to go in most cases, although some rules say you cant use those. In that case an adjustable throttle cable is the ticket. The throttle cable is what I use. I have used it to run open comp and slow down to 7.0 also. ( my car runs 6.20s and 30s ) A good cable bracket like the Jegs brand one is easy to mark and measure for adjustments between rounds.

Played with the throttle cable today. There is 70 degrees in the throttle blade travel, open to closed. Two rounds on the cable equals 12 degres in the throttle blades.

So has anybody played with shutting down the carb? How far do you have to close it before it starts making a difference.

You can try pulling timing out of it.

My car is heavy. So, it doesnt take much adjustment for me to slow a tenth. I never thought to measure it in degrees.

This is what I use.

http://www.jegs.com/i/JEGS/555/15235/10002/-1

I can adjust using the slide and also with the cable end.

unhooking the back throttle blades usually kills .03

This is the graph from run #2 above. The shift point is 4800. The starting line chip is 3800. When I let off the trans break it flashes past my shifting point.

As you can see by the graph it looks like it shifts into high before the van even moves. It either takes a little time to shift or the enertia gives a very quick spike on the driveshaft line. The whole run is in high.