Rpm drop at the shift

One of the most critical areas of a automatic race car

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supernova
Posts: 2552
Joined: Sat Feb 02, 2008 7:35 pm
Location: Ft.Worth Tx

Re: Rpm drop at the shift

#16 Post by supernova » Tue Aug 10, 2010 7:19 am

1/8 m only.
I'm on a 275/60/15 M/T D/R.
We're learning that this tire doesn't like the 4.30's

The motor was dyno'ed at one time before the head and intake work. I'm not sure what it makes now. 750 hp before n/a. Now? 830-850 I guess.
Blackhoodmafia!!!! :mrgreen: :mrgreen:

1972 Nova SS
572 C.I. BBC

Best to date: 1/8
et: 5.28
mph: 134
new wt. 3340 lbs

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Marty Chance
Posts: 193
Joined: Fri Sep 19, 2008 6:34 am
Location: Cheney, KS

Re: Rpm drop at the shift

#17 Post by Marty Chance » Wed Aug 11, 2010 8:41 am

unless you have some suspension mods that you can do, you will have to take gear reduction out of the rear end. You only want to make 1 change at a time, so if you are going to tighten the converter you may want to do that first and see if it will go down the track with just the stall change. It is possible that the tighter converter will make the tire spin worse BUT do not make more than one change at a time! it is also possible that the tighter converter will calm things down enough that it cures the tire spin. It would be to your advantage to have a good chassis man watch the car make a pass to make sure we are not overlooking a simple shock or suspension issue.
Marty Chance
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

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supernova
Posts: 2552
Joined: Sat Feb 02, 2008 7:35 pm
Location: Ft.Worth Tx

Re: Rpm drop at the shift

#18 Post by supernova » Wed Aug 11, 2010 9:53 am

Thanks Marty,
We are going back out this weekend for more testing. I set up a gear retard in the 7531 box to see if that helps.
I know the gear is steep but will continue to test to figure it out. A gear change might be in order.
Blackhoodmafia!!!! :mrgreen: :mrgreen:

1972 Nova SS
572 C.I. BBC

Best to date: 1/8
et: 5.28
mph: 134
new wt. 3340 lbs

User avatar
supernova
Posts: 2552
Joined: Sat Feb 02, 2008 7:35 pm
Location: Ft.Worth Tx

Re: Rpm drop at the shift

#19 Post by supernova » Mon Aug 16, 2010 9:22 pm

Ok, here's the deal. The 4.30's are gone....... Way to big for the 275/60/15 D.R.

The trans has a 1.80 low set in it. So my question is how low do I go with the gear? I'm thinking of a 3.60-3.70 gear there abouts.

What do you all think?
Blackhoodmafia!!!! :mrgreen: :mrgreen:

1972 Nova SS
572 C.I. BBC

Best to date: 1/8
et: 5.28
mph: 134
new wt. 3340 lbs

User avatar
Marty Chance
Posts: 193
Joined: Fri Sep 19, 2008 6:34 am
Location: Cheney, KS

Re: Rpm drop at the shift

#20 Post by Marty Chance » Thu Aug 19, 2010 7:58 am

3.70
Neal Chance Racing Converters
Home of the World's Fastest Automatic Doorslammers!
www.racingconverters.com

User avatar
supernova
Posts: 2552
Joined: Sat Feb 02, 2008 7:35 pm
Location: Ft.Worth Tx

Re: Rpm drop at the shift

#21 Post by supernova » Thu Aug 19, 2010 8:14 am

Ok, 3.70 it is.

Thank you Marty.

I'll have a progress report when we go out again with the new gear.
Blackhoodmafia!!!! :mrgreen: :mrgreen:

1972 Nova SS
572 C.I. BBC

Best to date: 1/8
et: 5.28
mph: 134
new wt. 3340 lbs

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