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I Hate Dragsters
DRR Sportsman
posted
I'll start out that I'm aware that are a multitude of variables that go into the equation...

What sort of 1/8 mile rpm change might one see changing from a 4.11 to a 3.89?

4.40 250 blower car, 34.5" tire, goes 7600 in the eighth at 160.

I've changed cam and converter since my last data (converter should be tighter and cam should move the powerband down a few hundred rpm)...the current gear has 12 years on it so i need to change it before the season starts.
 
Posts: 1172 | Location: somewhere between been and never was | Registered: November 03, 2002Reply With QuoteReport This Post
Mike Rietow
DRR Top Comp
posted Hide Post
quote:
Originally posted by I Hate Dragsters:
I'll start out that I'm aware that are a multitude of variables that go into the equation...

What sort of 1/8 mile rpm change might one see changing from a 4.11 to a 3.89?

4.40 250 blower car, 34.5" tire, goes 7600 in the eighth at 160.

I've changed cam and converter since my last data (converter should be tighter and cam should move the powerband down a few hundred rpm)...the current gear has 12 years on it so i need to change it before the season starts.


Converter is slipping 16-17% now 4.11.

It'll slip 18%-19% 3.89. 7400-7450-7500 rpm depending conditions.

1% room for error - tire growth variable.
 
Posts: 10487 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
The Bozman
DRR S/Pro
Picture of The Bozman
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150 max in my opinion, the convertor will do more than the gear change. what converter did you put in it, I have used an 05WAT, 06YAT and an 06WAT. They are all about 250 different.


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Posts: 5551 | Location: Gilmer, Texas | Registered: June 25, 2002Reply With QuoteReport This Post
I Hate Dragsters
DRR Sportsman
posted Hide Post
boz- it was originally a 05wat, didn't send it back to abruzzi. It's been into twice since, most recently 30 to 35 degree vane angle change.
 
Posts: 1172 | Location: somewhere between been and never was | Registered: November 03, 2002Reply With QuoteReport This Post
The Bozman
DRR S/Pro
Picture of The Bozman
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are you injected or carb? weight?


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Posts: 5551 | Location: Gilmer, Texas | Registered: June 25, 2002Reply With QuoteReport This Post
TOP38
DRR S/Pro
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I would say f going from a 4.11 to 3.89 and changing nothing else you will see around a 200 loss in rpm from 7600 to 7400 but the converter will have the last word!
 
Posts: 5422 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
I Hate Dragsters
DRR Sportsman
posted Hide Post
Carb, about 2050. Need to weight it
 
Posts: 1172 | Location: somewhere between been and never was | Registered: November 03, 2002Reply With QuoteReport This Post



wideopen231
DRR Top Comp
Picture of wideopen231
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I have seen gear change work both way. My 66 Nova broke 5.13,used a 4.86 we had a dropped.2 in 1/8.Lil brother had dragster with 496 BBC and changed 4.56.4.30 and 4.86 almost zero change et wise mph changed few. Guess it depends how well rest of combo work together.




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Posts: 12250 | Location: Greensboro NC | Registered: May 24, 2011Reply With QuoteReport This Post
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