Rear Gear Ratio - 1/8 mile bracket racing a 904 like a Powerglide

[TMP67]

Looking for input on a rear gear ratio for 1/8 mile bracket racing. I only bracket raced 1320 in the past. Basically build a mid to low 8 second street/strip package small block (under 6k RPM). Low gear 904, 28.0 radial slick, 10" wheel. The goal is crossing the 1/8 mile stripe in second. I am thinking a 3.23, 3.55 or ? Any examples of experience would be appreciated. Thanks!

 

[AJ/FormS]

depending on your convertor slip, 6000 with 3.23s and a 1.54 Second, will get you from 100 at zero-slip, to 95 at 5% slip, at average thru the markers..

 

[rmchrgr]

Chck out the Wallace calculators. They have other calculators on their page besides the one below. Like said above, you generally need to know things like converter slip, HP (at the wheels) weight and rpm.

Wallace Racing 1/8 mile gear calculator

 

[PROSTOCKTOM]

Is this a dedicated race car, or a street strip car?

If it's race only I would say 4.10 if you only have 6000 rpms to work with.

I used to race car that had 28" x 9" slicks and would turn 7000 rpms. I ran a 5.13 in that car 1/8th mile racing.

Tom

 

[TMP67]

Chck out the Wallace calculators. They have other calculators on their page besides the one below. Like said above, you generally need to know things like converter slip, HP (at the wheels) weight and rpm.

Wallace Racing 1/8 mile gear calculator

Yes, I have run their 'Gear-RPM-MPH-Tire Diameter' calculator that includes the transmission ratio input and converter slippage %. Good for getting a base. Out fishing for some real world input. Thanks!

 

[TMP67]

Is this a dedicated race car, or a street strip car?

If it's race only I would say 4.10 if you only have 6000 rpms to work with.

I used to race car that had 28" x 9" slicks and would turn 7000 rpms. I ran a 5.13 in that car 1/8th mile racing.

Tom

Street / Strip deal. Thanks!

 

[33IMP]

I have no real world experience, (with what you are trying, that is) but....
Assuming an 8 3/4, I would think a 3.23 would be your best choice. Any higher, and the leave would be pretty weak, even with the low gear 904.
With 3.55s you might run out of rpm.
3.23s make a nice compromise ratio for street use.
How much stall speed are you planning? I think your converter choice might be even more critical than the gearset.

 

[33IMP]

Low 8s eighth should be around 90 mph (maybe a bit less. )
5500 in second with 3.23s gets you 90 mph.

 

[AJ/FormS]

Oh you want realworld?
How about 93@7.92 in Second-over with 3.55s and a manual trans, on BFG D/Rs
The math says 6157 rpm.
The tach said 7000.
I guess that would be 13.7% tireslip, lol.

A track official came running over to tell me that my tires were still hazing thru the traps, and that I should lower the pressure.
I told him his airport-track was lousy.
I parked the car and went for a trackfood lunch.
The 60ft was 2.2 and change. It was indeed a lousy track.

My roadgear with 27s corrected to 28 was 5.13.
Yours with 3.23s is 4.97, also for 28s, but not corrected for convertor slip.

yur gunna kill it!