Im to the point with my 69 runner drag car where i need to order rear gears n spool. I had the engine on the dyno last week and it made 642 hp at 7400 rpm and 536 ft at 5600 rpm. im guessing the car to weigh 3200 and running a dana and 33 x 16 slicks. Auto matic trans with a brake. I have looked at on line calculators and come up with 513 on gears. i have had local guys tell me to go with 488s. wat do you guys think?

Don't forget about converter slip. Usually 4-5% for a good one.

7400 x .95 x 33" / 336 / 4.88 = 141.48 MPH

7400 x .95 x 33" / 336 / 5.13 = 134.59 MPH

640 HP in 3200 lbs should run 136.5 MPH

Just a little math for you to ponder......no recommendation.

The first numbers that came into my head after looking at your post was 4:56 Is this a power glide car or torqueflite trans? I think you need to ask some of the Powerglide racers what gears, tire sizes and shift points and car wieght and engine combinations they use and go from there

ok from what im seeing in the math here the 513 looks to be bout right? This is a 727 with a brake. engine is a .060 over 440 with weisco flat tops indy -1s, non ported, 680 ultradine roller and a 1050 dominator. im looking to run in the 130mph neighborhood.

With the stock stroke 440 the lower gears(4.88) maybe better than the higher gears(4:56) I ran a 3700 lb car with a lesser motor than yours with 5:13 gears and a shorter tire(103 inch circumference) that ended up running a bunch better with 4:89 the converter will make the difference on what the car likes or don't like, a good converter makes a lot of difference on which rear gear is needed. A good converter will run fast with less gear than a loose converter will

I really appriciate the help. the convertor i am running is a dinamic 9 in and is set up to stall 49 to 51 which is tight for the torque. i had this motor in another car before freshening it up and was running 488s with 32 in tires. it has never 60 ft like i think it should. it was doing a best of 1.48 60 and 129mph at 10.35

I have 3400 lb street Duster that has a 518 C.I. low deck pump gas motor(718 HP at 5800 RPM, 745 ft. lbs at 4500 and 4600 RPM the last time on the engine dyno) that has ran 10:43 at 128.6 MPH cork up on Oregon pump gas, that car has a custom built (for this motor off of the dyno sheets) Continental 10 inch converter in it and has ran the same ET and MPH with 3:73, 3:91 abd 4:10 with a set of 30 inch tall M/T 315x60x15 ET Street Radials ( 30 inches tall, 98 inch circumference I think) at two different tracks I would put the 4:88 in your car

I,m with Cab on this, 4.88 gears with that tall slick ought to be about right.