Drag Racing Discussions > Front Engine Dragsters

Little guy 1/8 mile RPM

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retroboy:
Howdy. I've just finished the rebuild of an old FED just in time for our Aussie winter so I stripped it this afternoon to get ready for paint and detail.
I have a 31" tyre, 4.3 gears and no trans brake so will leave around 3/3,500 RPM. I'm going to change to 4.56 gears. What RPM are you guys with similar set up's running on the top end of the eighth.
Cheers
Tony

George:

--- Quote from: retroboy on April 19, 2015, 03:56:28 AM ---Howdy. I've just finished the rebuild of an old FED just in time for our Aussie winter so I stripped it this afternoon to get ready for paint and detail.
I have a 31" tyre, 4.3 gears and no trans brake so will leave around 3/3,500 RPM. I'm going to change to 4.56 gears. What RPM are you guys with similar set up's running on the top end of the eighth.
Cheers
Tony

--- End quote ---

Lots of good calculators here. http://www.wallaceracing.com/Calculators.htm

Plug in some numbers and away you go. George

retroboy:
Thanks George I looked at there race simulator a while back and aI thought it read a bit high so I was just looking for a few "real world" results from any similar combos

JrFuel Hayden:
I just looked at my RacePak, with my 4.56 gear and 31x12x15 Goodyear D2585 on 12" wide wheels, my 1/8 mile ET was 4.488, 152.54 mph, and 8365 RPM, on another run my 1/8 ET was  4.463, @ 157 mph, and 8440 rpm. The difference is in the converter, and we were making more power when we ran 157mph. BTW that run was 7.029 1/4, @ 187.52 mph, racing our Hemi in JrFuel Heritage.

I hope this "real world numbers" helps you. One thing to keep in mind is the D2585's will grow more when on 10" rims than 12" rims.
I have been asked about tire growth, but my Computer confirms the on-line calculations on gear-tire dia-mph-rpm, because the tire growth seems to cancel-out with the converter slip. Just trust the math. 

Jon

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