Author Topic: Little guy 1/8 mile RPM  (Read 4593 times)

Offline retroboy

  • Full Member
  • ***
  • Posts: 221
    • View Profile
  • Your Track: Whyalla
  • Your Vehicle: FED
Little guy 1/8 mile RPM
« 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

Offline George

  • Hero Member
  • *****
  • Posts: 518
    • View Profile
  • Your Vehicle: 1964 Mercury Comet Super Stock/ M automatic
  • General Location: Midwest USA
Re: Little guy 1/8 mile RPM
« Reply #1 on: April 19, 2015, 05:49:36 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

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

Plug in some numbers and away you go. George

Offline retroboy

  • Full Member
  • ***
  • Posts: 221
    • View Profile
  • Your Track: Whyalla
  • Your Vehicle: FED
Re: Little guy 1/8 mile RPM
« Reply #2 on: April 19, 2015, 06:36:16 PM »
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

Offline JrFuel Hayden

  • Hero Member
  • *****
  • Posts: 600
    • View Profile
    • Hayden Enterprises Speciality Wheels
  • Your Best Time: 6.02, 236 mph, 1/4 in 1973 Div 3 TF Champ
  • Your Engine: SBC, Alky, 403 ci, Best 6.99 @ 190 & 409 Hemi
  • Your Track: Bakersfield
  • Your Vehicle: 225" FED NHRA Heritage Jr Fuel
Re: Little guy 1/8 mile RPM
« Reply #3 on: April 19, 2015, 09:22:33 PM »
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
Jon C. Hansen

Hayden Wheels