Tires or Gears
 

Looking for some racer input.
Running a SBC 401 stroked 3.750 with 6" rod, 4.88 rear, 1.80 glide, 14/31 rear tire rolls out 98-99". Motor Dyno shows peak HP at 7100 rpm. Shift on time SST trim 2830 lbs.Currently going through traps 8K. I would like to drop the trap RPM to around 7600-7700. I need new tires so I believe my options are go to a 14/32 tire rolls out 102", or change gear to 4.56. What would you suggest?

Re: Tires or Gears
 

Tire for the first change.
If you change gear ratio it might upset it too much and you might have to end up with a 1.96 low gear in the tranny. Expensive changes. The gear is about a 7% change. 8,000 - 7% = 7,440
1.80 x 4.88 = 8.78 1.80 x 4.56 = 8.20
That is 7% diff in overall low gear.
See the 7% goes all the way back up the power train. It might even upset the stall or hit on your converter

Re: Tires or Gears
 

Drew , if I remember correctly your current tires are only. 100" roll out .
I think the 104" tires will drop you 300 rpm from my experience .
You might get away on the .500 tree with the 4.56 gears , your car hits the tree pretty hard with the setup you have now , and you can drop the delay a little .
Give me a call this week .

Re: Tires or Gears
 

Thanks Guys for the advise and suggestions.
Tom, I will give you a call.

Re: Tires or Gears
 

Just dont touch that ET transmission! E

Re: Tires or Gears
 

E Man,
Don't worry I won't touch it.
The "ET" tranny is working flawlessly as always!!
Thanks for a great Job.!