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Discussion Starter · #1 ·
On my 94 S10 with a FB4001A motor, I am trying to figure out the max RPM’s without damaging the motor. The reason is to get the max MPH on Interstate grades and not irritating the guy/semi behind me.
So spent a few hours tying to figure out the ratios to avoid buying an rpm tach, plus heard some aren’t too great anyway. So I jacked up 1 tire and spun the motor. I know the figures I got are wrong (5.5 motor rev per 1 tire rev in first). Guess both tires must be moving to be accurate.
What I know:
1- 2800-4500 RPM is max efficiency per a performance chart. Previous owner said to run it at 3-4K. Agreement here.
2- calculator says 60MPH @ 4211 in 2nd, 2586 in 3rd for a normal rear end. Mine was a factory special order 2.56 ratio. That is at least 10% fewer turns of the shaft, right? Safe to do 60 in 2nd since 3rd bogs down to much?

What speeds do you safely use?

1994 S10 120v US145 Batt
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