How Much Horsepower Required to Cruise Comfortably at 70 MPH?

dibbons said

I had a 1970 Porsche with a fuel injected 1.7 liter VW motor (factory). The 5 speed had two overdrives (4th and 5th). I could not use 5th gear on the highway unless I was cruising at least 70 MPH because at lower rpm's it lacked the necessary horsepower/torque.

So I am thinking too far ahead with the 340 switch evidently (apples to oranges?).

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Put an OD trans behind that 340 and have the best of all worlds.:D
You can still have low gears for the streets AND be able to cruise 70 like it's a breeze.
The 42 and 46 RH transmissions have a lower first gear anyway, and the 42 takes only minor mods to go in place of a 904.

I have yet to find a grade I couldn't easily pull at 90+ mph in OD with 273 rear gears.
In OD at 85 I'm right at 2,400 rpm's and then 2,100 when the converter locks.
You get WAY better mpg with the lower R's also.