Engine RPMs

[jkindt]

After getting the bus out on the highway with the new tachometer installed I was able to figure out the cruising RPMs. At 100 km/h (as per GPS, speedo is still broken) the engine is turning 3500 rpms. Anyone know what the optimum cruising rpms would be for the Ford 370's? I have found that first gear is pretty much useless and the second through fourth seem to be quite close in ratio, but the jump from fourth gear to fifth is quite wide. If I shift at 4000 rpm from fourth to fifth gear I end up lugging along at 2500 rpm. Also, any idea what the redline is on this engine? Can I spin it faster than 4000 rpm without blowing it up? It sure seems like it is screaming at that speed.

[crazycal]

Man, that's screaming. I can't imagine your fuel economy is that great at 3500rpm. I bet you pick up a couple of mpg if you dropped the rpm's by a thousand.

[jkindt]

Originally Posted by crazycal

...Man, that's screaming. I can't imagine your fuel economy is that great at 3500rpm. I bet you pick up a couple of mpg if you dropped the rpm's by a thousand.

I figure I get about 6 mpg or so...haven't had it long enough to get an accurate estimate. Also, it is on propane so the tank is never filled to exactly the same level from one fillup to the next due to many variables.

[Iceman_biker]

I wouldn't turn that motor much over about 2000-3000 rpm. That is a long stroke small bore motor, they don't like to spin fast.