70 percent of full load rpm. 5400 x .70= 3780. We use 3500 rpm

Don't remember what power you were upgrading to but I'd be shooting for low 60's in the 32-3400 range for an economical cruise.

I dont think the motor will be in the rite tourq range at that low rpm .

find out where max tourq is and that will be the ideal rpm range to cruise at . most big block's seem to be around the 4000 mark give or take a few hundred rpm

The stock motor was a 502 mag efi (415 hp). The new motor is a 509 with a b&m 250, cam, mild ported heads (088) and roller rockers. I've read similar builds having 650-675hp, but that's what I've read so time will tell.

What Prop pitch (1) and Drive Ratio (2) are you going to use?

Then, Cruise RPM x (1) / (2) / 1056 ( I use 1056 cause it usually gets me very close without having to calculate slip )

that formula will get you real close to your real world #'s

That's a cool formula. I had to use 1150 vs 1056 to get my numbers right. I cruise at 3500 at 65mph GPS running a 32P Bravo 1 (stock).

Install 1:36 gears and toss the 1:50's. You will cruise a lot faster turning a much lower RPM then a 1:50 with a higher top speed. The 1:36 gears are also stronger then 1:50's





































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If he switches to 1.36's then he has to decrease prop pitch by 3" or so to get the correct WOT rpm range.
1.36's spinning a 26" prop and 1.50's spinning 29" prop will still yield the same cruise and wot speeds within a couple mph.
1.36 gears might be just a tad stronger, but nothing huge.

do you know for a fact that the 1.36 gears are stronger than the 1.5's? i thought it was the other way around because i thought the 1.5 gears were slightly bigger. not sure tho
help mr gadgets????

Yes, the 1:36's are slightly larger. Correct, he will have to decrease pitch to get his his desired RPM. 1:36's are like starting off in second gear in a car, once you put it in gear you are moving at just idle! So right out of the gate you already are are up on a 1:50 operator. top end is also good for 3 to 4mph