MPG Motor Magnum vs. Hemi
MPG is calculated the same as with gasoline... Liquid propane tanked versus miles driven.
I've got a phone-app which I use to keep track of the mileage for over a number of years now.
Great (or not) to see mileage rise or (usually) drop based on outside temp differences or (sometimes) changes on the car.
I'm kinda blaming the transmission (A518) and the perhaps in-efficient / old design(?) '60s stall convertor (non-lockup) I've used in it for the crappy mileage the car is getting.
I think I'd blame that camshaft.Specs are 256/268/110.
It's only got 42* of overlap, but in your application, at up to 1800 or maybe as high as 2000 rpm, a lot of that propane could be scooting straight across the top of the piston and out the back door.And with your gears, 65~1980 rpm at zero slip; right at the top of the crap-zone. You might want to think in terms of less overlap.
A little smaller cam on a 114LSA would have about the same compression /power durations, but the overlap could be reduced to say 25 from 42 . Yes you would lose a bit of absolute power at higher rpms,but you would gain a fatter powerband to pull those wide automatic ratios, and so I doubt your average power would change much.
Here's a theoretical cam worth perusing:
int....comp....pwr...exh....o/lap...in at
256....126.....118....268...42......106........... your current cam
250....122.....117....256...25..... 113........... replacement cam
There are others
I'm just trying to be helpful, and
Just something to think about.