Cam? running Propane

[Bronco Buster]

A friend of mine has acquired a 350 Short block that has high compression (12.5) pistons already installed. He has propane setup (single 425) to run on it already. The guy he got the motor from kept the cam (that was part of the deal). He has vacuum power brakes. We are trying to figure a good size cam that will still have plenty of vacuum and pull from around 1800 to about 5500 rpms. None of the cam calculators I have found show propane as a fuel option. This is going in a cab truck with a 350 turbo, 1.97 to 1 case and 4.88 gears and 44's.
Do you run the same cam with gas as with pane? Do you use a bigger or smaller grind?

 

[Elliott]

Get an extreme 4x4 cam for it.if you will stay around a 270-280 duration cam it will scream.a smaller cam like that will save your brakes and keep cylinder pressure up.and you will not have to run a big stall

 

[doctordick]

TROOF !!

 

[Bronco Buster]

Thanks Elliott that is actually about the grind we were looking at but an Engle instead of Comp.