Yes, it was the '91 351, yes the propane got worse mileage on both trucks and runs hotter on both trucks. The 91 setup actually replaces the stock airbox with a round open-face K&N filter with the propane diffuser mounted in the lid, so the propane is released into the airstream right where the clean air sucks into the two big air intake hoses, so it mixes very well before entering the EFI intake.

 

Thanks for the explanation. From what you said, it doesn't sound like something I want to do to mine.

 

A mixer has a metering cone that is connected to a diaphgram. The diaphgram is raised or moved by air flow into the engine. On a dual fuel set-up there is a cable that connects to a "cam" on the mixer that when it is pulled raises the diapgram up and out of the airflow so you can run gasoline. If you do not open then mixer then the truck will run rich like a stuck choke. With the proper set-up a lp engine will basicly the same as gasoline. If not there will be as loss of power and mileage. LP is similar to hi-octane fuel (aprox 125octane) it needs a high inital advance and very little to no advance at higher rpm. Also lp being a vapor not an atomized liquid does not wash down the cylinder walls and dilute the oil and it burns cleaner and doesnt contaminate the oil. I have never run into an lp engine running hotter than gas if it was set up right

 

thats what i found to be missing from my setup, the cable to open the mixer, just one of the mistakes made on this setup.