Higher compression for my 70 Chevy c10 307
I have a 70 c10 307 chevy that has used propane since 1988. Propane has 108 octane, thus the 307 low compression ratio is not optimizing mpg. I purchased the truck 4 months ago, have a 4:10 ? gear ratio at present and no overdrive. I am presently achieving around 15 mpg combined village and hiway driving. I plan to change the rear end ratio to 3:08 and will probable be getting around 16-17 mpg on the same roads. 15" wheels, stock tire size.
It needs a valve job at 140,000 miles I am aware of the need for hardened valves for the propane combustion. I am interested in the options that I can build into this engine to increase the comp ratio. I am aware of a threshold where the propane fuel will auto ignite due to high compression. What is that point and what is practical as I consider all that can optimize the propane fuel.
I am paying $2.25 per gallon at present. That calcs my actual cost per mile in the 28-30 mpg range. I am hesitant to discuss this as big brother will certainly tax the hell out of propane if it becomes more popular.