I'm looking for some help on selecting the right valves and springs to put in a stock 350 engine. The guy the is selling the motor say's the engine is good but his fuel milage has dropped off in the past 20000 miles. He has been told by many mechanic the propane engine are hard on heads because they run hotter than gas motors and he has 240000km on the motor. I need to know if the heads can effect the milage that much and what is the best combination in parts for rebuilding the heads should I go with? I want power yet good milage too, the motor is a duel fuel if that matters. I will be putting this motor in a 1985 chev. 4x4 with a 700r4 not sure what rear end ratio it has but there is a 6.2l in it now. Thanks for any help
the real story: First propane DOES NOT RUN HOTTER its BTU is less than gas. But its Octane is about 125. You can use a stock engine to run on propane. Two. You will get about 1 mile less a gal on propane than gas on a duel fuel engine and about 10% less power. MOST IMPORTANT MAKE A NOTE: you must break in the new engine on GAS first to set all the parts in if you do not it will take about 40000 miles on propane becouse it to clean. I have a 1980 crew cab that is a duel fuel and can tell you all you need to know about propane. If you want power you would need to have a 12/1 you can"t then run on gas only propane If you need more info leave a post on this page I will check back I live in Cal about the rear end check the tire size and look at a table it will tell you the rear end for that tire size stay at freeway speed the best.
