Been lurking for a while...and I gotta say, as far as forums go, you folks are pretty tight knit. Very nice to see. Since my build won't be started for at least a year (81 Monte Carlo Turbo), and until today I've had nothing to contribute, I've held off on posting. This might be a little long, but I ingested quite a bit on the subject. That said, let's talk some Propane.
A thread in another forum I frequent got the juices flowing , and I've spent most of my day off researching Propane fueled vehicles. The info I found has me pretty stoked at the possibilities for this community. Just to clarify, were talking about Propane/LPG (Liquified propane Gas).
Okay, The facts: Propane has a comparable Octane rating around 110 (excited yet?), cost varies widely depending on region/state...U-Haul has it for $2.98 per Gallon in town, Federal and/or State tax breaks offered for converted vehicles, Lower emissions across the board when calibrated correctly, Longer engine life, Oil change intervals extended to 13K+ on N/A engine, Zero carbon build-up, lower intake charge temp, and engines have been reported to run much cooler.
The retrofit kits come in two varieties: Duel Fuel and full Propane. The Duel Fuel kit lets you switch between petrol and propane via switch. It retains the factory carburetor with a "plate" above it to disperse the Gas. The full propane conversion replaces the Factory Carb with a "Propane Carburetor" which bolts up the exact same way as a carb, but from what the off road forums say, is infinitely quicker and easier to tune and rebuild (minutes, not hours). Given the octane differences of the fuels, 91/93 Vs. 110, the off road guys run their rigs at 10:1, 12:1, 14:1 +, and can add quite a bit more advance. Whats the CR of our 3.8's...8, 8.5:1? I'm still trying to wrap my head around it all, surely don't have it all down. Vacum EFE/EFE II system on 78-80 would definitely need to be disconnected, and the Electric EFE/EFE II on 81-83's... I don't know.
From all I've found today, Draw thru Turbo's were made for Propane...and the off-road community has paved the way. One possible negative I've read about is with exhaust valves and the need for hardened valve seats. I've seen no examples today on it happening to modern engines (modern= Un-Leaded fuel), but it was mentioned several times in forums. I have no idea what ours are made of, someone can chime in? It's a bit of reading, but this looks to be a way to have the built in results water/methanol injection offers, but without the ancillary system. There are several other topics and theories I'm itching to discuss with you guys, but I'll hold off...one thing at a time lol.
Draw thru propane info
Compression for Propane w/ turbo
Propane 101 from an off-roader
General Valve Seat article:
Propane conversion FAQ from a merchant
C/R for propane. detailed discussion on propane theory from people way smarter than me.
I've bounced back and forth between three different directions for the build: (what most of you have done) modifying the as-is factory system with carb/head/intake porting, cam, and turbo mods....A Megasquirt for ignition and knock sensing w/ factory Rochester....or a Megasquirt with TBI. Looks like there is now a viable 4th option!
What do you guys think? Any and all opinions/thoughts/comments wanted
Edited for to make factual correction.