Propane and Hi-Performance?

[TerryD]

A while back I posted a question here regarding the pros and cons of a dual-fuel propane conversion. I got some good info, so thankyou.

I'm wondering if anyone out there has experience, or knows of someone with experience in setting up an engine for both propane and high performance. I have a '94 GMC 2500 4x4 with a pre-Vortec 350, and I'd like to modify it to get between 380 and 400 hp. I plan to do it right, and set up the whole engine for hi-po, not just change a few things. I've heard that propane likes hi compression. Is that right? And are there any specifics I have to consider because of the propane? For example, if propane likes, say, 13:1 compression, and I have the truck on dual fuel, how do I get it to run properly on gas?

Any info would be appreciated. Thanks!

[cayoterun]

I restored a '58 Chev Imp a few years ago. Used a 454 with 10.5 comp ratio/w 4 barrel carb. This engine was only a 450-475 hp (est. by machine shop, never dyno'd). It run and performed great. It was only a "show and tell" car and made a great conversation piece. Cost, economics, and availablity wasn't a factor as I already had the conversion on hand.
But, if I planned to build a real hot engine as you are and use it on a regular basis, I think I'd just stick with gas. I don't think it would ever be worth the added cost.

I checked a few months ago with our fuel supplier about a conversion for our '97 454 and he told me they hadn't come up with a real compatible set-up for the newer electronics and fuel injection as a add on system. They work fine with carbureated engines.
The factory equipted systems seem fine for commercial use.
Just my .02 and I'm really out of touch with the newer technology tho.
Looking forward to others imput and what you decide.
Keep us posted.
Cayoterun

[TerryD]

Thanks for the response. The reason I'm going dual fuel is because propane is half the cost of gas here in northern Alberta. I'm currently getting about 11 mpg, so a $3000 conversion will take only about 1 1/2 years to pay for. I use the truck everyday for work (construction), and I figured if I'm going to build a hi-po engine, I might as well use it in my daily driver. Besides, I need at least some of that power for pulling trailers, hauling equipment, etc. I just thought I'd do some research on the specifics of propane and higher horsepower. Thanks!

[68gmcdually]

We have a '93 K1500 on dual fuel, it is a real dog running on LPG towing a trailer but great on unleaded. Normal day to day driving is fine on LPG as well. Mind you we haven't tweaked the motor, it is stock.

[cayoterun]

Wish we were closer, I have a full conversion, 60gal tank and all, I'd loan you for a trial, but plan to use it on the V-12 truck later.
Since yours has a carb, it probably would work real well. Run on gas with heavy load, propane normal driving as 68gmcdually said.
Cayoterun

[ChevLoRay]

The people who should know the answer you seek are at the gas company that sells propane, aren't they? If they do the conversions, there has to be someone who has first-hand knowledge of the possibilities.

[Scott68-93-97]

Run Propane only and build a high compession motor to get the performance. At the optimal comp ratio propane will get more power on a lesser mixture than gas but building a dual fuel vehicle you can't get the performance out of the propane at the comp ratio that pump gas works at. Propane runs a 16:1 air/fuel when at the correct comp ratio, There was a chevelle they built on hot rod tv that got over 1000 hp on a natural aspirated propane engine. Burned clean and better mileage. When you lower the comp the propane needs a higher mixture to light wasting more fuel. This is the same problem with the ethonal/gas vehicles at a gas comp ratio your not optimizing the power of the ethonal and you actually get worse milage running that. My brother drives a truck for shwans foods and it has a chevy 6500 w/ a 8100 vortec LPG only motor and it hauls some serious a** loaded down with food. But its propane only comp ratio is too high for gas, it also gets 20mpg weighing in at 14,000 gvw unloaded ( big freezer on back )

[TerryD]

Thanks, Scott. That's good information. I think I'd be tempted to go propane only, except here in northern Alberta, the winter temp often gets down to -35 or -40 Celcius (-40 is the same as for F). Propane tends to gel at those temps, and doesn't start well, even in less extreme temps. But that's the kind of info I need. Thanks again!