Inliners International Forums General Discussion Engines Timing on 250 with LPG

Hello all,

I have a Chevy Van with a 25 6-inliner engine.
It is running on LPG but to my opinion it delivers not much power.
I am thinking that the ignition isn't in time.

Can anyone help me?

Frank

Frank, I've had several vehicles on LP gas. They will pull harder and generally have more low-end torque, but never seem to have the power at highway speeds. However, you can advance your timing several degrees from stock. One way to do it, without a dynometer, is to advance your timing a degree, or two, then drive it. I like to take my vehicles out for a timed run. If that goes well, do it again, until you see no improvement in performance. I usually retard the ignition one degree afterwards, just to be safe. Worked for me!

Well Lammy I've had some experence and triumphs with lpg so lets try. I assume you have just done the conversion and are disapointed with results. Lpg has more octane but less btu's than gas so what is happening is not unusual. Dennis is right dial in as much advance as motor will take and take a little out. LPG doesn't need exhaust heat so maybe make a stainless sheetmetal blockoff plate for exhaust and intake. LPG likes a different advance curve than gas ,pull some out at top end kind of like a blower motor.If you plan on using LPG only I would suggest high compression about 12 to 1 and a hei with a hot aftermarket coil. Hard seats, bronze guides and hard valves may be a good idea if you plan on runing hard. My dad and I expermented on a 70's chevy 4 wheel drive pickup. On gas with a 250 6 the best economy we could get was 10mpg. With a 350 v8 and the mods suggested above we got 25 mpg and proformance was improved as well!