Non-thirdgen propane timing
10-10-2002, 07:26 PM
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Non-thirdgen propane timing
Does anyone have an idea what the advance curve for a propane-powered 307 SBC should be?
10-10-2002, 09:58 PM
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Different truck... the Ford's a 444 Diesel, this one's a 307 Propane GMC.
10-11-2002, 03:49 PM
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Car: 1986 Sport Coupé
Engine: 305-4v
Transmission: 700R4 and TransGo2
All I can tell you is that we used the stock HEI timing curve in my 1979 Impala 350. It worked quite well.
However, if I recall correctly, the advance can be quickened somewhat. Propane has a higher octane rating, so try one step looser on the springs and then advance the timing until it pings, then retard it 2 degrees.
If that works well try the next set of looser springs, etc.
Just make sure the coil is a hot one. More octane equals harder to spark. I remember the day we converted mine over. Two plugs and two wires that worked fine on gas gave up the ghost instantly on propane
However, if I recall correctly, the advance can be quickened somewhat. Propane has a higher octane rating, so try one step looser on the springs and then advance the timing until it pings, then retard it 2 degrees.
If that works well try the next set of looser springs, etc.
Just make sure the coil is a hot one. More octane equals harder to spark. I remember the day we converted mine over. Two plugs and two wires that worked fine on gas gave up the ghost instantly on propane
Last edited by Sitting Bull; 10-11-2002 at 03:52 PM.
10-12-2002, 12:54 AM
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Yeah that's what I hear, propane is around 110 octane or so. I've got access to a good old fashioned distributor machine here too, so it's fun to play with timing. 
10-12-2002, 01:00 AM
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Car: 1986 Sport Coupé
Engine: 305-4v
Transmission: 700R4 and TransGo2
The nicest thing, IMHO, is that propane costs half what gas does and still gives you almost 90% of the mpg
I remember buying propane for .08 cents/gallon.
That was 20 gallons at 8 cents = $1.60 to fill the tank :hail:
For you Americans out there, that would be like filling your 20 gallon tank for $1.00 ... pretty hard to take, eh?
I remember buying propane for .08 cents/gallon.
That was 20 gallons at 8 cents = $1.60 to fill the tank :hail:
For you Americans out there, that would be like filling your 20 gallon tank for $1.00 ... pretty hard to take, eh?
Last edited by Sitting Bull; 10-12-2002 at 01:05 AM.
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