so if I rebuild a 4.3 vortec for a swap and plan to use propane ONLY... what would be the optimum compression ratio ? cam? shaved heads? polished/ported heads?

A dedicated 'pane motor likes 11 to 12 to 1 compression. The same power tricks for gas apply (manifold, headers, cams,etc...) just can handle more comp 'cause the high octane. Race gas at $1.50 a gallon :grinpimp:

What he said....

I got mine to 10.5:1, works good.

As much as I advocate propane burning, why not just do the fuel injection for the 4.3?
Just FYI, I originally did EFI, I like the simplicity of the pane.

Oh, and as far as a cam, the propane doesn't really care, the timing is where it makes the difference. however, It's best to keep the power on the lower RPM. you can look up the info on the different cams to see where they are more efficient.

As much as I advocate propane burning, why not just do the fuel injection for the 4.3?


Just FYI, I originally did EFI, I like the simplicity of the pane.

Ditto...don't see that point for a dedicated trail rig... I may occasionally drive it to the movies or take the kid to the park on the weekend... but it's not gonna be a daily driver... it's being built for the trails..



thanks for the numbers... now I just gotta find an older vortec and get started... :D

Ditto...don't see that point for a dedicated trail rig... I may occasionally drive it to the movies or take the kid to the park on the weekend... but it's not gonna be a daily driver... it's being built for the trails..



thanks for the numbers... now I just gotta find an older vortec and get started... :D

Just FYI, the newer (96+ up) 4.3's had much better cylinder heads than the previous generations. The rest of the motor is different as well, but the cylinder head was the biggest change. Different intake bolt pattern, but the exhaust bolt pattern is the same.

well.. after pricing hoses and tanks today... I may just stick with efi.. still looking tho'.... is $15 a foot the normal rate... seems like everything around here is inflated... like 1 3/4 .120 DOM... $9 a ft...

i wonder how much per foot the painless wiring harness your talking about buying figures out to be.......