High compression V392

[lil acco]

Hello from australia, I have a light medium truck with a v392 early cooling type engine. In wish to run it on lpg propane instead of gasoline. My questions are 1. What is the best way to raise the compression ratio to about 12.5:1.?
2. Would the cylinder head gasket stand up to the higher comp ratio?
I have been running a locally produced 308 cu in v8 ( similar to a sbc Chevy) on lpg for years and know of all the problems with it. I am after an engine with grunt . The crank stroke on the holden 308 is only 3" and cannot give me "enuff chugg". I don't really want to have a high performance engine ie. A high revver, just something that will pull nicely up to about 3500 rpm max.

 

[Robert Kenney]

Pistons.. Even then they will be big intruder domes.
You'll need to evaluate the existing piston combustion chamber configuration. You May have a contoured dome 392 that has the big open chamber.

But either way, the only thing you can do to achieve 12.5-1 is with pistons.

Compression ratio is not the head gasket killer, heat and detonation are. Properly built tuned and fueled for the 12.5-1 your good as gold.

For me, I would run 7 pounds of forced induction and end at
12-1 effective cr.

 

[lil acco]

Rk thanks for response. I got a v345 I might swap head from. I see another post somewhere that claimed about 10:1 comp with 345 cyl heads on 392. I also saw somewhere that there are different piston dome shapes. Is this myth or factual? Maybe just engine development improvements. I am reluctant to pull heads just for a look as truck is still working for its keep. Imo my research revealed that engine needs much more than head skim and block decking to increase comp ratio. And the is some Ford flat top pistons that could be fitted (with machining alterations), but no indication of what comp ratio I would end up with. I wondered if IH made an industrial/ pump engine built to run propane was ever made. Cos parts from it would be worth considering. The boost idea is worth considering, but benefits would only be best at wide open throttle ( ideal for constant load ie. Pump). I was thinking of possibly using 2 turbo's (from 2.8 litre hilux or isuzu) might go well with 1 hung of the standard exhaust header flange (each side) and blow thru an impco 425 mixer with air box on top, but I am not ready for that challenge yet. I think it would be better to pipe exhaust to garret to3/4 mounted to area behind carb/mixer. Truck is coe so less unmanagable heat around engine. Thanks in advance pjs