Ok, well, this is sort of an update on the propane truck. Much tweaking of the fuel system, carb, timing curves, etc, and still have headers left to put on to breath better, and re-doing my cold air intake ( cleanable air filter developed holes in it...) and then I should be mostly done.

According to mph in the 1/8 mile, I have somewhere between 108 and 115 hp at the flywheel, depending on the calculator used.

The truck is 10.5:1 CR, has oversize valves, a 260i / 248 e, 430 lift cam, super six intake, CA200 propane carb (2bbl throttle body).

I still have the stock exhaust manifold, no cat, and it flows pretty well.

Left to go is some long tube headers ( dual exh), and cold air intake. I limit RPM to 4000, and in my speed test runs, I shift more like 3750-3800 out of second. In the 1/8, I'm nowhere near getting out of 2nd, which would be low 50's.

What do you think is a realistic flywheel HP I should get by this method? This isn't a contest, the purpose for this is to have clues as to whether I should keep looking for things that are not optimal, or whether I'm close to what I can realistically get. Remember, this is a 4x4 truck, quite a bit of friction loss in the drivetrain, so I likely have a little more hp than the calculators say.

Any input appreciated.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

I don't know where my dyno sheet is. My stock cammed Duster peaked at 4000-4200.

HP at the wheels was 98 over jetted beyond belief.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

I've seen dyno charts that insist that a stock 225 should be able to make 120 at the flywheel, with the alternator, water pump, and exhaust in place. The propane system won't make as much power as gas will, but realistically, I don't know what I should be able to expect, given the mods and limitations. I suspect, given the rpm limitations I've imposed, and the mods in place, including the CAI and headers, that I should be able to get about 135 to 145 flywheel hp. Frankly, I don't care what the engine does above 3800, I'm never going to use it. I need power the most at 1800 to 3600.

Presuming a 10% drivetrain loss (manual trans), the calculator says just over 100 hp at the wheels. I hope late this summer or in the fall sometime, to actually get some chassis dyno time to fine tune the carb and timing curves. But I need to get everything else sorted out and as good as possible before then.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

You are in uncharted territory. I would bet with the truck you are more like 20 % drivetrain loss. With those same parts on gas, I'd say 150-180 net HP should be easy.

Lou

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Home of Slant6-powered fun machines since 1988

When Columbus fired up his Magellan, that's what it said...

I figured all of the Slant 6 world had been explored.

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'81 W150 on Propane... Oversize valves, Oregon Camshaft cam, 10:5 static CR, Distributorless ignition, megajolt timing controller, PowerTrax lockers.

No, each one of us is on a tangent and learning curve with our build whether stocker, mild street, or dual turbo EFI...

I tend to think of it as a learning journey rather than a means to an end.



-D.Idiot