I am doing some reseach on a lpg conversion for my 351w build... It is currently fuel injected and i would like to keep it fuel injected too... I understand for best results that compression should be about 14:1 does that sound accurate. Also do you have any advice on where to get parts for this or what companies could supply me with some more specific and detailed answers. For reference I was planning on building the motor stroking it to 408ci Then coverting to run on lpg since it would be built specifically to run lpg i wont have to worry about mixers... Any tips, expierences or advice would be much apprecieated.

Thanks,
Don

 

Please contact your local LP gas dealer for the equipment. Fuel injected engine are the best candidates for conversion however you will still need a "mixer" to introduce lp into the air intake. You might be able to find a plate mixer that would go between your Throttle Body and the intake but I would not recomend it for your built up engine as it will limit your flexibility in fuel volume. Also you will need a high intial advance but you need to limit the total to around 28-32 deg @ 3000-3500Rpm. Dual Curve (MSD) makes a unit that will do a nice job without having to recurve the distributor.
Let me know if I can help

Regards

 

The best way to convert an EFI engine is with a propane injection conversion. There are a number of these systems on the market but the lowest priced system is the ESIP parts package made by Technocarb.

The critical compression ratio for propane is about 12:1. For best reliability, keep the CR in the range of 10:1 - 11:1.

 

what about cam timing and lift. what recommendations can you make. I am thinkg of the same converstion, but for a carb'd 351M. I know about the timing advance, but what about reducing cam overlap from stock to keep dynamic CR up, and increasing lift to flow the same, or more, volumn whith shorter duration?

 

Propane is just another fuel. The type of cam you need depends on the intended use of your vehicle. If you want low RPM torque, you need to select components for this purpose.

 

hi, i have been running my truck, a 4,2 v6, on propane for a few years now. it has had no changes to cam or timming and uses a mixer. it runs well but if i want full power i have to switch over to petrol.
the injection propane is the way to go for full power but is more expensive and the system will posabley require a laptop to setup. bokker.

 

Franz Hofmann, Alternative Fuels

 

Go to Propane Conversion Kits They have kits built specifically for carbureted vehicles. You do need a 4v intake, but the propane unit replaces the carburetor completely(unless you choose the dual-fuel kit, which adapts to most any 4v carb). No worries about proper jetting or manual adjustments. You having a 351m works too. The 351m has detonation issues with CR's much over 9.5-10:1. Propane is 100-110 octane, so you can run higher CR. With these kits, you can run stock components, but in a 351m, why would you want to? No need to change much.

Carbureted propane vehicles have been used for quite a while now in off-road and rock crawler capacities. However, they do warn that, if your vehicle applies to your states' smog emission regulations, it may not be legal to run. I am in the process of installing a kit on my 400. In Utah, vehicles made '68 and up have to be emissions tested. Good thing my '73 400 is in a '67 f100. NO EMISSIONS TESTING!!! (though propane does run cleaner, still illegal)

 

a '78 in TX does not require testing either.

 

It's been years prior to '68 here for a LONG time..... They keep "talking" about moving it to later years, but here in northern Utah, we are cursed with living in one big valley. We have major smog problem as it is. During the winter, when we have no wind or storms push through, we have HORRIBLE inversions.

I need to move back to Florida or another coastal state that has less restrictive smog/ emissions regulations.

 

Yeah, those hurricanes tend to blow all the pollution elsewhere....




Steve