Hi, guys. I'm newly registered here, but I've been lurking and reading old posts for several months. I was hoping to get some expert opinions on my up-coming project.

A bit of background: I'm building a WORK truck, not a race car. I've got most of my pieces together, but I'm not positive on what turbo to use. The chassis is a 1974 Ford F-250 dually. The FE engine it has is bad, but it has a good NP435 4 speed in it. I've bought a '92 300 to put in it. The plan is to run it on straight propane; it won't even have a gasoline tank mounted. I ranch for a living and most of my time is spent idling around at low speed. I do want the ability to do some moderate highway hauling with the rig. For heavy-hauling I've got a '76 Crew Cab 460. This truck will normally be carrying about 800 lbs of tools. In winter when I'm feeding cattle I'll have about another 3/4 ton of feed loaded on as well.

I've read a couple of books on turbocharging, including Jay K. Miller's Turbo. I've also trolled ump-teen internet sites doing research.

My goal is to keep this as simple, cheap and reliable as possible. I'd like decent fuel mileage (high teens on highway, I hope) with plenty of torque. My idea was to slightly undersize the turbo for the engine with the theory that it would start making boost at a lower RPM. I'm only wanting to go 8-10 lbs. Fuel system is an Impco 435 mixer and related parts.

I've been leaning toward something like a GT 2860RS or possibly a T-3 series Super 60. Am I on the right track here, or have I misunderstood some of the calculations?

 

Cool project but one that will be tough for most of us to answer. Boost at lower Rpm means massive low end and corresponding cylinder pressures. This would be a real problem running gasoline but may not be on propane, I'm not sure where the limits are

Wrt sizing- airflow = hp. Hp / rpm is proportionate to torque. Its not really this simple but if u size the turbo for the maximum hp ur looking for u should get pretty close. But remember that allwer turbos make for touchier engine combinations. MOst t3s are all done before or just over 300hp.

 

Sorry, in my long rambling post I forgot to mention that I'm looking for peak HP of about 300-325, between 400-450 lb/ft of torque. I'm not looking to break any records. The goal is to approximate or slightly surpass 460 performance numbers with hope of better mileage than a 460 gets.

The engine I have is an EFI 300. I'm planning on stripping all the EFI components off it, and mounting the propane mixer where the throttle body mounts. From my research the long intake runners should aid in getting the torque in the lower RPM range I won't have to worry about fuel dropping out because propane is a gas already. The engine also has the dual exhaust manifolds (two three-into-one). I had planned on fabbing a pipe to connect them and running the turbo off that. Supposedly the dual manifolds also contribute to lower RPM torque.

 

S300 66mm ?? .88 A.R T04 ??

 

The 300 six has a weak head gasket , try with copper gaskets , o-ring and head studs just would push coolant out the overflow . Was propane OHG blowthough ,about anything over 10# boost it would push coolant. The fix was told less timing or 1/2 head studs . found aguy that did 1/2 " studs took 3 blocks to get a good one , not much meat in the block for larger studs and it crack a year later . Wanted max power so 8# was not going to work for me . 78 x-cab mud truck 12# felt great , swap a 351w at 15# no problems . Motor does have limits , ford did make a svo block but just a few , lots of info on 300 six .

 

Welcome man. Cool project! I love things like this.

There is only one thing that I see your not even going to come close to meeting and that is fuel mileage. Propane is way down on BTU's so your fuel mileage is going to be the same. One thing that you can do to help that is jack the compression up because as you know, propane has a high octane value.

Another thing you might want to think about is power. Every propane engine I have been around has been down on power from what they should be. I used to race against a guy that had a propane powered Henry J. Nice car and super nice engine. We would wax him with our junk stuff. I have no doubt if his engine was on gasoline he would have made big power. Knew another guy that had a twin turbo SBC on propane. Same thing with that engine. It just did not make the power is would have on gasoline.

So jack your power level up from what you think it should be. Anyway, good luck, sounds fun.

 

Running Impco vaporizers? I've heard past 7 or 8 PSI the covers start to flex on them. Just a heads up.

 

Similar, but different is my work truck, daily driven, 302 straight propane non intercooled manual trans.
Used a 64mm s400 T6 1.1 Hotside
Boost from 2k full boost (10psi) just under 3k
Full load and tractor on the trailer behind (3.5 ton) and pulls like a train.
Cab over tray truck

 

my friend tow truck 6cyl ford 300 , 2 barrel 32/36 Weber Carb , turbo from Mack diesel engine

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