The regulations in Australia require the propane flow is shut off when the engine isn't running, so we use a "safety" switch that shuts off power to the solinoid when there is no output at the coil

Same function, different method

Mark

 

I am finding this thread very informative. I have been doing some reading and I it looks like skipping dual fuel and setting up to run on propane solves the lower fuel mileage and reduced power cons. Bump the compression ration up to 12:1 or so and set the timing for propane. What are you using for a fuel tank? I found a few but they look pretty expensive.

 

I have a friend that does RV repair and has a few saddle tanks im planning on useing 2 of them.. they mount on the frame rail between the frame rail and the rear quarter panel.. All Id see once install would be the bottam where the fill and gauges are.. Im planning on duel fuel becouse this area is wide spead and Id like to be able to still run gas if I couldnt get propane for some reason.. Like on a weekend or in the middle of nowhere where there only gas stations...

 

Any chance of you asking him if he has any secondhand Impco 425?
My friends and I always have trouble finding them here
I have 3 guys on the Aussie Hot Rod forum looking for them, and I need a couple myself.
I am bidding on some on ebay, but lately there has been a lot of interest.....the gas crunch must be bitting ??

As mentioned above I tend to limit compression to about 11:1. Even though it is high octane it still detonates at higher compressions.

In Australia "LPG" is a mixture of multiple gasses and they vary the mix based on the time of year. I think they vary the % of butane.

Cars seem to detonate in winter, not in summer.....which makes me think the mix variations affect the resistance to detonation.

In the states they may have a different gas mix and/or may not vary it, so your propane may stand higher compressions.

In Australia I always use tanks from a company called APA. New they are $500+, but I get them second hand for under a $100. They are certified for ten years, but you can re-certify them for about a $100.

That's no use to you as they are way too heavy to ship, and unless they were new I don't think your customs would like their nature....."could be a nasty nerve gas or something in there"

I would be interested to know the prices over there

Mark

 

thats one thing about propane, they run a lot cleaner....
i overhauled an old WD allis chalmers, and when we tore it all apart, the head was almost spotless, and even the block seemed to be that much nicer...no oily residue, etc....
went to a tractor pull once and saw a M farmall run on propane....it did real well that day and wasted just about everyone in its class......when it was idling, you could barely hear it, but u could smell off the exhaust that it was a propane---along with the big tank, regulator, etc......i guess ive never heard of anyone losing anything for hp if you do it right in the first place....like somebody said, just get it set to fire with the propane set up, and u should be just fine.....
never asked him how the tractor worked in the winter time.....like they say...hindsight is 20/20...
Darrell

 

Since were on the topic how well do the Impco carburetors work? I saw a few listed such as the 55 and 60.

 

Well from what I have read.. ( And I can miss understanding it) Is the impco is not for duel fuel apps.. half, If Im wrong let me know...

 

The Impco stuff can be used for either propane only or dual fuel.
Impco make a HUGE range of adapters to mate their mixers to whatever carby or intake you have.

Download their catalog from http://www.impco.ws/products/carburetion.htm
at the bottom of the page, in three parts

The ratings on Impco (55, 100, 300 etc) are the approximate HP they can keep propane up to. So a single 55 or 60 MAY be a bit small for a Six
I say MAY because I see plenty of Big Blocks running quite happy with a single 425.

As an example my everyday transport is a Ford Fairlane with the late model Injected 5.0 litre (302) Windsor set up dual fuel with an Impco 225 inserted in the middle of the air hose from the aircleaner to the throttle body.

A mate of mine has the same setup on his 5.0 Holden (GM division in Australia)

For years I have been contemplating doing a Tri-Power setup using 3 55's on an edelbrock SBC manifold I have laying around. A 55 flows about 115 cfm so 3 of them should be OK for a mild 350

Problem is, I have NEVER seen a 55 here in Australia. I think they are mainly used on agricultural stationary engines in the states.

If anyone finds 3 secondhand ones give me a yell

 

They work GREAT.

I have found they are the best mixers on the market. Most of the other brands are cheap quality or a pain to setup.....or both

Most Impco's will fire up out of the box can be tuned by ear in 10 mins. Other brands won't even fire up until you have calibrated them on a flow bench.

See my other post re HP rating

Dual fuel on a Ford six I would go for a 125 on an adapter off the top of the carby.

 

I drop them a E. lets see what they say

 

See if you can get the full catalog with pictures ...... the online one is a bit uninformative.

Tell them you do marine propane conversions and are thinking of switching to there products

Speaking of marine. A friend of mine had a ski boat with an inboard 350 and 2 stage jet on propane.

We could ski all weekend on $30 of propane.

Other skiiers would come down the river for an afternoon and would handover $20 for "petrol money".........we got to ski and drink for free and make a profit

 

Sounds like fun..

 

If I did the conversion it would not be dual fuel. It would be straight propane.

 

So here's a follow-up question; how should a propane-only engine be tuned?

Sounds like 11.5:1 compression is part of it. How about spark and cam timing?

I'd think that you might want a 'short' cam (low overlap) with a pretty good LSA, 112?, and to set it up slightly advanced to get maximum low-end torque.

I'll bet the requirements for spark are easier than for a gasoline engine. I'll bet you can use a pretty small gap and a pretty low coil voltage and it would work fine. That would help the plugs last forever.

And what about pistons and rings? Hypereutectic pistons, for sure. Zero-gap rings?

Thermostat, 195?

 

I just build the engine like normal. Whatever you would do for unleaded. Don't NEED stelite seats in the heads, but if they need relacing you may as well

Because of the slow burn rate it can handle a Cam with a bit of duration.....I normally use RV type cams

A strong spark is important, again because of the slow burn rate, I always use an electronic ignition and the best leads I can afford. Any old coil will do

I will get back to you on the ignition timing and advance curve stuff. A friend of mine does the tune up stuff on my cars and I am stuffed if I know what ignition timing he sets it too

Mark