I want to supercharge my 1984 bronco 351 Cleveland on straight Autogas (liquid petroleum gas) ... I've read a number of posts and articles on s/c'ing EFI, but nothing seems to talk about s/c'ing older carbie systems or non carbie/EFI systems.

the specs on the engine I own and want to supercharge are as follows:
351 Cleveland 4V with flat-top pistons, 2500 stall converter, edlebrock street torker, 2 1/2 inch single exhaust from extractors. its been reconditioned and built up to 350hp by fordmuscleparts, an auto shop down the road... and now I want to go to straight gas and a supercharger (I'm currently on a duel fuel setup ... 750 vs holley/single 350 cfm LPG carb)

so firstly, can it be done?
secondly, how and with what type of supercharger?

I want power down low in the RPM band, and obviously nothing that puts too much strain on the engine as a whole.

so I want to hear ideas and thoughts!

thanks
- Sean

 

7psi boost on a screw-type supercharger. my suggestion would be a whipple charger. you have enough engine for that. you'd be able to run it on pump gas assuming you don't have over 9:1 compression.
here's a link: http://www.whipplesuperchargers.com/...sp?ProdID=1162

 

when I say gas I dont mean petrol
... I'm talking about what Americans call propane and Australians call gas or 'lpg'
I'm trying to supercharge a straight Propane 351c.

 

ohhh

no clue about propane. sorry.

 

I sent off an email to whipple regarding propane supercharging for my 351 clevo... and I recieved this in reply.
a bit discouraging. :/

__________________________________
I'm sorry, but we do not offer a supercharger system that will work with your Ford motor at this time.

Thank you for your interest,
Shonda
---------------------------------------

so, how come Gasresearch australia supercharges straight propane engines.. with whipple blowers? as can be seen in the following picture:

http://www.seanstrucks.netfirms.com/lpgsupercharge.html

I was looking forward to some information from whipple. seems they dont know whats going on.

 

Supercharging will work just fine. All you are doing is increasing volumetric efficiency (the amount of air traveling through the engine). With LPG you have the advantage of higher octane, (less chance of detonation) but the disadvantage of fuel delivery. In your case you do not have any electronic fuel delivery so what you will have to do if find an LPG carburetor that can flow sufficient air. My guess is that you will need something in the department of 900 CFM if you are going to run 6 psi or so. Your next greatest challenge is the plumbing, unless you find a carb that is a direct bolt on to the kit. Once you have it together you would tune it for fuel delivery and timing just like you would a normally aspirated engine.

Let us know how it turn out.

 

right then. its always heartening to talk to a no-b*ll***** mechanic.
I've rung around 4 Propane fitters, and I came across a bloke who is very straight up. he tells me no problem on installing an Eaton M90 positive displacement pump on a straight propane system. so I'm researching the following;
All prices in Australian dollars (AUD)

generation 4 M90 Supercharger $ 2,897.00

Dual Propane carbs total of 920 CFM (no price on them so far :/ )

pulleys & belts. approx $400.

I already have all the other Propane equipment, (tank, lockoff valves) as I was running dual fuel beforehand.

now I just need to get the rest of the money together, and start buying the bits.
I'm wondering if I will need a better exhuast setup. I currently have 4-2-1 setup from each bank through to 2 1/2" single pipe.
when I start the buying I will include digital pics of the progress.

- Sean

 

Scopie, Hi

Have you thought of going 100% LPG. If you do that you can ditch the carbs and use an LPG mixer fitted directly to the inlet of the charger. All that is required is to balance the vaporizer which usually requires a vacuum line from the inlet side of the charger to the rear of the vaporizer diaphragm and a flow adjuster in the line to do the balancing.

I run a Rover 3.8 with an Eaton M112 and 100% LPG using this method and it all works very nicely.

 

One fun note about propane is that it's equivalent octane rating is MUCH higher than "petrol", and when it's decompressed it's also MUCH colder than normal gas. The ideal setup would be to get a big honkin supercharger, switch to straight LPG, and inject the Propane AFTER the supercharger. This would act as it's own intercooler, since most roots blowers heat up the air significantly. Between the higher octane and natural intercooling, you could run some serious boost without knocking.

What's your compression?

 

Agelder, your right in what you say. I've been looking at how to inject the LPG after the charger and still get a good mixture. The problem is that 1cc of liquid LPG vaporises into about 250cc of gaseous LPG so getting the mixture right could be a major headache.

If it was well sorted I reckon that boost levels around 25psi could be easily acheived with compression ratios around 15:1+

You would have to ensure that you used pure Propane as the octane rating of LPG can vary from company to company. LPG usually comes in at 98-102 octane with pure propane up around 108. The other nice thing about running Propane is that it needs more ignition advance than petrol which means you dont need to back the timing off at high boost. The flame front travels around 15% slower so you need to get the spark in sooner. Propane also benefits from a bigger spark which is why I run a Hyfire, Promaster, and Unilite.

My current setup runs a modest 7psi at a compression ratio of 12.5:1 although I'm fabricating a new pulley to run 10psi.

All the best, Roskco

 

One way of injecting after the supercharger would be to machine a spacer of about 1" of good quality phenolic or aluminum and insert your propane injector(s) in there. Getting the mix right would be rather tough, and definitely require the investment in a wide-band O2 sensor. Would be a really kick butt project though!