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Discussion Starter #1
Hey there everyone,

I'm about to convert my XC van with a 378 stroker clevo to straight LPG.

This motor on petrol is producing somewhere around the 350- 400HP mark.

The two systems I'm looking at are:

1. Single Impco 425 mixer which replaces the carby altogether

2. Sprintgas mixer which fits on top of my Holley (650vac sec) and uses it as a throttle body.

Is anyone familiar with these rigs. I'm particularly intested in the Sprintgas rig because it appears to be a better flowing system and it's also cheaper. Gas Attack in Melbourne had one fitted to there 500HP big block Falcon hardtop so I figure it flows REAL GOOD!! :wnc:

Any advice would be appreciated.

Thanks,

Chris.
 

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I am usually very wary of things that sit over the top of a carby for mixing. Sounds too much like a 'standard' LPG install. Do you have any pics or links to a website so we can see what it's all about?
 

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Whats traction?
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The impco is a good carby, i run one on my 351 with a 700 series holley base and although its running lean its not the carby thats causing the problems.

Gas research is the only way to go for big HP though. Their twin throttle body setup is the best a very long way. As soon as i have the money it'll be straight on my engine!

If you decide on the impco PM me as i know a couple of tricks with them and if you live in melbourne i know some places that can help getting one setup right.
 

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Discussion Starter #5
I have had a look at the Gas Research gear. A friend of mine had the twin throttle body rig on her 351 and she was very unhappy with it. Lack of power and bad economy. I don't know what brand of gas she was using or what kind of mods the engine had (if any) and this was also about 5 years ago.

As for pics of the Sprintgas rig,

http://www.sprintgas.com.au/pgthree.html

The mixer I'm talking about is the Vortex.

I'd like to link to Gas Attack but they seem to have dissappeared. hmmm, that's not a good sign but I guess it's all too common these days.

The Impco 425 is only a 450cfm mixer. I would have thought getting 350HP out of one Impco 425 would be pretty well impossible. Twin 425's maybe.

The Sprintgas Vortex has proven it can flow 500HP and is designed for engines up to 8 litres. So even if it is a "standard" gas setup, a "standard" gas setup for an 8 litre engine makes for a "holy [email protected]#t!! get outta my way" gas setup on a 6.1 litre engine :) in terms of flow potential.

I'd be interested to find out what a twin throttle body rig from Gas Research would cost.

Thanks for the offer of the gas setup joints xdc351 but I live in Canberra. One question though, you say you ran an Impco 425 on a Holley 700 series base. I thought the Impco replaced the Holley altogether. What do you mean by Holley "base"? The throttle butterflies? Sorry if that's a dumb question.

Regards,
Chris.
 

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I don't see how it could flow enough to feed and angry 351 but I don't know enough about LPG to really be sure. If the guarantee it will flow enough for the job..go for it !
 

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Discussion Starter #7
I seem to recall something about them using two convertors to feed the one Vortex mixer on the 500HP big block. I can't find the magazine it was in now so I'm not sure. It was about 2 years ago in a Ford Performance magazine. A yellow XA or XB coupe. Of course the flow potential of this mixer is also dependent on the carby it's sitting on top of.

I'll get a quote from Gas Research anyway.

The Sprintgas Vortex rig is going to cost me $2,000 for the complete install including the tank, convertor, mixer and all the required fittings as well as setup.

For the Impco rig they want $2,500.

So if Gas Research is in that kind of ballpark then I guess I should consider it.

What would be really nice is one of the Sprintgas Electronic Gas Injection rigs. But that's more like $4,000 and a bugger to convert a Clevo cause they never had EFI standard so inlet manifolds have to be customised to do it. Windsor fuel rails fit though.

Regards,

Chris.
 

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Discussion Starter #8 (Edited)
The other problem is that the Gas Research dealer down here in Canberra is AGAS. I used to work next door to them and while I'm not prepared to tell you what I've seen them do because I don't want to get sued for slander, I will not ever use them or recommend them.

Which means that if I want a GR rig, I've got to get it in Sydney.

Regards,

Chris.
 

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A twin throttle body GRA setup on a stock engine would be such overkill i'm not surprised it ran like a dog. It's like putting a 750dp holley on one. But there is no doubt in my mind the GRA twin throttle body setups are the only way to make good power throughout the rev range on a tough engine.

The impco's can be worked to deliver way more than we have any right to expect from such a small carby. They are ment to flow 425cfm (hence the name), but actually flow a little less due to some factory restrictions. Gas seems run a lot more fuel per CFM than petrol carbies, there is no way i would expect my engine to survive to even 5000rpm with a 465 holley if i ran it on fuel.

But its more of a compromise with the impcos, inorder to get good high rpm flow, you overfuel down low, the GRA setup does not have that problem. 2 425's will not work unless your engine needs 900 or so petrol cfm's to make power, plus you'll need a tunnel ram.

The impcos require the butterflies (base) from a holley to regulate the air flow. It is a great idea as holleys are plentiful and hooking up accellerator cables to a holley is never a problem. The 425 just bolts onto the base and your away!

xa-coupe will get to see just how nasty one can be at the raid :evilsmoke

I don't know a single person running a sprintgas setup, anywhere, so I cannot make any suggestions on their performance.
 
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I make my own Gas mixer that completely blows the GRA stuff(and anything else) away!
In fact one of my mixers replaces two GRA carbs with ease.
email me if you're interested at [email protected]

Pete.
 

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Redneck Alcohol Racing
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my car used to be on gas, but once the new motor was built and i nailed it on petrol, i never considered ever filling up with the taxi's again, and hence i pulled off all my gas stuff
 

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351 XE on LPG
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I went with the Impco 425 because I wanted to keep my shaker. It's mounted on a 600 sqarebore throttle body. It is easy to tune and I've had no trouble starting it cold mornings. It's a greater mixer for a strong torquey street motor, but you'd have to run duals for revs and high HP. Height can be a problem then when running tunnel-rams.

One thing I don't like about the 425 is it needs a fair bit of vacuum above the carby to meter properly. I installed a K&N filter and it started running sluggish and wouldn't tune. It also started chewing up heaps of gas too. I put the old paper element on and immediately noticed the difference.

How does the Vortex work. Is it a mixer or is the metering done at the heat exchanger?

Does anybody know anything about the OHG X-450 carbs. The following web site (http://franzh.home.texas.net/engine.html) quotes . . .

"One other carburetor that has been excellent is the OHG X-450 (or also called the MM series). One or two X-450's with the model "E" Impco or the OHG X-1 vaporizer, and you have up to 900 bhp to play with (providing the rest of the engine is up to it). Use the same intake manifold options here too. Realize that these horsepower numbers are for a full race engine that is fully prepped. Just adding carbs on a stock engine will not realize its full potential."
 

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Discussion Starter #14
I have requested some more info from Sprintgas about the Vortex mixer but they have not replied yet. As soon as they do I'll post it up here.
Regards,
Chris.
 

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I have had a couple of 351 clevelands running straight gas useing the 425 impco gas carby.

i used the thermoquad base, (thats all a thermoquad is good for) and it works well, i have had the gas carby run well for years(aprox 10) with no probs on a very mild clevo, and in fact i still have the car now.

the only problem that i have is pinging up high, especially on hot days, i am running 302 heads, and i think i have too much comp, especially with the gas quality we have now compared to what we used to get years ago.

Im not sure how this set up would work with a high horsepower clevo??

i would have a look at the gas research set up, as i know of some people have tried that with sucsess too.

look at all the options available before you spend your hard earned dollars

jim
 

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Discussion Starter #16
It seems by all accounts so far in this thread that the Impco rig is good but may not flow well enough for an engine in this state of tune.

I am still trying to get info on the Sprintgas rig and Gas Research seems to be the standard for high HP LPG setups. It would be nice if there damn email address on there website worked though.

I'm also very interested to see what XR9UTE (Pete) has to say about his custom gas mixer. Pity he's in Perth though. It would be good to see one.

My engine currently revs to over 5500RPM under full load on Optimax without pinging so I don't think I'll have too many problems running LPG as long as I can find a decent supplier that doesn't sell crap gas.

There's a great brand name for a new alternative fuel for vehicles. We can run our cars on methane and call it CRAP GAS!! We'll make a fortune!!!!
:fly:
:cheeky:
:toilet:
 

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351 XE on LPG
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EXECJIM, recurving your distributor to suit gas should stop the pinging with your 302 heads. There are various posts within these forums that discuss the required specs.

How did you match a squarebore 425 to a spreadbore thermo base plate?

Rhett
 

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Rhett said:
EXECJIM, recurving your distributor to suit gas should stop the pinging with your 302 heads. There are various posts within these forums that discuss the required specs.

How did you match a squarebore 425 to a spreadbore thermo base plate?

Rhett
i just used the adaptor that came with the 425 gas carby, it was a long time ago, but i guess i stated that i had a spread bore carb.

jim
 

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I have a 351 with the impco 425 on the thermoquad base have had noprobs at all, it runs very smooth and still has enough power to run [email protected] in a ZH Fairlane. A friend has the twin gas research setup on a xb 351 and severly regreted spending the big bucks on it. It used a shitload of gas and no one could tune it properly.
 

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Discussion Starter #20
D'oh!!

Problem solved!! The guy I was buying this car from and had paid a deposit to has decided not to sell the car. So now I don't need to find out what LPG conversions are good anymore because I don't have a car to convert!!!

However, I am looking for one. So if you hear of any Ford V8 Panelvans around the Canberra - Sydney area, I'd appreciate a heads up.

Thanks,

Chris.
 
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