Convert from SU / CD Stromberg to Impco recommendations.

Propane, Butane, LPG, GPL, C3H8, C4H10
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storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Convert from SU / CD Stromberg to Impco recommendations.

Post by storm » Sun Jul 22, 2018 3:17 am

I've been asked lately if I would convert some classic cars to LPG while keeping the original manifolds if possible. I myself have a manifold and triple 1.5" CD Stromberg carb setup off a 186 CI XU-1 Torana (classic Australian muscle car). The 202 CI version had triple 1.75" CD Strombergs. So I am wondering if there is an easy way to choose what Impco to use in place of either an SU or a CD Stromberg.

Other classic vehicles, that I know of, that use these carbs are Morris and Austin Minis, MG (A,B, & C), any British car with the old A Series engine, some Volvos, Range Rovers.

I have been thinking a 55-500 would be a good swap for a multi carb system but I'm not sure what would be good for a single carb system (maybe a 225?), Any advice/shared experience welcome.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

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C3H8
Posts: 1001
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Convert from SU / CD Stromberg to Impco recommendations.

Post by C3H8 » Sat Aug 04, 2018 12:53 am

Hi Storm. I'm not familiar with the engines you mention, however I suspect they are not really hi revving hi HP engines based on the vehicles you describe. The 55 series is certainly the best consideration, however it is one of my least favourite IMPCO mixers. It tends to wear out quickly because of the strong intake pulses in the intake manifolds. For a single carb setup . The 225 seems reasonable but it depends on the HP and RPM limit.

storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Convert from SU / CD Stromberg to Impco recommendations.

Post by storm » Sat Aug 04, 2018 4:12 pm

Hi C3H8
None of these cars are typical of North American muscle cars but some variants have racing heritage and are performance vehicles despite their size. None of them are slouches, so to speak, in touring car guise, and this is why they are sought after but with the price of petrol (anywhere from $1.40 a litre to $1.60 a litre depending on where you live) compared to LPG (averaging about $0.86 a litre but as low as $0.75 a litre) and the owners desiring to still use the vehicles they see LPG as a viable alternative.

The 186 XU1 was a race car (touring not drag) in its day (early 1970s) it took on much more powerful 351 Clevelands in XY Falcons (Ford GTHO Phase 3) in 500 Mile endurance race and won. Great engine in a light car. https://www.uniquecarsandparts.com.au/h ... ifications. It replaced the 350 Monaro as GMH's premier performance vehicle.

British A Series engine at Bathurst 500 mile race http://www.motorsportretro.com/2013/10/ ... -bathurst/

Rover SD1's also raced at Bathurst and (albiet in EFI form) won the Group A category in 1984 using the 3.5 litre Rover V8.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

jono
Posts: 347
Joined: Wed May 16, 2007 11:46 pm
Location: New South Wales, Oz

Re: Convert from SU / CD Stromberg to Impco recommendations.

Post by jono » Mon Aug 13, 2018 5:27 am

Hello Storm and others,

I have seen a 1967 HR GMH ute on propane and it retained the triple Strombergs or SU's that were on it

I only got a quick look at it once, at night 20 years ago so memory is vague

I think it was set up on the old basis of just supplying vapour via a hose to all three carbs and let it take it what it wanted.

Weren't there ancient conversions where the vapour hose was just fed into the wet fuel carburettor and um, hoped for the best ? And that is how basic propane can be.

My only experience with Stroms/SU's is one of despise, sticky plungers needing sewing machine oil and holes in diaphragms and kits over priced for English cars - so I know zip but thought should add what I had seen and admired

The guru who did it was a bit of a genius and no longer in the industry, or the area for me to ask

jono
Posts: 347
Joined: Wed May 16, 2007 11:46 pm
Location: New South Wales, Oz

Re: Convert from SU / CD Stromberg to Impco recommendations.

Post by jono » Mon Aug 13, 2018 5:28 am

Hello Storm and others,

I have seen a 1967 HR GMH ute on propane and it retained the triple Strombergs or SU's that were on it

I only got a quick look at it once, at night 20 years ago so memory is vague

I think it was set up on the old basis of just supplying vapour via a hose to all three carbs and let it take it what it wanted.

Weren't there ancient conversions where the vapour hose was just fed into the wet fuel carburettor and um, hoped for the best ? And that is how basic propane can be.

My only experience with Stroms/SU's is one of despise, sticky plungers needing sewing machine oil and holes in diaphragms and kits over priced for English cars - so I know zip but thought should add what I had seen and admired

The guru who did it was a bit of a genius and no longer in the industry, or the area for me to ask

storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Convert from SU / CD Stromberg to Impco recommendations.

Post by storm » Sat Aug 25, 2018 4:28 am

Hi Jono
I like the SU CD type carb but I acknowledge they can be a pain if they are not looked after.

I have heard of, but not seen, people feeding LPG into a SU CD type carb in a similar fashion to what is done when small generators are converted from petrol to LPG. It is something I would consider doing but not with a genuine XU1 CD Stromberg, I'd get some new replacement units to test the idea out on.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

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