Gas research and Impco or OHG converter

[Anonymous]

The turbo buidup is almost complete. Engine is assembled, twin plate clutch almost sorted.

I've got some questions about my LPG setup. I have a lot of parts that I've collected over the years. The car in atmo form runs a crappy amos ring and complex converter which will not be used. I'm going blow through because i've chopped a Ford truck intercooler (1metre wide core! fits with some chopping of teh grill). I have an old gas research mixer, OHG X2 and OHG X1 converter and a large looking IMPCO converter which has not yet arrived from an ebay purchase along with 2 IMPCO 300A carbs. My manifold is a redline 2 barrel. I've never used any of these bits together. I have been told by a OHG seller that the OHG and IMPCO converters are not quite sensitive enough to suit the gas research carb. Any body used OHG/IMPCO converters on a gasresearch carb before?

My ideal would be to run the X1 with the X2 (the X2 is a much smaller converter which I hope will be more sensitive at part throttle leaving the X1 to handle the high boost stuff) withe the gas research carb.

I have Jay Storers book on LPG setups, it has a lot of pictures of 300A carbs, but they don't really look suitable for setting up as blow through. I know i need to set up a balance line for the converters regardless of which carbs I run. If the gas research isn't going to work i suppose i could run 2x 300A Impco carbs.

Any advice would be appreciated.

Dom

 

[xctasy]

I'd like to have a go with just one of the CA425 as one will give deliver up to the amount of the E-seires converter. That's 325 to perhaps 400 hp.

I'd copy Colin Townsend's landmark 265VG Valiant Turbo kit with an Ultraflow intake, 500 Holley 2-bbl, CA425, and E-series, and I'd look at the TC-1 boost restrictor and an Evo or RX-7 intercooler. This set-up worked because Impco's love big engines.

The twin CA 300 conversion could work if you get the right four-barrel Holley throttle body baseplate. You just have to make certain the car is able to use almost 700 cfm of carburation before you even add the boost. Most dual Impcos are for engines in the 350+ range.

For a 250 cube engine just to run two, it will need a hi-stall converter, and you have to limit the boost to about 10 psi. There are good silicone diaphragms which will last a long time, but blow-throughs on CA 300's are not the best idea at all.

The twin CA 425 is better, again for 350 cube V8's, as it has a better non-diaphragm air/gas valve that will take more boost. With twin L-series converters, it would work well.

Or triple CA125 carbs. One 325 hp E-series converter will be okay for short bursts to 400+ hp before it freezes up.

The balance line is just a means of making the converter respond to vaccum properly. The ECI port isn't used for lean cruising. The set-ups are simple, but it is not as responsive to small throttle openings. It's designed for bigger engines.

The Impco service manual from 1984 was simply the best option. The Impco service site will help answer problems, but it's American based, and those guys don't like to push the envelope as its a factory based link. Turbo six cylinder installations are not there cup of tea.

 

[Anonymous]

main thing with high fuel demand, is to use a big(or better two converters.)i ues 3 impco 225 mixers ,and two E converters on my normally asperated 265 hemi(6200rpm and 360hp) and my son-in-law uses 2x225 and 2xL conveters on his blow through supercharged 208 holden 6-goes like stink!

 

[xctasy]

The 225 is a brilliant carb. I forgot that it is very common in Australia, because it ia not very common at all in NZ. I've never seen one in my life, but have seen many 125, 300 and 425's.

If you can get them, two or three CA225's would be the ultimate.

 

[Anonymous]

225's are very common in oz(picked up another on the other day for $30-just because!)if you want me to get ,and send you a few,let me know.i can also get the rebuild kits for them too.if you can,dump the 300a's,the're mainly a duel fuel mixer and realy don't give much power on a straight gas system

 

[xctasy]

Thanks. That Ak Miller used only CA 425 and CA 225's on his factory Ford Experimentals underscores what you say.

The main problem with the CA 300 is know one knows there are two types. The 216 hp A1 is a little anemic on a really wild cammed six. The A5 is a 270 hp carb, only 17 hp down on the CA 425. Main issue is the awfull, and I mean truly crapfully woefull POS intakes used for dual or sole fuel instillations. That's why I build my own. Mine works. Impco, ABER, SAF ones don't. The 300 carbs are very cheap in New Zealand. Most guys don't even know what they are.

You pay 400 ping for a CA 425 or 300 for a CA 225. You need to start exporting them to New Zealand....

 

[George]

Hi,

I used a Gas Reaserch carb with century convertor on my sigma turbo (Blow through, intercooled). The car was a rocket with no flat spots and savage top end power. Economy was also very good.

One thing I recomend is the installation of a big blowoff valve to vent the excess boost when you back off. I found that with no/small blow off value the build up of pressure during backoff would cause the convertor to dump extra gas causing a nasty flat spot during gear changes. Another thing to experiment with is what location you take the balance line from for the convertors. Closer to the turbo, the richer the mixtures - this is even worse if you have an intercooler with a large pressure drop.
I also had to grind the metering rod in the carb to adjust the mixtures.

The best part of the build was sorting out all these little things..

Good luck