Group A Carb kit

[Chesney84]

Has anyone on here had any positive experiences with these - I know there are many butchered/ bored out venturi's out there that have been made by tuners, however I am talking about the kits you can buy from France with 26,27 or 28mm venture, replacement brass venturi and additional parts (and drilling to the carb). I saw a thread on here about a possible group buy a few years ago, but no feedback as to whether these were successful or not. Or am I just better off with a standard carb set-up properly? I have bought a second carb for the engine build, and last night ordered the rebuild kit from the club shop, but would like some feedback, either way I'm not fussed - if you guys reckon its not worth the Group A kit I won't bother and will save my pennies!

[Ian S]

The few people who'd tried one stated a bored one worked better. And eventually people stopped bothering with bored ones and just used standard.

If you're trying to make 250BHP through a tiny 25mm throttle, -area² of spindle shaft, then that seems like a restriction. I expect the choke just above is even more restrictive.

I guess another main problem is the carb doesn't really have the range to fuel accurately from idle to 250bhp, OE is only 120bhp. You have to chose your compromises to get it to deliver on maximum boost and excessively in other places.

Or just use something better.

I don't know if I knew what the Group A upper boost was, if they had one. Track racing cup series boost was set to 14PSI for all cars, so the I guess the carb was designed accordingly and perhaps is not suitable for 20 or 25psi?

[Chesney84]

I did read somewhere on this site about removing the choke entirely, smoothing out the step and using the lever to control the idle instead whilst cold - but I cant find where I read that now (any idea's?). They offer a 26, 27 and 28mm venturi, will need to have a think about what size I ought to go to though!

[Alex]

I'd just use a standard venturi to be honest...

[RussellT]

Alex is right. I had one of these and she ran like a dog. Prob OK on a race circuit but not for the road.
Save your money for something else like a limited slip diff.

[Ian S]

removing the choke entirely, smoothing out the step and using the lever to control the idle instead whilst cold

That how mine was. When starting in the cold it worked better that way than with the choke flap.

Might be some info here:
https://www.rtoc.org/boards/showthre...7078#post47078

And amongst these:
https://www.rtoc.org/boards/forumdis...ox-amp-Turbo-s

[Chesney84]

Thanks for the feedback, think I’ll stick with standard then and just give it a thorough strip, clean and rebuild, remove the choke flap and tidy it up inside then set it up with a wide band when I fit the engine. Cheers for the links Ian- knew I’d read it somewhere!

[Ian S]

I just thought that it might have been a factor that that carb was bored to 27mm or so and jetted for about 24psi boost.

It was probably a bit rich at idle and the choke flap made it worse.

On a fully standard carb maybe the choke flap helps. Your's will be re-jetted though.

we'd also cut half the throttle spindle away to increase the area there. But over about 10,000 miles, the remainder of the shaft became bent and started sticking, which was not tolerable. I posited that the each time the throttle plate was suddenly shut, the 25psi moving column of air, with the still spinning turbo then further spiking the boost, pushed hard enough to gradually do that damage.