I took the coupe to one of our local Autocrosses yesterday and the Flatsides did work pretty well (well enough that I'll be selling of the complete GX carb set-up soon) The only real issue is the course being to super tight meant there was a section where the motor was below 4K in 1st gear and I can't quite use full throttle. I'll be heading back to the dyno to sort the last bit, I changed needles before the event, motor is great but quite not perfect. I ended up 25th out of 80 cars and with some tuning I think it's possible to get in the top ten, 15-27th were only 4 tenths apart and I was 7 tenths behind 11th place so not having to drive around the set up would easily make that up. All of this of course would be a total non issue on a race track as the car never goes below 4500 RPM on the two tracks I run.

The fun part was the motor now revs like mad and of course folks in Vettes, WRX,s and EVO's finished behind me. All said and done I would recommend the Flat Slide Carbs................not for street use of course. Well when I get the car back on the Dyno I'll let you know what goes, the claim on FCR Flat Slides was they add 10% and have immediate throttle response which they do even with my probably only having them 85% dialed in......they are huge improvement and for left hand drive cars no need to move the brake master.......very happy as the car scoots.

Tom

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Good to hear that TOM will be interested in the settings once setup properly
as many run the GX grind on this forum.

Pics or ban!!

Ok Pictures added....not great but I'll get some more, ignore the tatty engine bay (please)

Also made some adjustments to the needles (moved clip up) and it appears it will now pull from 3000 RPM's...........back to the dyno one more time.

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Hey Tom,

Looks Grand.

So why wouldn't you recommend them for street? Do you have an issue with the engine spluttering when you go from closed throttle (I mean flat idle) to absolute WOT?

Thanks for reporting how it all went.


I can see myself trying these as soon as I have the cash.

Could you explain to me the fuel line setup? Do you have a return? and if so is that how the carbs like to be fed?

As the carbs are tuned now if you were cruising along at 2500 RPM's and slapped the throttle to the floor , the motor will bog and nearly die, this is what I'm working on now. I'm pretty sure they can be tuned to be streetable but given their flow rate you would probably gain very little on an otherwise stock A12, so you'd need to have a less street more race tuned engine. Also there is no choke.........starting is fine as you just pump the pedal and the accelerator pump will fatten up the mixture plenty..............but you'd have to wait a couple of minutes before you drove off...........not the best if you're dashing off to work. The other aspect of this is gearbox, a standard 4 speed drops 3000 RPM's between 2nd and 3rd so you could potentially be revving the car way more than needed in street driving just to keep the RPM's up. As it stands right now my car will putt along and the transition will likely be fixed so there is no bog but even after that it's still going to be happiest with more revs. I have loads of experience with tuned 2 stroke street bikes and they are cool for about 6 months, after that and they tend to be a grind day to day.

Now if we're talking a Friday drive my classic to work then I'd have no problem running them on the street.

Fuel set up is a slam dunk, I'm using a pressure regulator set to 1.5 PSI. At 3 psi it was leaking as the needles were unable to hold back the flow. No return lines or anything like that.

Tom

i wonder if you need angle like that to get your carbs working better chis? thats a massive angle.

Nah Mik, mine are sideys and these are downdrafts.

The problem with mine is that they were crappy on the inside, needed a major clean.

Hey Tom,
Fcr's are known for it's mass amount of flow hence the bogging. But do you think if you had smaller fcr's like 35 or 32's it could be run as more of a street car? talking about a12's here. As for a15's it could handle fcr39-41's?

sweet! but what angle the carb is? is the carb actually downdraft, or is it sidedraft?