How would a pair of DCOE 40's cope with big revs? Let's say for example, an 8000rpm 1300 with a 300+ cam? Would they not be ideally suited to such an application?
Well, the bloke I know who races National hot rods used to run a MASS racing All steel 1700 Ford Crossflow up to 9800rpm on carbs, they were 50's tho... I'm not sure what size carbs the little Berg cup screamers run?
40 and 45 DCOE's are advertised on the tuning websites in Germany. I wasn't sure if there was a different kind of carb (like with Holley's for the big V8's) that are designed for smaller engines that can be better tuned for consistant high revving engines. So Weber DCOE's certainly can cope with the revs then. Hopefully the right jets and tubes can be found for them if I go this route, most probably from Germany, Sorg etc. I've got some brand new GSXR 600 (42mm-39mm) throttle bodies that I'm thinking of using on the 1300 and, of course, switching to a fuel injection setup so it can all be fine tuned. But this might create more headaches by not knowing any fuel or ignition figures to form a base map for the 1300. (Plus the added expense of buying the MS ECU, wideband lambda kit, various other sensors and ignition components... and a lot of time tweaking it all!) So I dont know whether to go the carb route, to speed things up (a lot!), or to spend a lot of time getting the most from an unknown setup which may produce a better outcome. Bike carbs (cheap) vs Weber DCOE's (not as cheap). Would bike carbs be worth a look? Would they be a little better than the DCOE's? There are a handful of examples using bike carbs on 1300 lumps. All in the name of possibly competing in hillclimbs and sprints next year as I think circuit racing will be too expensive in the long run and as RobT has mentioned in previous threads with hillclimbs/sprints, you've only got yourself to blame if you have an accident, unlike circuit racing, where pretty much anything can happen. It's an idea for the time being.
No probs. You can use up to a 36mm choke in a 40, which will supply a 1300 turning 8000rpm with plenty of air & fuel. Though if you get a 1300 (any 1300 using a choke per cylinder) to a power level requiring a 36mm choke you'll be on the cross-over between 40's & 45's, oh and producing AROUND 140hp !
Cheers Mr Hillclimber. I would certainly be happy with just over 100bhp/litre from the little 8v. The 16v setup would be too advanced to start out with I feel and I have no room for another engine, which removes the option of running a complete 1.4 16v in secrecy mode as well. Yamaha '03 R6's use 37mm carbs, as you say, plenty of air there. Would there be any advantages of using bike carbs over DCOE's? (apart from the costs) Could the setup of the bike carbs be left alone, if they were to find there way on this fairly mad 1300?
As long as the engine is getting all the air and fuel that it needs (which it will with a 36mm choke in a 40 or 45 DCOE) then i dont see any REAL WORLD advantage in using a bike carb (other than cost). In fact, i've only ever seen one hp comparison with Webers vs bike carbs (Mikunis i think) and the Webers were MUCH better than the bike carbs (on a strong hp Ford Pinto engine... it may not be so critical on a smaller engine). I'm not sure what the availability of needles (or whatever else a bike carb uses for calibration) are but DCOE's have a HUGE range of adjustability via various chokes/jets etc and would be my choice on that bases alone. You maybe lucky and find you air & fuel requirements are similar on yr 1300 car engine compaired to a 600 bike (bigger capacity/less rpm vs small capacity/high rpm) but LUCK and SIMILAR wont win you hillclimbs !
Southern carburettors.... 020 8540 2723 (London area) or Northhampton Motorsport.... 01604 766624. Both should hold good stocks for jets/chokes/linkage etc and obviously new carbs but at a price ! Try and find yrself a pair of s/h carbs, 40's should be easy enough but buy from a recommended source, lots of people will tell you "they were working fine on the car mate".... but why did they ACTUALLY take them off ! Good 45's are a little harder to come by because they are more sought after but can be found. Take a look through Motorsport news (out every wednesday) in the classifieds at the rear.
