2276 Jetting / Venturi suggestions

[richierich]

Hi all. Motor is a 2276 with Web 86C, 44x37.5 heads and 48IDA carbs with no 3rd progression hole. CR is 10.2:1. Weekend street car with weekend drag racing every four weeks or so. I have just changed emulsion tubes to F2's from F7's in an effort to get rid of a stumble on transition from idles to mains.

My jetting with the F2 emulsions now is:

42 Vents
Mains: 160
Airs: 200
Idles: 65
Idle airs: 120

With the F2 tubes and the jetting above, the stumble on transition has smoothed nearly completely. Any other suggestions on the jetting for now?

I have a trip to the dyno booked which is a couple of hours drive but wanted to ask you guys if you think I might be better swapping the 42mm venturis to 40mm or even 37mm?

Thanks

[Dan Ruddock]

Get the third hole. F11 e tube help also.

[richierich]

Err, thanks for that. Anyone any idea whether there'll be any benefit going down slightly on vents?

[neil68]

It really depends on whether you want to focus on ET or streetability. My 2332 cc with the previous 44 mm intake valves, Web86C, IDAs, 10.7:1, raced best with F2, 42 vents, 65/120 idles and 180/220 mains, this was racing at 2,200-3,500 ft elevation. 40 mm vents might also work fine with F2.

If street driving is more important, then go with F11 and 37-40 vents.
_________________
Neil.

Der Kleiner Rennwagens
68 Beetle 2332 cc, 204 WHP
12.5 seconds @ 107 mph
Dynojet Test: https://www.youtube.com/watch?v=M9B_H3eklAo

[jason]

Get some Berg vents and have both.

[maui]

i say you are good [maybe 170 main]. main thing you get good ignition and plugs and a good exhaust. Oh yea a tranny that can handle. Aloha

[deadkombi]

Had the same problem with a similar engine combo and with the 2 progression holes I eventually changed the venturi to a 39 and it ran awesome. Had 60 idles and 160 main, 120 idle jet holder and 200 air. You can make it rich to get through the progression, but it will fowl plugs and lose HP. I tried a few sets of emulsion tubes as well F7,F2 and ended up with F11. It even ran much quicker at the track and gained almost 1/2 second ET with smaller vents. 13.2 in a standard 57 bug with 4.375 gears on 205/15 street tyres. Good luck cheers.

[richierich]

Thanks for the comments so far fellas. Just to provoke debate on this subject, the below in bold is regarding F11 tubes on VW motors taken from another site - hence the reason I went with F2's as I read they were more suited to larger motors. For those of you suggesting I run F11's, why is that? The F2's are certainly proving better than the F7's thats for sure but if F11's might be better again then I need to investigate.

'This tube has been used as OEM tube in smaller cc engines running venturies of 28-36mm. Larger O.D. of tube reduces fuel reserve in jet well and may create dangerous lean condition in large cc engine. Best used in 1600-1900cc and 28-36mm venturi, or engines with extremely strong vacuum pulses in intake. Main jet of 145 or under. May require air corrector over 200 to prevent over-rich condition at higher rpm. Better used in 40 or 44 IDF'

[74 Thing]

Doug Berg grooved venturis as referenced above

https://www.thesamba.com/vw/forum/viewtopic.php?p=7750868#7750868