Push hard and live
Join Date: Apr 2007
Location: Carson City, NV
I run an original weber manifold ( ie de-siamised ) with triple Dellorto 40's.
I had no power above 5,000 rpm when using 32 mm venturis - moving up to 36 mm gave great power at the top end . I have now moved back to 35 to give a little more power lower down . Any size 34 or below gives a high rpm power loss
air corrector 210
I wonder if there is a cam timing and/or lift issue with your engine? My 2300 is using 35mm venturies, and with the revised RJ cams, I have a very strong and flat torque curve all the way to 6,500. I've also got the same or more low RPM torque as I did with the original cams using 33 mm chokes.
The 2300 has a 575cc per cylinder displacement, whereas the 2600 has 433 cc per cylinder (very close to a 1750 4-cyl). That's 25% less displacement per cylinder. A 25% smaller choke (by area) would be somewhere between 30-31 mm.
It sounds to me like your upper RPM power loss is being caused by a restriction other than the venturies.
Carson City, NV
59 102 Touring (first Alfa $500 running)
65 Sprint GT (2nd Alfa, $500 daily driver)
102 Sprint (never did anything with it, but wish I had)
74 Berlina (first new car - now certainly rusted into oblivion)
61 Giulietta Spider G-Prod Race Car (where is it now?)
84 Spider Veloce (rarely drove it, so sold it)
86 Quadrifoglio (Dull car - no more 115s for me)
1971 Montreal "The Full Monty". Fair winds and following seas
59 102 Touring Roadster - restoration complete, enough Alfa for any rational man. Or irrational, for that matter
Two 1946 Stampe SV4C (c/n 294 "Rocinante" - wife's favorite airplane. RIP), and c/n 235 "La Bon Temps Femme" (gone to a new home, but never forgotten)
Zlin 50LA (+9 -6 gees, titanium spar, 1200 lbs, 260HP rumored to now be in Brazil)
1946 Luscombe 8A
Starduster Too (recently spotted at the Nevada City, CA airport - over 20 years and an entire continent separating it from our stewardship in Binghamton, NY)
1955 Cessna 170B (wife taught me to fly tailwheel in this)
64 Mooney M20E ("Rambo". My faithful steed for over 30 years) Nearly 50 years old, and just returned from a trip to Argentina in him
Newest in the fleet
1967 Piper Super Cub on Wipline amphibious floats (a true "all terrain vehicle")
2010 Triumph Thunderbird
You can snap roll an Alfa only one time...