cam/carb combination

pauldyworth · #1 (**permalink**) 10-21-2003, 11:45 AM

Only just found this site - wow what a great source of information!
Anyway hi everyone, I have a 72 European Spider which requires the engine to be rebuilt. I therefore am looking at this as an opportunity to possibily uprate it. Presently it runs on Dellorto 40's and the standard European cams. My query is if I keep the 40's, should I run an 11mm cam, or could I get away with a 12mm one, or should I be looking to change to 45's if I run a 12mm cam?

**GTV4EVR** · #2 (**permalink**) 10-21-2003, 04:03 PM

No personal experiance, but I am trying to make the same decision for next year's rebuild. Kevin at EB Spares in England tells me that you need the 45s to take advantage of the 12mm cams he sells (Colombo).

**GTV4EVR** · #3 (**permalink**) 10-21-2003, 04:05 PM

Is this easier to see?

genericwood · #4 (**permalink**) 10-21-2003, 05:24 PM

No personal experience with running Dellortos and 12mm cams. But I can tell you Wes Ingram (Spica Guru) says a modified pump with 40mm throttle bodies can benefit from the 12mm cams. I would be surprised if you couldn't get some benefit from the extra lift with the Dellortos. But I'm sure you would get even more with the 45's.

Erik

**papajam** · #5 (**permalink**) 10-21-2003, 05:49 PM

Welcome to the Board, pauldyworth!

Keep in mind that it's not the barrel size (40 vs. 45) that lets the engine breathe; it's the choke (venturi) size. There's a good writeup on choke/barrel selection here and although it's based on the Weber DCOE, I'd think the pricipals would be the same for Dellorto. It basically boils down to at what RPM is peak power produced.