Rover V8 holley size?

[simon]

I've got a rover 3.9 bored to 4.0. Its a fairly tuned motor but will a holley 390 be suitable or should I go for the bigger 600cfm?
Thanks

[STEVE G]

Simon
Split the difference and go for an Edelbrock 500.Much better carb for general road use and a F**k sight easier to set-up.
Steve G {-}
GE427-Rover 281ci.

[russell_ram]

A Holley 390 is perfectly adequate for your motor. Formula is

(cubic inches/2)*(max rpm/172*VE= required carb cfm.

60 cubes per liter, Volumetric efficiency around 80-85%.

Do the sum and you'll end up showing a requirement for a 350- ish cfm carb. (VE=0.85, max rpm 6000).

Fitting a large carb will just reduce the air flow rates through the carb ruining fuel atomisation and making it difficult to tune and, in the extreme, reducing the vac to a point where the secondaries might not open correctly. Double pumpers will be even worse. If you want a carb that leaves 'headroom' for more revs, capacity or tuning later, then go for a 465 Holley or 500 Webber as Steve says.

Russ