Coming late to this thread by will throw in my experience:
I converted a 383SBC in a manual transmission performance street application from 4 barrel 750cfm Holley double pumper clone (
Proform Parts 67200 - Proform Race Series Mechanical Secondary Carburetors - Overview - SummitRacing.com ) to 4 x 47mm OER (DCOE clones) on a crossram (
http://www.webcon.co.uk/Downloads/PCV401-MAR07.pdf ) to Holley commander 950Pro (
Holley 91005201 - Holley Commander 950 MPFI Systems - Overview - SummitRacing.com ) all inside 12 months on top of an identical engine configuration. A good back to back test, albeit subjective.
I am a fussy bugger when it comes to tuning so I put real effort into getting each combo optimised at both WOT and for driveability and economy using decent test gear. I tried 4 750 4 barrel carbs before adopting the proform carb - it was by far and away better than Holley 750 vac sec #3310, Holley DP #4719, Holley DP with annular boosters, in both response, economy, and outright power. All Holley carbs were atop the same edelbrock performer EPS intake. Engine has mild hyd roller cam, 10.6 c.r.
Key observations:
Proform 750: Good economy when idle restriction orifices tuned properly, would take a punch to full throttle from an idle roll in first gear and just light the tyres with no bog or fuss, tractible down to about 1300 in 3rd 4th and 5th, useful torque 2-5k, usable to 5500-ish.
OERs on crossram: a glorious looking and sounding excercise in pain. Spent weeks and weeks getting them as perfect as poss. In the end good driveability could only be delivered with poor economy, they could not take large thottle openings cleanly unless the main circuits were already flowing regardless of what I did to the pump shot, better that the holley below 2k if you rolled into the throttle in a tall gear, about the same in the mid range, dead after 5 grand.
Holley MPEFI: ECU is rubbish but hardware is good. Controlled with a Link g4 ECU (
G4 Xtreme — Link Engine Management Systems - plug-in & wire-in aftermarket ECU's ) running sequential injection this has nearly OEM quality cold start and idle manners, potters down to 1000rpm in 3rd 4th and 5th while climbing and pulls cleanly (much better than the carb'd set-ups) about the same as the 750 up to 5k, and a little more life than the 750 set-up up to my self imposed cut-out at 5600. Best economy of all but not by much over the 750. A lot of the benefits are associated with the ability to control ignition timing and to alter timing and fuel for changing ambient conditions. Much more induction noise than the 750 because there is no fuel or booster venturis sitting in the airstream. The difference at the top end will be mostly down to the intake manifold - 750 was dual plane, MPEFI open plenum. LOots and lots of time out on the road with Innovate LC1 and laptop getting it perfect. Be prepared to work to get the best out of it. Datalogging capability is a real boon to tuning once you get the hang of it.
Summary: I won't go back to carbs but in a maximum effort application living between peak torque rpm and peak power rpm a good 4 barrel on a good open plenum intake is still hard to beat and is cheap. EFI properly done is superior in my experience in the real world on the street, but is more expensive and does demand you put the effort in to get the benefits.
Cheers, Andrew
).
