"street" engine is going to be negligiable. Dyno tests I've seen between
different carbs (and different CFM's) in Mags like Pop hot rodding tend
to show only small differences between ANY carbs as long as they aren't
grossly mismatched to the engine.. They recently compared 650 750 950
and 1000 CFM holley HP's on a hot 400-ish cube Small block Ford and
found only about 8 horses and 15 foot pounds between them... with of
course the 750 CFM being the slight winner over the 650 and 950 with
best throttle response and torque at low to mid range and basically
worthless hp gains from the bigger carbs that then couldn't even pull
the dyno brake down at 2000-2500 RPM's etc. The lesson being that too
small a carb (650) will take away a couple HP and boost low torque and
give great throttle response, the "right" carb will get that HP back and
keep most of the great throttle response and low torque. Too big a carb
will leave you with bogs, terrible response, limp wristed low torque,
and only show a power improvment at the top of the RPM band.
MM (Mustang Monthly) did a dyno test of 480 CFM Autolite and a 600CFM
holley at one point (they also tested a 600CFM Autolite against the 480
at one point) and found for a stockish (only a header and cam and dual
exhaust) 302/289 that the smaller carb not only made more torque and
idled better, it even made more top end horse power. This was AFTER
tuning them both for best power on a dyno with a wideband o2. The
Autolites comparo showed the same tendency but reduced the gap if I
remember correctly. The 480 4bbl is a fuel atomizing machine. Annular
boosters, simple design, no body gaskets below the fuel line... My money
goes to rebuilding a shoebox, it's even made out of better metal (cast
aluminum verses pot metal.
The Edelbrock is just a Carter AFB, as such is it a good performing carb
that is highly self metering and so its easy to keep in tune and almost
never requires tinkering with. I have one on my 401 Nailhead and never
touched it, just plunked it down and it runs like a top. Starts up in
normal weather like it's fuel injected.
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