Newbie Here. I just bought a Scout II with a Ford 460 and need some
carb. advice. The 460 is spec. out as follows:
BIG BLOCK 460 BORED OVER 30 (ABOUT 500 HP-600 FTLBS TORQUE)
WHOLE MOTOR IS BALANCED
CLAY SMITH CAM ( 2240 DURATION, .525 LIFT)
ROLER ROCKERS AND LIFTERS
DOVE HP HEADS
HOLLY 650 DOUBLE PUMPER
ALUMINUM WIELAND STEALTH INTAKE
MSD TIMING CONTROL
ALUMINUM RADIATOR 4 CORE
My buds tell me the 650cfm is too small to realize the full potential
of the 460.
What do you guys think?
Two major considerations are max useable engine RPM which
your cam grinder should be able to help with and the
displacement of the engine which you can calculate easily.
As far as your HP & torque numbers, thay are a bit
optimistic with a 650 carb - I don't know that that size
carb can produce those numbers. If you use "calculate
carburetor size" in Google, you will find numerous
calculators. If your engine can produce 100% volumetric
efficiency which few naturally aspirated engines can
achieve, it will need something over 800 cfm at 6000 rpm. I
don't know for sure but, I think your cam duration is 240
(typo?) with a .525" lift which should give you good mid
range if properly installed and timed. This is a relatively
mild grind for good torque. I would suspect that your
engine would not produce peak HP much above 5000 rpm if that
much with that duration and lift. If that is the case, the
650 will be about right. The worst thing you can do for
your engine is over carb it. It will only gag coming off
the bottom end. Forget what your "buds" are telling you and
go with the what the numbers tell you. Unless your Scout
is strengthened considerably with much improved brakes and
chassis, I would not want to unleash the full potential of
your 460 very often - it will break things.
Thanks for the good advice.
My Scout hasn't arrvied yet. I bought it on eBay. The specs. I quoted
came from the eBay ad, which I shared with some friends who mentioned
the carb is too small. I'll do the goggle search as you suggested.
Here is the standard formula for figuring out carburetor size.
CFM = (cubic inches x rpm) divided by 3456
VE = (cfm x 1728) divided by (cubic in. x rpm)
Another CFM but takes into consideration Volumetric efficiency
CFM = (cubic inch x rpm x volumetric efficiency) divided by 3456
This should give your friends something to do for a couple of minutes.
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