Carb CFM?
 

Never been good with math. Who can figure out what CFM this motor should be running at? Has a 850 Holly DP on it now. Not a big fan.

• Block - 340220 .... 427T ...... 68-85 ... 4-bolt 1968-76 427 tall - cut .060 over, decked and lined bored
• Eagle 4340 forged / 4.250 Crank / 445442526385 - mains .000 / rods .010
• Zollner Forged Chevy .060 - 14cc Dome Pistons - Speed Pro/TRW L2399NF - Compression Ratio=9:1 / Dome Type=Closed / Pin Type= floating
• Rods - 621-3404 custom made by Kiekhaefer (6.405)
• Heads 3964291 RECT PORT - Valve size 2.19 intake, 1.88 exhaust, closed, 108.9cc (Crane Cams ported and polished)
• Bronze Valve Guides
• Valve Seals / 505-16 Comp Cams - ptfe, Positive Stop, .530 in.
• Harlin Sharp Roller Rockers / Heavy Duty Series
• 7/16 Pushrods and guides
• APR screw in rocker studs
• Comp Cams CCA-205 Camshaft Thrust Button
• Cloyes Street True Double Roller Timing Sets 9-1110 (4+ degree advance)
• Cran Solid Roller Lifters
• Crane Cams - Part #:138091 Mechanical roller tappet / Grind Number:TR-252/400-2-10, Basic Operating RPM Range:3,500-7,000 / Duration at 050 inch Lift:252 int./262 exh. Advertised Duration: 290 int/300 exh, Lift .680/.708
• Crane Valve Springs / 96886-16 / Dual Spring / coil bind 1.150 / Spring Rate 652lbs
• Oil Pump – Melling 10778C - Oil Pump, High-Volume, 25 Percent Over Stock, Anti-Cavitation
• Winters Industries Aluminum Intake Manifold # 396364 / 7-11 - 69 (July 1969) Marine, Ported and Polished by Crane Cams
• Holley 850 D/P model # 4150, 850 CFM - 80 jets and 6.5 power valve in both ends
• ACCEL 140001, Ignition Coil, Super Coil, 45,000V

imo,the 850 is a good cfm for a 496 with 9.1 comp ratio that will see a max of 6500 rpm.if you had a good cylinder head and a good single plane intake a 950 would be my choice.

If your going to spin any kind of rpm I would use an 1000hp.

What type of exhaust? If that cam is on a 110 lobe ctr there may be a problem.

mark,,i hope your running the correct piston with that closed chamber cylinder head..from my expierance a dome piston and a closed chamber head is closer to 11:1..

I think Bob told me that it has 114 L/S so I’m not worried about the cam and exhaust.
The motor has been together for a few months now and is quite strong. Just picked up another motor so I can clone the K motor and it just got me thinking. You see people over carb all the time and I have no clue how to figure it out so I posted here. Looks like the guys back in 1969 with nothing but a slide rule knew what they were doing.

Summit racing has a carb calculator on their site. I've used it before and it's usually pretty much dead on.

http://www.summitracing.com/expertad...cfm-calculator

Using the calculator above, your engine size and a max rpm of 6500, an 850 carb is almost perfect and a 900 is the top of the line.

It has an open plenum dual plane with reworked closed chamber rectangular heads and just 9:1 compression...along with all the other stuff.

An 850 will be perfectly fine and a HP1000 will not just aloow a little more air in, but also, and probably more importantly, has more 'tunability' with most all it's fuel tune variables being able to be replaced with screwdrivers.

As many times I've seen guys over carb an engine, I've seen an equal amount of under carbed engines.