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Rescue Diver
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- 1979 CJ-7 with a fiberglass body and 1982 wide track axles, 258 I-6 with a 1995 4.0 head, HEI distributor, Motorcraft 2100 Carb, T-18 wide ratio tranny, Super Lift Springs and 33s, a 1997 BMW 328i, and a 2010 REDLINE CONQUEST TEAM Cyclocross Bike. :)
Regarding carb CFMs for a AMC 258 i6 / 4.2l , I found the following on Forums.Off-Road.com and this point is very well made.
"the maximum flow is dependent on the displacement of the engine, and max rpm the engine will be subject to. So calculations aside, the max flow (CFM) the AMC 258 i6 / 4.2l cid engine can handle at 3300rpm, 100% efficiency is approx 226cfm."
Since no engine is 100% efficient, the real CFM requirement is much lower. A carb in the neighborhood of 300 CFM is all you need for an engine that is built to redline at around 4000 RPMs.
Ford didn't put 287 and 300 CFM carbs on their V8 302 engines in mustangs and trucks just for the fun of it, and they weren't too worried about gas mileage back in the 1960's. Even sticking a bigger 4 barrel carb on one of their stock V8's that came with a 300 CFM 2 barrel wouldn't give you much more HP without making a lot of other modifications like cam, heads and exhaust while your at it.
"the maximum flow is dependent on the displacement of the engine, and max rpm the engine will be subject to. So calculations aside, the max flow (CFM) the AMC 258 i6 / 4.2l cid engine can handle at 3300rpm, 100% efficiency is approx 226cfm."
Since no engine is 100% efficient, the real CFM requirement is much lower. A carb in the neighborhood of 300 CFM is all you need for an engine that is built to redline at around 4000 RPMs.
Ford didn't put 287 and 300 CFM carbs on their V8 302 engines in mustangs and trucks just for the fun of it, and they weren't too worried about gas mileage back in the 1960's. Even sticking a bigger 4 barrel carb on one of their stock V8's that came with a 300 CFM 2 barrel wouldn't give you much more HP without making a lot of other modifications like cam, heads and exhaust while your at it.