250 crossflow with a 750 cfm no way? I wonder?

[Anonymous]

Yes it probably is but how this? Someone on this forum some time ago mentioned that (I think it was comp cams) that recommended at 750 cfm carb with one of it very serious performance cams. he commented that this was overkill.
Started me thinking I remmember a guy I worked with not that long ago who (didnt no alot about cars) but claimed he had an unbelievably powerful XE falcon with a 250 crossflow in it. I quizzed him over it many times the only thing he knew for certain was that it had a 750 cfm four barrel carb on it and was dynoed (he didnt no outright power) but said they told him with the power and weight figures it should excellerate from 0-100 kph (0-63 mph approx) in 4.9 seconds.
He sold the car (astronomical fuel bills) and the old guy who bought had to tame it down. I wonder???

 

[xctasy]

Think on this. A NASCAR can do 650 hp on one 650 cfm double pumper with a restrictor plate. A 750cfm carb of any decription is really over kill. but engineering can triumph over common sense any day. My mate had a 750 cfm 4MV Rochester on his Cain 4-bbl manifolded 202 12-port Holden ute, an it ran passably..with a lovely staggering slurp when the secondaries kicked in.

290 hp with a Hi-po Active intak manifolod, 650 doble pumper and alloy head 250 has been verified by Aussie magazines.

Danny, old next door neighbour, had a 277 cubic inch Chyrsler Hemi six. It ran a 650 4-bbl double pumper on a stock 2-bbl intake with a dubious adaptor. And it worked really well. Fuel bills were huge, but in a 2900 pound Aussie Charger R/T it was a traffic light Gran Prix winner.

If you can make the primary circuit work, which on a #3310 Holley 750 vac sec is equal to one 500 cfm Holley 2-bbl carb anyway, you can do any thing if the engine is cammed, compressed and intaked, exhasted and geared as a screamer. Fuel economy will be worse than a 351 on a bad drinking binge.

Some people have real trouble even getting a 350 or 500 cfm Holley 2-bbl to run well on a six. Heaps of dyno time will be needed, and when the secondaries cut in, it had better like a nice cool drink of premium gas, cause it sure will get some.


If I had funds, a 750 cfm Holley would need a solid lifter or roller cam with about 325 deg intake duration cam with 345 on the exhast, and about 312/318 deg at 50 thou lift. Total lift would need to be 580 to 600 thou, and opreating range would be 3200 to 7400 rpm, from my info. Idle would be non-existant. Compression would need to be 12:1, it would have to run VP Red C16 fuel or perhaps a 50/50 water methonol mix in a water injection kit to quel detonation. Exhast would need to be over 2.5 inches, and you'd need a Active manifold and cross flow head. If the head, cam, rods, pistons, oil pump and sump windage could take it, you could get at least 375 hp at 6700 rpm and over 340 lb-ft. (up to 1.39 ft-lb per cube is available from a well sorted OHV engine)

Or check with what the Argentine 221 engines run from our team of South American Screemers. They have wild, wild cam combos for there 221 2V Max Eccono (ME), and Special Performance (SP) engines. The 250 2V is similar, and would cope with there cams better.

Any one else (like some one with an Engine Analyser Program) want to verify or comment?

 

[MandarinaRacing]

EXECUTE

you can do any thing if the engine is cammed, compressed and intaked, exhasted and geared as a screamer. Fuel economy will be worse than a 351 on a bad drinking binge.

Definately...... MY KIND OF SIX!!!!!!!!!

 

[Mustangaroo]

Well we pick up our 4V intake this Sunday, plan on installing it on my son's Mustang 200 which has a Aussie 2v head, plan on swaping out the 2V intake and run a 4V intake with a Holley 650 CFM double pumper, this carb has real small primaries, about 1" 1/4" in size. Should keep the torgue up untill those huge butterflies (2" 1/2" open He is running a small 256 Insky cam...... When we get it running we'll dyno for results 8)

 

[Anlushac11]

Well we pick up our 4V intake this Sunday, plan on installing it on my son's Mustang 200 which has a Aussie 2v head, plan on swaping out the 2V intake and run a 4V intake with a Holley 650 CFM double pumper, this carb has real small primaries, about 1" 1/4" in size. Should keep the torgue up untill those huge butterflies (2" 1/2" open He is running a small 256 Insky cam...... When we get it running we'll dyno for results 8)

I think the housing and bottom butterflies are the same with my 450 and your 650. The main diference is the venturi's and the boosters.

I think a 650 will work but you may need to reduce the size of the shot from the accelerator pump.