Its still a realitivley free country, so use whatever. Enjoy whatcha do, and you cant make a bad call.
Except for downgrading to three 7448 Holleys with tiny 1.1875 venturis which will drag your peak power down, and remove mid range torque.
Peak rev range with 30.6 mm venturis on a 250 engine is 3600 rpm, and a open plenumb won't make a jot of difference.
CFM has nothing to do with improving any performance; duty cycle and venturi size govern this aspect.
The only way you can go down a carb venturi size without suffering a disapointing mid range and upper range flatness is by a higher compression ratio and a Restrictor Plate cam profile, the late Currie Industries 65 Mustang is an example; even though it had a low compression ratio, it ran on 87 octane.
There is a very specfic combo listed here that will get you close, but it'll be like a 86 with the wildest 303 cam, and you'd probably out perform it. Due to the cam and carburation, your rev range would require some gearing more like Franks 66 Shelby replica. Its a real car, with real performance, and some real science went into getting it to do 140 mph and sub 15 second 1/4 miles. None of that data is hidden. If you run it through a simulation program, you get the same power peaks with less rpm. It is a real 7000 rpm engne with 292 cubic inches. A 306 would drg the peak power rpm down a little with the cam specs.
Basically, peak power is its related not to peak carb air flow because (as NASCAR proved), even with Winston Cup steel restrictor plate, and a little 390 cfm 4-bbl, you can make 850 hp if you compress, cam, exhaust and use the right heads the right way to underscavege a 351 Windsor or pre EFI F452 block. In a similar way, the so called production Carrera Pamaerica has been dominated by 2-bbl stock gasoline engines that absolutely can make insane power very, very cheaply. Frank Curries car in the link above is proof what can be doen on below 9.25:1 compression and 87 octane gas.
The problem with the 2150 is that they were only 1.08 or 1.21 carbs, 287 or 351-356 cfm rated Fords way. With the advent of the 1965 Clean Air Act, Ford decided the last big two barrel was the 1964 to 1966 390 2100 series "C4MF-A"prefixed Autolite 2-bbl with a 1.33 venturi, and 424 cfm.
The SAE Net Hp in the 2-bbl 400 was about 172 to 180, then down to 159 to 163hp in the restricted exhaust truck era. Rated Gross was 260. I'm picking that with the 5.0 GT 1.21 carb, you'd get to 250 hp net fairly easily. The German DIN factory net hp was about 240 in the 64 to 66 2-bbl 390, or 280 hp Gross.
The work Currie Industries did on there Mustang
http://image.hotrod.com/f/9989744+w660+ ... _right.jpg
includes a cam specification, a intkae and exhaust target air flow, an intake manifold, and it would work fine with a 2150 carb fly cut or abrasive reamed to a 1.375" venturi. Normally, any Motorcraft carb has well over 160 thou of wall thickness in the casting. With 80 thou removed around the annular portion of the venturi, you'd get to a 1.375" venturi size fairly easily, enough for over 430 cfm. If it broke through, you can expoxy it back with JB weld, and resand with emery or wet and dry. Its been done before with 5200 Holley Webers, take them out another 160 thu easily for 336 cfm, up from 227 cfm.
a stock 5200 Holley Weber, which is 23 and 27, can be routed out to 29 and 31 mm venturis and still work, as well as flow 336 cfm at 3" Hg like this one by Mercury Marc (an Aussie told him how to do it!)
Without a very specfic cam duration, exhaust and intake flow development program, you stuck with these sizes for performance
For any thing port on port, irresepctive of grouped plenumbe, assuming a 5 inch from butterfly to valve head.
Up to 1.181" or 30mm,180 hp six
up to 1.260" or 32mm, 198 hp six
up to 1.378" or 35mm, 234 hp six
up to 1.496" or 38mm, 276 hp six
up to 1.575" or 40mm, 306 hp six
up to 1.653" or 42mm, 336 hp six
Up to 1.771" or 45mm, 390hp six
up to 1.889" or 48mm, 444 hp six
up to 1.968" or 50mm, 480 hp six
up to 2.047" or 52mm, 522 hp six
up to 2.126" or 54mm, 558 hp six.
As stated, ye canne change the laws of physics" unless you play around with the exhaust flow rates, compression, and find a signifcantly better way to deliver fuel to six cylinders. They've done that at NASCAR, ACTC, and LeMans where restrictor plates are common, but they have engineers with degrees to help them. As you can see above, I'm not against CFM figures, but CFM isn't the issue, its the size of the restriction in cubic inch of engine per square inches of venturi, a critical flow dimension which has defined drag factors under Bernoulis eqautions. CFM at a carb is pressure based, with a targed air speed of about 265 feet per second for Holley carbs, 4-bbl or 2-bbl. Its really got nothing to do with anything but having a fair, common base to rate things by.
Air doesn't care about CFM. Flow net analysis defines horsepower because engineers who are good at it (and Ford Motor Company has the best engineers around bar none), they rate engines on not just dynos, but in actual real world conditions.
I think the GT40 427 Dual Quad system was the best ever non Independent runner system around. It kicks a$$. But try fitting that kind to a six in line, and it won't work.
If you want to go to 30.6 mm venturis, factor in $400 for David Vizard at APT Fast to design a new camshaft and exhaust to suit your intake system.
Then get them to grind a cam blank to suit.
Don't try an cheat physics...its too expensive.
https://www.aptfast.com/ContactUs.aspx
92507 (Riverside Weather Forecast, CA)
Advanced Performance Technology
595 Iowa Avenue, Suite C
Riverside CA 92507
Phone: (951)686-0260
Toll Free: (800)278-3278
Fax: (951)686-2831
danton@aptfast.com
Except for downgrading to three 7448 Holleys with tiny 1.1875 venturis which will drag your peak power down, and remove mid range torque.
Peak rev range with 30.6 mm venturis on a 250 engine is 3600 rpm, and a open plenumb won't make a jot of difference.
CFM has nothing to do with improving any performance; duty cycle and venturi size govern this aspect.
The only way you can go down a carb venturi size without suffering a disapointing mid range and upper range flatness is by a higher compression ratio and a Restrictor Plate cam profile, the late Currie Industries 65 Mustang is an example; even though it had a low compression ratio, it ran on 87 octane.
With the right intake manifold, cam, and heads, you can get 350 hp from even a 289 with a box stock 4412 blueprinted 500 cfm Holley 1.375" venturi carb.
Even a 2-bbl (or especially a 2-bbl!) really likes single plane 4-bbl intake a lot better than anything Ford ever made for 1968 to 1985 2 or 4-bbls. If your very carefull, this might fit under the hood.
See http://www.hotrod.com/cars/featured/hrd ... g-fastback
http://image.hotrod.com/f/9267509+w660+ ... 8-hero.jpg
and this
http://image.hotrod.com/f/9267560+q80+r ... _large.jpg
Photo 8 of 15 | The Keith Dorton-modified 500-cfm Holley carb is the largest allowed in Currie’s Carrera Panamericana class, and it mates to an Edelbrock Victor Jr. single-plane intake with an adapter that’s hogged to match the carb’s bore size. Maximum power on the dyno was made with box-stock calibrations. http://www.hotrod.com/how-to/engine/ford-289-engine-buildup/#ixzz3ig86Xoy3 @HotRodMagazine on Twitter | HotRodMag on Facebook
The hot 289 two-barrel shown here made an impressive 352 hp at 6,700 rpm and 316 lb-ft at 5,000 rpm—on 87-octane gas—using a sensible combination of parts and preparation.
There is a very specfic combo listed here that will get you close, but it'll be like a 86 with the wildest 303 cam, and you'd probably out perform it. Due to the cam and carburation, your rev range would require some gearing more like Franks 66 Shelby replica. Its a real car, with real performance, and some real science went into getting it to do 140 mph and sub 15 second 1/4 miles. None of that data is hidden. If you run it through a simulation program, you get the same power peaks with less rpm. It is a real 7000 rpm engne with 292 cubic inches. A 306 would drg the peak power rpm down a little with the cam specs.
Basically, peak power is its related not to peak carb air flow because (as NASCAR proved), even with Winston Cup steel restrictor plate, and a little 390 cfm 4-bbl, you can make 850 hp if you compress, cam, exhaust and use the right heads the right way to underscavege a 351 Windsor or pre EFI F452 block. In a similar way, the so called production Carrera Pamaerica has been dominated by 2-bbl stock gasoline engines that absolutely can make insane power very, very cheaply. Frank Curries car in the link above is proof what can be doen on below 9.25:1 compression and 87 octane gas.
The problem with the 2150 is that they were only 1.08 or 1.21 carbs, 287 or 351-356 cfm rated Fords way. With the advent of the 1965 Clean Air Act, Ford decided the last big two barrel was the 1964 to 1966 390 2100 series "C4MF-A"prefixed Autolite 2-bbl with a 1.33 venturi, and 424 cfm.
The SAE Net Hp in the 2-bbl 400 was about 172 to 180, then down to 159 to 163hp in the restricted exhaust truck era. Rated Gross was 260. I'm picking that with the 5.0 GT 1.21 carb, you'd get to 250 hp net fairly easily. The German DIN factory net hp was about 240 in the 64 to 66 2-bbl 390, or 280 hp Gross.
The work Currie Industries did on there Mustang
http://image.hotrod.com/f/9989744+w660+ ... _right.jpg
includes a cam specification, a intkae and exhaust target air flow, an intake manifold, and it would work fine with a 2150 carb fly cut or abrasive reamed to a 1.375" venturi. Normally, any Motorcraft carb has well over 160 thou of wall thickness in the casting. With 80 thou removed around the annular portion of the venturi, you'd get to a 1.375" venturi size fairly easily, enough for over 430 cfm. If it broke through, you can expoxy it back with JB weld, and resand with emery or wet and dry. Its been done before with 5200 Holley Webers, take them out another 160 thu easily for 336 cfm, up from 227 cfm.
a stock 5200 Holley Weber, which is 23 and 27, can be routed out to 29 and 31 mm venturis and still work, as well as flow 336 cfm at 3" Hg like this one by Mercury Marc (an Aussie told him how to do it!)
Without a very specfic cam duration, exhaust and intake flow development program, you stuck with these sizes for performance
For any thing port on port, irresepctive of grouped plenumbe, assuming a 5 inch from butterfly to valve head.
Up to 1.181" or 30mm,180 hp six
up to 1.260" or 32mm, 198 hp six
up to 1.378" or 35mm, 234 hp six
up to 1.496" or 38mm, 276 hp six
up to 1.575" or 40mm, 306 hp six
up to 1.653" or 42mm, 336 hp six
Up to 1.771" or 45mm, 390hp six
up to 1.889" or 48mm, 444 hp six
up to 1.968" or 50mm, 480 hp six
up to 2.047" or 52mm, 522 hp six
up to 2.126" or 54mm, 558 hp six.
As stated, ye canne change the laws of physics" unless you play around with the exhaust flow rates, compression, and find a signifcantly better way to deliver fuel to six cylinders. They've done that at NASCAR, ACTC, and LeMans where restrictor plates are common, but they have engineers with degrees to help them. As you can see above, I'm not against CFM figures, but CFM isn't the issue, its the size of the restriction in cubic inch of engine per square inches of venturi, a critical flow dimension which has defined drag factors under Bernoulis eqautions. CFM at a carb is pressure based, with a targed air speed of about 265 feet per second for Holley carbs, 4-bbl or 2-bbl. Its really got nothing to do with anything but having a fair, common base to rate things by.
Air doesn't care about CFM. Flow net analysis defines horsepower because engineers who are good at it (and Ford Motor Company has the best engineers around bar none), they rate engines on not just dynos, but in actual real world conditions.
I think the GT40 427 Dual Quad system was the best ever non Independent runner system around. It kicks a$$. But try fitting that kind to a six in line, and it won't work.
If you want to go to 30.6 mm venturis, factor in $400 for David Vizard at APT Fast to design a new camshaft and exhaust to suit your intake system.
Then get them to grind a cam blank to suit.
Don't try an cheat physics...its too expensive.
https://www.aptfast.com/ContactUs.aspx
92507 (Riverside Weather Forecast, CA)
Advanced Performance Technology
595 Iowa Avenue, Suite C
Riverside CA 92507
Phone: (951)686-0260
Toll Free: (800)278-3278
Fax: (951)686-2831
danton@aptfast.com