Hitting on all eight cylinders
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Hello all I have been nosing around on this forum since I decided my project would be Y block powered and I am amazed at the wealth of knowledge here and am looking forward to benefiting from it. As my first post I would like advice on some appropriate carb choices for 292 powered Model A. The specifications for the car and the engine are the following: Model A coupe on 32 frame ,Top loader 4 speed trans, 9" traction lock with 3.50 gear Bias ply 4.50'x 16 in front &.7.00's x 16 on the rear 31 inches tall estimated weight 2700 292 C1AE block .060 over Block heads and crank ,magnafluxed, hot tanked, and surfaced where needed. heads are ECL fitted with larger valves,new seats,and guides, Pistons, rings, bearings, cam, springs, and lifters from Mummerts pistons are stock type, cam specs are duration 270 @ .020, 234@ .050,lift .465, and separation of 108 valve springs are Mummerts recommended VS 105 The rods were reconditioned and new bushings installed New ARP bolts for the heads ,mains and rods The intake is a stock Ford ECZ-9425 B Distributor is a COAF 12127-A ( also has B9AF 12131B marking if that means anything) with a Pertronix module The rocker arm assemblies are rebuilt with new shafts and springs.and the rocker oiling holes were cleaned The rockers are ECG 6564 spark plugs choice is Motorcraft BSF42C gapped to 35 and finally will be using an inline PCV running from a Thunderbird valley pan with the rear road draft tube hole the long block was assembled by a friend with lots of engine building experience just not on Y blocks mostly FE's I intend to drive the heck out of this coupe with lots of highway miles and around town cruising. My goal is to have a reliable , good sounding , motor with some low end power ,reasonable gas mileage and no intention of racing on the street or the track As stated up front what do you guys recommend for a carb and does anything in this list of parts stand out as the wrong choice to be used with any of the other parts? Thanks in advance to all who respond.
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It’s not necessarily about the size of the carburetor but in how well it meters the fuel. The advantage a four barrel carb has over a two barrel carb is that additional increase in cfm that’s needed in the upper rpm ranges without sacrificing drivability in the lower rpm band. Many people forget that a four barrel carb does much of its running around in two barrel mode which is generally smaller cfm wise than many oem equipped two barrel carbs. That is why a properly tuned four barrel carb can get better fuel economy than a two barrel carb. As a general rule, when selecting a vacuum secondary carb, always select a size that would appear to be larger than needed. The nature of vacuum secondary operation has the secondary blades only opening the amount needed based on the air demand required by the engine which makes an oversized carb always being optimal in size and never under-carbureted. The older formulas for calculating carb sizing are geared towards stock engines with no modifications. Once head porting, better exhaust systems, improved intake manifolds, and larger camshafts are throwed into the fray, then those calculations tend to push for undersized carburetors. I’ve have extremely good results with the Summit 750 carbs on lightly modified Y’s with those carbs having good driving manners in the lower rpm bands and then good power outputs when the engines are stretched out a bit. The best of both worlds there. I have the Summit 500 vacuum secondary carb on a warmed over 272 in a ’55 Ford and while it’s a good driver, it is could use some more cfm when getting more aggressive into the throttle. Here are some links giving dyno testing results for Y’s using 750 cfm sized carbs. http://www.eatonbalancing.com/2015/05/01/unported-iron-heads-can-still-make-over-a-hp-to-the-cubic-inch/ http://www.eatonbalancing.com/2012/12/08/milling-heads-for-a-horsepower-gain/ http://www.eatonbalancing.com/2012/09/29/a-tale-of-two-330-inch-y-blocks/
 Lorena, Texas (South of Waco)
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