I had one of the first CHP 427 kits, in fact you can say I did some early R&D for them, they hadn't got all the bugs out at the time. But as a fairly experienced engine builder, I was able to give them some decent input (especially with regard to the possible need for the smaller base circle cam) that they incorporated int otheir later kits.
A small base circle cam means the lobes are cut off of a smaller base diameter core, this allows for the clearence required for the long 4.17" stroke crank's connecting rod shoulders to have adequate running clearance around the cam lobes. The first kits used shoulder bolt connecting rods that would actually extend into the cam tunnel; they can be close but IMO you need at least .060" clearence at the closest points with the cam degreed in. I ran a gear drive for added insurance. It's fine but I told them the early kits would have been disasterous if built by a novice builder who might not have thought to check. I suggested they go to H beam rods with cap screws which is what they used in later kits.
My 427 (really 'only' 426, just like the "real" 427fe actually was) is a real screamer, IMO don't buy all the bunk about short rods, side loading, it's very overblown. If a motor goes slow and won't rev high with short rods it's usually because you don't have enough head, induction or cam for the motor! Don't take my word for it, ask Jon Kaase, the 30+ IHRA mountain motor pro stock engine builder (815" w/1.35:1 rod ratio) as well as the PHR Enginemasters Challenge winner who won with a 470" short rod FE. True short rods motors don't make good sustained high RPM endurance type motors but for street cars (that run at part throttle 85-90% of the time) and occasional week-end acceleration (drag and road race) motors they are tough to beat with the right heads and cam.
As far as builders, you may be money ahead to buy a very reasonably priced short block from an experienced veteran Ford builder like Keith Craft. If you build it yourself, I reccommend using only the best, most reputable Experienced Ford machinist in your area, get your block, square decked, line honed and bored with deck plates and the bellhousing (and preferably a blowproof scattershield in a Cobra...remember your right calf is alongside with the clutch!!) torqued in place.
I'd run a head with intake flows of at least 250 @.400 lift and ~280 @.500 lift, at 10:1 and a ~236-240 @.050 cam with ~.540 lift. Along with a Ported Victor Jr and an 800cfm carb and min 1 7/8" primaries you can make right at or slightly over 500hp/500lb-ft and have an extremely broad powerband with perfect street manners, Jeckyl and Hyde, a torquey *****cat for cruising and a tire shredding monster when you put your foot into it. Guys put bigger cams in these cars but really wind up making lower average torque and power, the simple reason is that with typical Cobra style sidepipes the primary tubes wind up around ~36" long, that's really too long to allow a bigger cam motor to really raise the peak torque RPM high enough to really wring out the extra big end HP a bigger cam would provide, so instead the big cam costs more upper bottom and mid range torque (especially part and roll on throttle) than is gained in top end power. Unless you want to run a shorter 28-30" primary and a 3 1/2' by ~10-12" collector before the muffler, there's really no good effective way to make the cobra sidepipe system produce the kind of hp a bigger cam motor might make on a dyno with drag race style headers, might as well make the most out of the torque curve you have.
Just my .02 cents.
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