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475hp 347 Stroker Ford Small Block - Catching Zzzzs
Building Simple Speed With A 475hp 347 Stroker.
This buildup started with a desire to run a test on one of Ford Racing Performance Parts' crate engines. Actually, we wanted a motor capable of running with the LT1- and LS1-powered Z28s of the world, and thought the 450hp 347 listed in the FRPP catalog looked like the perfect choice. Checking out the specs on the M-6007-C347 crate engine listed in the catalog and online, we see that the 5.0L crate motor was actually a 347 stroker in disguise. That's one of the great things about running a stroker-the ability to disguise it as a lesser combination. The 347 stroker looks identical to a standard 302, so who knows the difference?
How many street races have been won by strokers passed off as 302s? The M-6007-C347 crate motor had plenty to offer, including a Sportsman block, a stroker crank, and even a Canton oil pan. Unfortunately, we weren't able to secure one of the crate motors, so we decided to do the next best thing-build one ourselves. Actually, the buildup was more to illustrate the power offered by a healthy stroker motor than to specifically duplicate the FRPP crate offering. But since we had the major ingredients (heads, cam, and stroker internals), this is what might be expected from the crate assembly as well.
Starting from the top and working our way down, we gathered all the necessary components to assemble a solid street stroker, the highlight of which was a set of the FRPP Z304 aluminum cylinder heads. Loyal readers will remember that we tested these heads in our Ultimate Guide to Cylinder Heads, and the FRPP offerings proved themselves quite powerful. When first introduced, the Z304 heads were offered bare, requiring that enthusiasts assemble the necessary valvetrain components. Since that time, FRPP has seen fit to offer the heads as completed assemblies under PN Z304DA. The assembled heads came with stainless steel valves measuring 2.02 on the intake and 1.60 on the exhaust. Also included in the mix was a set of beehive valvesprings that offered 130 pounds of seat pressure at 1.800 inches installed height, and 293 pounds of open pressure at 1.200 inch. This valvespring combination was perfect for a healthy hydraulic roller cam profile of up to 0.600-inch lift. In fact, the valvesprings did not experience coil bind until 1.085 inches, giving more than 0.100 inch clearance with a 0.600-inch lift cam. Naturally, you will want to measure retainer-to-seal and piston-to-valve clearance as well.
According to the FRPP catalog, a set of CNC-ported Z304 heads (PN M-6049-Z304P) are also offered, but these were not available to meet our dyno schedule. The supplied literature said the new CNC heads flowed more than 300 cfm, and we look forward to running them. The as-cast Z304 heads were no slouches, though, with intake flow over 275 cfm and exhaust flow near 220 cfm. Credit for the impressive flow goes to the choice of valve sizes (significantly larger than those employed in stock 5.0L heads), the generous port volumes of 204 cc (intake), and 85 cc (raised exhaust), and overall efficient port shape. Though our heads did not feature CNC porting of the intake and exhaust, they did include machined combustion chambers. The Z304 heads required use of dedicated roller-rocker arms, something we consider mandatory on any performance buildup anyway. FRPP supplied a set of its M-6564-F351 roller rockers. The Z304DA heads did come with laser-cut guideplates for use with 5/16-inch pushrods and the necessary 7/16-inch rocker studs. With all the impressive hardware, it's easy to forget that the aluminum con-struction kept the bare weight of each head to just 27 pounds, making for significant weight savings over factory cast-iron counterparts.