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FRPP Z304 Small-Block Heads - Draggin' Ball
Ford Racing Performance Parts Lets Loose With An All-New Small-Block Head For Serious Street/Strip Performance
Horse Sense: With the Z head, Ford Racing Performance Parts has come full circle. Back in the early 5.0 days, its first cylinder head was a streetable-but not emissions-legal-offering called the J302. The company moved through a series of e-legal GT-40 variants, and now it's back to a streetable, but non-e-legal rumbler in the form of the Z304.
There's a new head in town, cowboy. It's from Ford Racing Performance Parts (or Ford Motorsport SVO, if you prefer to live in the past), and it's already selling in land-rush numbers because, as FRPP engineer Hank Dertian put it, "They work really well and they're cheap."
Always a potent combination, that. But work how well? Around 500 hp on a 347 with suitable camming and breathing, according to FRPP. How cheap? Less than $450 per head, mail-order.
Now there's one trick to that price. In a departure for FRPP, the new Z304 is sold bare, not complete. This is because FRPP found the more hard-core GT-40 head buyers were changing valves or springs. So FRPP figured on going for a lower price and letting these more serious head-swapping customers finish the head as they see fit. Considering the rather high performance of this head, it seems the typical Z304 customer might even have some valves or such left over from previous projects anyway. And, the GT-40 heads continue for the straight bolt-on crowd, so everyone should be happy.
Finishing Z304 heads requires a valve job, valves, springs, retainers, and keepers, and the supplied guideplates need to be bolted down under stud-mounted rockers of your choice. On our pair of Z304s, the machine shop said the guides needed honing as well due to some minor bellmouthing.
Using prices from Dougan's Engine & Machine, where our work was done, the three-angle valve job ran $200, honing the guides $48, and assembling the heads $50. Good valves-such as our Manleys-are $15 apiece, valvesprings are $140, 10-degree retainers are $48, locks are $26, and the cups $36. You could save $60 by moving down to 7-degree locks and retainers. Rocker studs from ARP are about $44. Add all that up and it's $1,688 for a pair of heads ready to rumble. You may be able to do better, of course. We should also say Dougan's found the castings exceptionally clean-an FRPP trademark-and there was no need to mill them as they were dead flat.
And for your money you get plenty of cylinder head. All the numbers point to a performance potential right up there with any of the current hot-topic, inline-valve, streetable heads-anything short of a Yates head, in other words-and definitely running away from something like a GT-40 Turbo Swirl. We'll explore more of this in an upcoming issue, when we can run these heads on our new 347 dyno mule.
FRPP also has a reputation for delivering what it promises, especially when it comes to proper casting thicknesses, durability, general finish cleanliness, and that tough-to-define but important attention to detail. As Hank Dertian said, "We ran enough durability on them that we're comfortable with them." The deck thickness is "huge," so durability under forced induction is assured and generous milling for compression increases are allowed.
Just the same, the castings are fairly light at 27-28 pounds, and Hank says cooling is excellent. "The single-piece water jacket core is like a work of art. It does a really good job of cooling the valve seat and sparkplug.
"They're great out of the box [up to 285 cfm on the intake] and will respond even more. They're street-able, but not an embarrassment just for the strip." Think of them as darn sporty castings that can still live on the street-sounds perfect to us.
FRPP cast up a bunch of these heads to start, and because they've been selling so well, the company just ordered another batch of 500. Supply is no problem, so if you want a set, they're likely at your favorite dealer.
Finally, don't be surprised if these heads begin showing up elsewhere in FRPP's catalog. Ed Lyons, the FRPP engineer in charge of crate engines, was giving the Z304 the ol' dyno workout on some of his crate engines at press time, and the first returns were promising. And you thought there wasn't room for another small-block Ford cylinder head.
Machine HeadOur pair of Z304s went to Dougan's Engine and Machine for finishing. There, co-owner Ray Field said the heads looked outstanding and required no more machining than honing the guides and cutting the valve seats. Those with a sanding roll and some time could scuff off the rather minor lip of material at the valve seat/casting interface. Other than that, the only other improvement would be the usual custom porting job.
While cutting the seats for a three-angle valve job in these bare heads is listed by FRPP in all its sales material, honing the guides is not. Ray noted a bit of guide taper in a new head is fairly common, and the taper he encountered was not excessive. Still, for a performance head, it may be something you'll want or need to address, or your pair may not have any taper.
One item that did give them pause, however, was the suggested parts list FRPP encloses with the heads. There FRPP lists Crane springs and associated parts and Manley valves, but in Dougan's estimation, the valve and spring package comes out too short using a standard height valve as specified. So-equipped, the valvespring installed height was only 1.600 inches, 0.200 inch shy of standard and 0.300 inch shy of what the FRPP-specified spring specs call for.
All this points to a taller valve, which is no big deal if the head is properly mocked up and checked before the valves are ordered. Depending on the spring, retainer, and valve combination used, the spring installed height could actually end up a bit tall, leading to shims under the rockers and a slightly longer pushrod to keep the rocker arm geometry correct. Again, it's all part of setting up an engine, but it's something to be aware of.