Forum Member CHDCAT provided this documentation and wonderful pictures of these unubtainable heads, truly a part of the 351C history and lore.
thank you Chad for sharing this with us.. ~blizz
Iron SKE-2290 SBF Canted Valve Heads – Purchased from Smokey Yunick
Basic Part Number: SKE-2290 (Under Intake Port)
ASK Number: ASK 6923
Assembly: SK 42573 ASSY
Additional Markings: RH & LH
Additional Markings: F/L
1. The heads are dry-deck, as was common for Indy heads and some others
2. They have larger combustion chambers than a common Ford production 351-4V quench head
3. The spark plugs holes are moved over but are fully compatible with conventional 351C flat top pistons
4. They have removable valve guides but K-liners are recommended when preparing the heads for modern use
5. They use conventional B302/351C valves
6. They use conventional B302/351C guide-plates with minor mods but valvetrain geometry varies according components used
7. Water outlets at the end of each head
A former Pro Stock Ford Pinto racer bought the first set of these heads in 1970 from the legendary Smokey Yunick. When Bunkie Knudson joined Ford after a stint with GM, he recruited Smokey. Smokey did some R&D for Fords Indy and Trans-AM programs in the late 1960s.
After Smokey utilized the first pair of these heads for dyno testing, they simply remained on the shelf in his shop and were never returned to Ford. The “ASSY” inscription is proof that they were part of an engine assembly which normally means an assembled engine package for some form of testing, such as the dyno.
The first pair of these heads Smokey sold to the ex-Pro Stock racer had 427 Ford Tunnel-Port tulip valves and were immediately subjected to a full competition port job, port-plated and campaigned in both NHRA and IHRA over the course of several seasons.
The second set, which are pictured above, were purchased in 1978 as a backup pair to the original set, but were never modified (ported and port-plated) for Pro Stock competition since the first pair never broke beyond repair. Various Ford engineers were not happy to hear that Smokey parted with two pairs of these heads, even though it was nearly a decade after their original creation and testing.
The SK42573 is the left head and SK42572 is the right head. They were both modified on print Ford engineering #42574 by plugging the 351C water passages. The above two prints (SK #s) call out the dimensions for the water holes in the ends only. These changes were requested by Ford engineer Ken Buchanan on Sept 3, 1968.
A later SK print by Ken Buchanan details modifications to a “Shelby 289 manifold modified to fit” these heads. That was likely a T/A style dual four intake, welded and machined to work with 351C (then known as 351GT) heads.
There are special intake gaskets also listed for these heads. Curiously the SK book calls out head ASK 7103 to be used for the basis of the modifications, not the one stamped into these heads. The one of the pair of heads furnished is serial #9 of that modification.
The scratched X was for casting personnel to observe as an indicator the heads weren’t to be machined under normal casting plant protocols, but were to be done at the Engine and Foundry Experimental Engine Division.
The chamber shape is not what became reality and these heads were replaced by another chamber shape modification very close to the final B302/351C version. These heads also do not have the stellite seats that the final race version heads used.
While there are SK-numbered valves specific for these heads. It was always strongly advised to use modern one-piece stainless or titanium units, depending on the application.
That’s my story, and I am sticking to it
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