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Dual overhead cam Hemi.

A pair of 426 dual-overhead cam Hemis might have been produced in 1964 to counter Ford's response to the 1964 426 Hemi, the 427 SOHC, but when NASCAR ruled against Ford's engine, there was no need for the overhead-cam Hemi.

Neither of the DOHC Hemis were ever placed in a car; one was destroyed, the other moved to the Kansas City area. (source: Muscle Car Review. Thanks, Stéphanie Dumas.) Recently, famed engine builder Larry Shepard told us that he has the A-925 cylinder head and other related parts, purchased from the late Dan Napp.

An article by Tom Shaw in Mopar Muscle went into more detail. The DOHC Hemi was project A-925, and it would need to be much more powerful than Ford's SOHC 427, but still rugged enough for racing - and able to conform to NASCAR's rules. Two possibilities were considered, according to Shaw - one using two cams positioned between the heads, in the "valley;" four valves on each cylinder were operated by lifters, pushrods, and lifters. This expensive setup was an unused contingency plan. Nearly as ambitious was an engine with aluminum heads, dual overhead cams, and, again, four valves per cylinder, with pent-roof chambers. (Chrysler had been working with four valve per cylinder engines for a never-completed Indy run in 1963.)

The dual-plane intake manifold had eight runners per side (Chrysler was into efficient and innovative intakes) and made of magnesium - but designed for a single four-barrel carburetor, as required by NASCAR.

The cams were driven by a cog belt, using external cog wheels at the front of the heads. Because the cams were directly above the valves, valvetrain mass was low, so the engine could rev high - a 7,000 rpm redline was specified, high for the era.

Shaw wrote that no DOHC Hemi ran under its own power; they were driven by an electric motor to check the valvegear. Research stopped in 1964 when NASCAR banned the SOHC 427 and Chrysler's own race Hemi. One Chrysler DOHC Hemi reportedly still exists.

Jon Field wrote that there was a third (at least) Mopar DOHC Hemi made — and that he owns it, a 301 cid aluminum-block-and-head engine with twin cams, two cam covers on each head (the plugs are between them), hydraulic tappets, brass valve seats, and four Weber two-barrel carbs (165 cfm each). He says the oil pan holds 10.6 quarts, and that the engine has stainless steel headers, and an aluminum intake; it is apparently functional and runs on regular gas. We don't have any information on where it came from and whether it's a Chrysler effort or an aftermarket modification.

Meanwhile, Chrysler alumnus and historian (of The Ramchargers) David Rockwell told Mopar Action that the A925 engine was a fake — a completely nonfunctional piece meant to impress Bill France into banning Ford’s SOHC engine (Stewart Pomeroy agreed). The one engine was run by an electric motor. The story goes that Chrysler racing chief Ronnie Householder learned about the ban from Bill France, and the engine was then destroyed.

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