By the year 1967, the domestic horsepower race was shifting into overdrive. Ford and Carroll Shelby were enjoying the afterglow of winning Le Mans with the big-block GT40 in 1966. This was also the year that Ford redesigned the Mustang into a larger and heavier body style. But the 390 GT was disappointing from a performance standpoint so Shelby quickly decided to stuff the new 428 Police Interceptor (P.I.) engine into the GT500 Shelby Mustang.
The induction system is what sets the 1967 Shelby 428 apart from its more casual 428 contemporaries. These are original 600 cfm Ford / Holley vacuum secondary carburetors. It may not be immediately noticeable that Ford elected to mount the carburetors backwards and actuate them using a rather complex progressive linkage system fitted with a hefty throttle return spring .Photo: Jeff Lilly Restorations
But because Shelby was an innovator and a hot rodder, a single four-barrel version would have been pedestrian and hardly in keeping with his company image. So he opted instead to bolt on a bit more visual and performance appeal by topping the 428 P.I. engine with a Ford 427 Medium Riser 2×4-barrel intake manifold and a pair of 650 cfm Holley carburetors. While 1,300 cfm was clearly a bit of airflow overkill, it was not an unusual approach to performance in those days. Exhaust emissions and fuel mileage be damned – it was full speed ahead.
Each carburetor features its original metal tag. Since these are vacuum secondary carburetors, each carb uses a separate vacuum line routed to the intake manifold. Any kind of primary or secondary jetting change would require removing one of the carburetors to complete the task. The horizontal white tube is woven asbestos insulation for the choke heat source line originating in the passenger side exhaust manifold. Photo: Jeff Lilly Restorations
The engine in these amazing images from Jeff Lilly Restorations is nothing less than an homage to the time when Ford was topping everyone with its Total Performance approach to selling cars. Shelby merely dumped gasoline on the fire with his 428 and was reaping the rewards. This particular engine was under-rated at a mere 355 horsepower at 5,400 rpm.
To ensure the correct carburetors, the first place to look is on the choke housing for the factory part number C3AF-9310. This indicates these carbs were originally used on 1963 (C3) 427 engines, which was indeed the case for the Shelby 428 engine. The 2804 and 2805 List specify this application. The date code of 715 indicates the first carb was built in 1967, in January in the 5th week.Photo: Jeff Lilly Restorations
As with nearly all Ford engines of that era, this version is festooned with interesting little factory small parts that for the restoration artist are where all the Easter eggs can be found. We’ll start with some basic specs and then work our way through this engine top to bottom much like a tour guide through the hallways of a Ford 428 Shelby Cobra Jet engine museum.
The casting number C7ZX-9425-A reveals the intake as a Medium Riser 427 twin four-barrel version with a 1967 casting date which is the correct intake for this Shelby 428 P.I.Photo: Jeff Lilly Restorations
The 428 was Ford’s production answer to the demand for a 7 liter big-block that would be less expensive to build than the FE 427 that preceded it. The 428 was the largest within the FE family bloodline that started in the late ‘50s with the diminutive 332ci truck engine. The 428 continued to use the FE’s Y-block configuration but sported a 0.100-inch smaller bore but enhanced with a much longer stroke than its 427 cousin. The 428 Police Interceptor engine featured 10.5:1 compression and a mild hydraulic flat tappet camshaft. The block was also configured to support hydraulic lifters with oil directed to the lifters first and sported a nodular iron crankshaft and two-bolt main caps.
These reproduction Autolite suppression radio resistance wires are also marked with individual cylinder numbers and feature the classic orange Autolite spark plug boots. .Photo: Jeff Lilly Restorations
Many consider the 428 as merely a bored and stroked 390. The camshaft was essentially a 390 GT Mustang hydraulic flat tappet grind combined with a set of Medium Riser cylinder heads that are also similar to the 390 GT castings from that year. But it sounds more exotic if you state that these are Shelby GT 500 castings.
All Shelby 428 engines came with power steering and the required pump assembly which has been carefully restored.Photo: Jeff Lilly Restorations
Shelby used this engine mainly because it was the newest addition to the Ford line while the more race-oriented 427 was being phased out. But what the 428 P.I. may have lacked in bold construction, it made up for with an impressive induction sporting the 427 Medium Riser dual four-barrel aluminum intake and twin 600 cfm carburetors. Adding to the engine’s panache was a giant oval air cleaner and finned aluminium valve covers that connect you with Le Mans through bold cast letters.