What was the engine in a '67 Shelby G.T. 500 called, exactly?

[Brian Styles]

I'm guessing that your first instinct would be to answer that the engine was known as a "Police Interceptor."

And why wouldn't you? It's the term we've heard repeated for decades.... but doesn't make it correct, now does it?

The more documents we find and the more time we spend researching them, the more we have a new opinion....

Here are some of the documents we found (so much for consistency):

[ FORD DOCUMENTS ]

Ford Domestic Special Order (DSO):

"8 Cyl. Ford Cobra 8V Carb"

Ford Special Vehicle Order & Parts Specification (SVO):

"428 Special Interceptor" and "428-8V Special"  (option codes 7393137, 138, 139, 141, depending on transmission and EECS config.) 

Ford Passenger Vehicle Order Card (May 1966)

Relevant options include: (S) - 390-4V 8 Cyl.-Special, (Q) - 428-4V 8-Cylinder, (P) - 428-4V 8-Cyl.-Police Inter.

Notice there's a specific code for the Police Interceptor (P) and it wasn't selected for the Shelby units. -- instead, (S) - 390 Special was selected (with the DSO/SVO detail overriding the selection of order card / computer record): 

Ford Vehicle Invoice to Shelby American:

"428 Inter Engine" (assume 'Inter' is short for 'Interceptor')

[ SHELBY AMERICAN DOCUMENTS ]

Shelby American Press Release, dated August 1, 1966 (referring to the engine in the 427 Cobra - Street Version):

"428 CID Special Police Interceptor Engine with modifications by Shelby American"

Shelby American "Facts" Tri-Fold:

"Ford 428 c.i. engine with Police Interceptor hi-rev cam, hydraulic lifters, and cylinder heads, (middle riser intake manifold and two Holley 600 C.F.M. 4V carburetors.) This is a Shelby exclusive." 

Shelby American "Features" Tri-Fold:

"GT 500 engine; 428 cubic inch Cobra Engine, two 4-V carburetors, special induction"

Shelby American Monroney (Window Sticker) for a Shelby G.T. 500

"Shelby GT 500 with 428 Cobra Le Mans 355 HP Engine"

[ NON-PERIOD / NON-AUTHORITATIVE DOCUMENTS ]

And while not an in-period document from Ford or Shelby, Kevin Marti incorrectly calls the GT500's engine a "428-8V PI Engine", "428-8V Police Interceptor V-8 Engine", "428 PI Engine GT-500" (and similar variants).

Wikipedia - FE 428 engine configurations and applications

• 4V, 10.5:1
• 360 horsepower (270 kW) at 5400 rpm and 459 lb⋅ft (622 N⋅m) at 3200 rpm
• 1966–1970 Ford Police Interceptor
• 1966–1970 Mercury Police Interceptor

In summary:

The '67 Shelby G.T. 500, with 428 FE block, 390 GT cam, aluminum mid-rise 8V intake, dual 4bbl 600CFM BJ/BK carbs, C7AE-A heads (390 version with 14-bolt pattern for exhaust manifolds), and 390 GT exhaust manifolds would have been officially called the "Ford Cobra" (sales) and "Special Interceptor" (engineering) by official in-period Ford documents.

[Brian Styles]

Additional info on this topic provided by Dave Mathews via email:

In 1966, the 428 was merely a bored and stroked 390. The '66 428 PI variant also received the solid lifter cam from the 410 HP 427 and used the MR 427 intake manifold. 

In 1967, the 428 PI received the 390 GT cam.

In a '67 Shelby GT500, I believe the short block would have been the same as a '67 428 PI (428 block with 390 GT cam) with the following modifications and added components that would have made it a 'Special Interceptor':

• C7AE-A heads (with 390 GT style 14-bolt pattern for exhaust manifolds)
• 390 GT exhaust manifolds
• C7ZX 8V intake 
• Dual 600cfm Holley BJ/BK carburetors
• Shelby-supplied "Cobra" valve covers
• Shelby-supplied "Cobra" air cleaner lid

The stock 'Police Interceptor' motor was set up for the full-sized passenger cars and would not fit between the shock towers of a Mustang due to the size of the 428's exhaust manifolds. The 390 exhaust manifolds (and heads with 14-bolt pattern for them) allowed the 428 cu.in. FE to fit between the shock towers in the Mustang platform.  

The configuration of the 390 and 428 cylinder heads are very similar, with the main difference being the exhaust manifold bolt pattern. The heads when used on a 428 in a full-size car had 8 bolts for attaching the exhaust manifolds, whereas the when used on a Mustang 390, or '67 Shelby GT500, the heads had 14 bolts for attaching them.

[Brian Styles]

Received today from Kevin Marti via email

Brian,

I have decided to formally change the description to: 428-8V Cobra Engine w/Shelby Modifications. 

I agree that “Cobra” seems best as a marketing term and “Special” as an engineering term. 

Since the reports are for public consumption, I tend to come down on the marketing side when it comes to descriptions.

A large company like Ford does not speak with one voice.

I appreciate you raising the issue.

Thank you,

Kevin Marti

Marti Auto Works, Inc.

[Rich Plescia]

It seems Shelby didn’t define their G.T. 500's engine name consistently in their marketing materials. Here are some additional names I've found:

• The 1967 press packet (issued fall 1966 / August?) notes Approved Specifications; 
  Engine: “428 CID Special Police Interceptor engine with modifications by Shelby American”
  
  
• The Dealer “10 step” pamphlet (appears to be issued in late October 1966; before the 27^th) notes; 
  The G.T. 500 uses a Ford 428 cubic inch engine with dual four barrel carburetion
  
  
• The Thursday November 10^th, 1966 special guest brochure simply notes; 
  Ford 355 h.p. 428 cubic inch engine powers the new G.T. 500
  
  
• The 1967 Shelby Brochure and the Sales Sheet both note the Engine Specification; 
  G.T. 500: Cobra OHC 428 cu. in. 90` V-8
  
  
• The 1967 Salesmen Feature Card notes; 
  G.T. 500 engine; 428 cubic inch Cobra engine; two 4-V carburetors, special induction