The Cobra Killer, The Mongoose!

gkbikers's 1995 Mazda Miata

Future Miata Mongoose!

Future Engine, Ford 5.0 GT40 from 1997 Ford Explorer 

The Engine Donor

1991 Miata Sub Frame assemblies, front and rear 

The sub frames will be used to begin the transformation of the four cylinder stock Miata to a much more powerful Ford small block V8.  The front K member will need to be cut and rewelded to provide adequate space for the SBF engine.

The Miata engine compartment is quite busy.  After removing the 4 banger and all its associated tubes, hoses, etc., there is actually adequate room to hold the Small Block Ford 5.0.

The genesis of the V8 Miatas began as the Monster Miata.  While the company did go out of business many years ago, the kit to produce the Ford based conversion is still sold and supported by Mr. Martin Wilson of San Marcos, CA.  His web site still carries the name of Monster Miata.   

The Inspiration

The Original Shelby Cobra

The picture below is of an original Shelby, this one a Ford big block 427.

Below is an original 1963 Shelby that ran in LeMans

The engine compartment of the 1963 Shelby which featured the Ford small block 289.  Note that the original AC Ace had a straight six cylinder, so there was more room, front to rear, than the Miata has with its four cylinger.

The original six cylinder from the AC Ace

Two pictures of the AC Ace.  These are NOT Shelby Cobras 

However, Carroll Shelby imported the Ace and then heavily modified it to create the Cobra.

1962 Shelby Cobra

The AC Cobra was a British sports car that was designed and built in the 1960s. American auto racer Carroll Shelby wrote a letter to AC Cars and requested a car modified to accept an V8 engine, a move that set the way for the AC Shelby Cobra. Eventually, the Shelby Cobra would become a successful car in many racing circuits. The fastest production car of its kind for years.  

Carroll Shelby’s concept was simple enough. Take the lightweight, well-proven Ace roadster built by AC Cars and turn it into a world-beating production racer by replacing its aging six-cylinder engine with a lightweight, powerful and reliable American engine: Ford’s new thin wall casting 260 cubic inch V8. At least that was the plan. The AC drive-train would require extensive modifications in the development process.

Fortunately, Shelby’s enterprise began just as Lance Reventlow closed his Scarab shop in Venice, California. Shelby moved his operations as the first Cobra chassis arrived from AC, not only acquiring a fully equipped race car construction facility, but also the services of Phil Remington, whose experience spanned everything from hot rods to USAC Champ cars and whose skills as a fabricator were legendary.

Carroll Shelby had already initiated homologation paperwork with the FIA to make the Cobra eligible for international competition. His goal was nothing less than bringing home to the United States the FIA’s World Manufacturers Championship.

In April 1963, as the Cobra was demonstrating its speed and improving its reliability in American competition, the team quickly prepared two cars for Le Mans that summer. They were the most highly developed of all the early Cobras. Features included Dunlop magnesium wheels with larger fender flares, FIA hood scoops and a 37 gallon fuel tank with a quick release fuel filler. The engines, stated to be “moderate tune,” had four Weber downdraught carburettors.

One team car, entered by AC Cars, managed by Stirling Moss and driven by Bolton/ Sanderson, finished 7th overall, 3rd in the GT category and won the 4-5 litre class. This success resulted in the construction of six more Cobras designated as Le Mans versions by Shelby and built with rack and pinion steering.

330+ hp, 289 cu. in. V8 engine, four Weber 48 IDM downdraught carburettors, four-speed manual transmission, four-wheel independent suspension with transverse leaf springs, four-wheel disc brakes. Wheelbase: 2,286 mm (90")

Source: RM Auctions
Photo Credit: Copyright ACME

Shelby AC Cobra specs per Wikipedia

Mazda Miata, NA per Wikipedia

 If you compare the two cars, you cannot escape the fact that the dimensions are almost identical.  When the conversion of the Miata is complete, the Ford engine and associated running gear (transmission, clutch, rear differential assembly) typcially adds about 250 lbs, about 2/3s of that being on the front axle and the rest on the rear axle.  The weight distribution is only slightly affected and is of no major consequence when the suspension is adjusted and dialed in.

To show that the engine actually does work and fit the Miata, you can go to V8Miata.net to view pictures such as those shown below.  These are cars that have been built by their owners, not by professionals (although these guys have done excellent work, I think you'll agree).

And another shot, obviously a different car