Fast Fox Body: The Inside Story on the Stillborn ZR-1 Killer

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Roush 25th Anniversary Special 5.8L Twin-Turbo 1988 Ford Mustang

One of the last things I worked on before leaving Roush was a 5.8L Twin-Turbo 1988 Mustang. Ford’s then SVO (Special Vehicle Operations) group commissioned the car. They had learned about Chevrolet’s plans to introduce the Corvette ZR-1. Rumors put the price of the new Corvette variant at about $60,000. It was rumored to be one of the fastest production cars of its time. SVO wanted to sell this Mustang for $30,000, and have it fast enough to outrun the ‘Vette. This ZR-1 killer was also going to be the 25th Anniversary Special.

The teardown revealed six teeth missing from second gear. I had someone in the car with me who verified I didn’t miss the gear. The T-5 just couldn’t handle the torque.

We built the car in a very short period. To save time, the engine wasn’t dynoed, but 375 hp/390 lb-ft is a conservative rating. All that grunt was shoved into the car with a T-5 transmission. The production plan was to use a T-56, but there wasn’t one available for another year or so.

The T-5 wasn’t up to the task. One time I did a WOT from a standing start. At 5,000 rpm I sidestepped the clutch, scurried up first, grabbed second, dumped the clutch, and started to floor it again.

I made it about halfway down when there was a loud BANG and I had no power going to the wheels. I coasted about a half-mile right back into the shop. The trans locked up as I was coasting through the doorway. The teardown revealed six teeth missing from second gear. I had someone in the car with me who verified I didn’t miss the gear. The T-5 just couldn’t handle the torque.

If this was the car that was going to mark the Mustang’s silver anniversary, it was going to do it in a blur. It ran a low 12-second quarter-mile, and it couldn’t hook up until just before the 2-3 shift. I put the first 2,000 miles on the car developing the tune. By the time I was done, the doors didn’t fit right. The chassis had twisted. The Fox body, even with all of SVO’s chassis stiffeners, wasn’t up to handling that much power. I believe that’s why this car never made it to production.

During the development process Jack Roush asked to drive the car. After his drive, he came to my desk and asked me if I was crazy enough to ride with him in the pouring rain. I asked if I really had a choice. He said “no”.

Because 25 years have passed, I believe the statute of limitations has expired, so I can tell you the next part: We were driving the 25th Anniversary Special in a rain that was so hard I often couldn’t see the end of the hood. Jack took me for a ride on an expressway demonstrating an engine miss at 100 mph. I told him if he got me back alive I knew how to fix that. He did, and I fixed it.

This car still exists. It is in the Roush Museum. I visited the museum several years ago. The boosted Mustang was in a line with other cars. It had a small plaque showing that it was a 5.8L Twin-Turbo. I filled in all of my own memories.

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