Mailbag: Camshaft, Torque Converter & Gear Ratio Recommendations for an ’86 Mustang Race Car

1986 Ford Mustang GT


You’ve got questions. We’ve got answers. We work with the Summit Racing tech department to tackle your automotive-related conundrums. This week, we’re recommending a camshaft, torque converter, and rear-axle gear ratio for a race-only ’86 Ford Mustang.

Q: I have a 1986 Mustang project car with a 351 Cleveland engine. The four-bolt main block has been bored .040 inch over and decked .010 inch. It has 10.63:1 TRW forged flat top pistons, stock crank and rods, and 4V open chamber iron heads that have been shaved .020 inch. I will be using 1.73 ratio roller rocker arms and a 750 cfm Holley double pumper carburetor on an Edelbrock intake. The car will be a race-only vehicle.

I have not decided on a camshaft yet. I was thinking about either a Lunati solid cam with .598/.612 inch duration or a COMP Cams 306S solid with .640 inch duration. Which would you recommend?

I could also use a recommendation on a torque converter and rear axle gears.

A: Your basic engine combination sounds good, but the compression with the 76.2cc chamber head and flat top pistons is closer to 9.25:1 than 10.63:1. That is not enough compression for a strictly race-only vehicle.

For a 9.25:1 compression 351 Cleveland, COMP Cams recommends a COMP Cams Magnum hydraulic camshaft. It has 236 degrees of duration at .050 and .570 inches of lift. The powerband is from 2,000 to 6,000 rpm, and COMP recommends a 2,500 rpm stall converter.

As for rear axle gears, go with a 4.56, 4.88, or 5.14 ratio depending on how tall a tire you can stuff under the Mustang’s rear fenders. The taller the tire, the more gear you can run.

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