Q&A

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

 
1986 Ford Mustang GT

(Image/AllFordMustangs.com)

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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