1965 Ford Mustang Convertible Gets 331 Ford Small Block
Disguised As A Stock 289, This Stroker 331 Ford Small-Block Makes Well Over 400 Horsepower
Feeding The Beast
Getting enough air and fuel into a 331 cubic-inch engine would normally require a overly healthy, choppy idle camshaft that might give away the true secret of this stock-looking engine. But with a cylinder block that's set up to use a roller camshaft, J Bittle American's use of a Ford Racing E303 hydraulic roller camshaft and lifters will keep the engine well fed while maintaining a smooth yet performance-like idle. The cam features 220/220 degrees of duration at .050 lift and uses .498/.498-inch of valve lift on a 110-degree lobe separation angle.
The AFR aluminum cylinder heads also received some light porting and port matching, but J Bittle American engine expert J.R. Twedt says that aside from the extra porting, the AFR cylinder head is one of the best performing street heads in the industry and is perfect for this application. Tony Mamo of Air Flow Research concurs and adds that the 165cc heads work well in this application, flowing 250 cfm to make them more than capable of producing power in the mid to high 400 horsepower range. Mamo also suggested that if we wanted to squeeze a bit more out of the engine, the 185cc head might be worth another 30 or more horsepower.
In designing this engine combination, Twedt also decided to use an Edelbrock RPM Air-Gap intake manifold, as it has excellent fuel distribution and runs cooler to provide a more dense air charge with its raised runners and plenum. But while it might be great to show off a set of aluminum aftermarket pieces like these, the goal here was stealth. In this case, the names on both the cylinder heads and intake were machined away. To further add to the engine's stealth, after it was assembled, the team at JBA painted everything Ford black to match the correct engine color for Peck's '65 Mustang Convertible.
Big Power, Small Package
Because the engine was to remain as stock-looking as possible, the factory Autolite 4100 carburetor was used during the engine's break-in and initial dyno tests. The Autolite four-barrel carburetor is Peck's original equipment on the '65 Mustang and it was in perfect working condition. Even though the carb is estimated to flow about 450 cfm, it allowed the 331 to crank out nearly 400 horsepower on JBA's DTS engine dyno.
By adding 36 degrees of total advanced timing from the PerTronix electronic distributor and outfitting the Autolite carburetor with 68/78 jets and a 6.5 power valve, the engine managed to achieve 418.5 corrected horsepower at 6,300 rpm and 392.9 corrected lbs. ft, of torque at 4,500 rpms. This stock-looking 289, which originally made 225 horsepower, now packs a big punch that will leave many people wondering how they got beat by a "restored" 289 cubic-inch small-block in a '65 Mustang.