Small-block Mopar engines are easily identified by numbers cast into the side of the block
When the engine was reinstalled on the dyno, it underwent a dramatic personality transformation. Peak torque rose from 305 lb-ft at 2,500 rpm to 343 lb-ft at 4,000, and horsepower jumped from 187 lb-ft at 3,750 rpm to 301 at 5,000. Of equal significance was the broadening of the torque curve. Whereas the stock engine's torque curve dropped below 300 lb-ft at 3,000 rpm, the rebuilt 318 produced over 325 lb-ft from 2,500 to 4,750 rpm. A torque curve like that is just what's required for strong street performance or hauling heavy loads.
Next, Andy installed a camshaft with .234 degrees of exhaust duration at .050 lift and two degrees wider lobe separation (112 versus 110). His intention was to broaden the torque curve and increase top-end power without seriously degrading low- speed performance. As fate and the dyno would have it, that's exactly what happened. In fact, the cam change produced results that were better than anticipated. At 2,500 rpm, torque increased by 21 lb-ft, and peak torque rose to 370 lb-ft. Horsepower now peaked at 324-an increase of 23. Horsepower remained above 310 all the way to 6,000 rpm.
The most impressive aspect of this combination is, aside from the camshaft and valve gear, all the parts were of the stock or stock-replacement persuasion.
In the first test, we used a Comp Cams 270H grind with .224/.224 at .050 duration and .470
As is usually the case when changing components that affect the amount of air an engine can process, when an alteration eliminates one flow restriction, another becomes the factor that controls horsepower. With the second camshaft in place, the cylinder heads became the "cork" in the system. Andy's corkscrew was a pair of ported 360 heads with Mopar Performance 2.02- and 1.60-inch valves. These castings are similar to Mopar Performance's PN P5249574, an alternative if suitable used heads are not available.
With the 360 heads bolted onto the short-block, horsepower and torque ratcheted up another notch; this time, the peak readings were 381 lb-ft at 4,250 rpm and 346 hp at 5,250. Again, torque was up at all test points, with the engine now making at least 360 lb-ft, from 2,500 to 5,000 rpm.
For the final test, Andy installed a modified 750-cfm Thermo-Quad on a matching cast-iron intake manifold (which had a bit of clean-up work done on the inside). This paid off with a slight increase in low-end torque and 11 hp at the peak. The engine now produced 388 lb-ft of torque and 357 hp. Compared to the stock engine, the overall improvement was 83 lb-ft and 165 hp.
The dyno numbers only tell part of the story. After Mickey installed the engine in his '67 Barracuda, he took it to Silver Dollar Raceway in Reynolds, Georgia, for some real-world testing. Using the same Hedman headers used on the dyno, a 3.55:1 ring-and-pinion set, and a 3,000-stall torque converter, the 'Cuda cranked out a 12.76-second e.t. with a trap speed of 103.02 mph. On the street, the engine is deceptively docile and idles well at 750 rpm.
The low-cost approach also extended to the ignition system. A stock electronic distributor
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This photo shows how the PN 75110 headers exit by required cutting of the inner fender, he
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All stock A-engine connecting rods are 6.123 inches long, center-to-center. This 318 conne
Hot off the dyno, with only slightly modified cast-iron heads and intake manifold, this 31