Mopar Small Block - Less Is More

In these tough economic times, we all have to compromise a little. Many folk's 401(k)s are now 201(k)s, and the cubic dollars that fed the automotive aftermarket have dwindled. Enthusiasts are stretching to make every small dollar buy more goodies. In a parallel line, many engine builders, like Brett Miller of BH Performance, are discovering the secrets that stretch the power from small cubic-inch engines into big-block territory.

Brett's been a Mopar guy since birth. You see, his pop drove him and his mom home from the hospital in their '67 Barracuda fastback just after he was born. Poor guy didn't stand a chance to be anything but. When he decided to enter the ring with some of the top engine builders in the country and compete in the Jegs Engine Masters Challenge, he didn't hesitate to make his entry a version of the legendary small-block 340. Taking the best of the 318 and 360 engines, the 340 has always been known as a big-bore, short-stroke, high-winding rev-turner. It would surely make good horsepower, but would the design lend itself to making the torque necessary in a contest where the dyno pull starts at 2,500 rpm and shuts of at 6,500? Read on. (Hint: the answer is "yes.")

A derivative of the 273ci LA engine, the 340 first showed up in late 1967 for the '68 model cars, and immediately began beating up on the big-blocks. It was especially effective in cars destined to actually make left and right turns instead of just a straight line down the strip. Unlike the 273 and 318 blocks, the 340 used a big bore. Actually, at a 4.040 standard bore, the 340 is a bit bigger than even the 360 engine's 4-inch bore.

The block that Brett used was a vintage piece that was in good shape and cleaned right up at 0.030-over with a torque-plate hone. A torque-plate bolts in place of the cylinder head when machining the block, and typically would distort the block a good amount as it simulates the stresses that the head bolts pass onto the block. The four head bolts on a small-block Mopar surrounding the cylinders, though, are actually spaced far away enough from the cylinder that the distortion seen is not quite as bad as on Chevy stuff. There is still pinching all around the top of the cylinder as the armor ring of the head gasket is compressed, making the use of a torque plate a requirement in any high-performance build.

Brett's crank for the engine was a 4340 forged steel piece he picked up from Eagle Specialty Products. Their forgings in small-block setups like this have been used in many applications well over 700 hp, so Mr. Miller was pretty confident he would have no problems. In addition to the big 0.125-inch radius fillet that makes the crank so strong, Eagle's optional ESP Armor finishing on Brett's crank helped reduce stress risers and created an ultra-smooth, oil-shedding finish on the shaft. He had never used the ESP Armor finish before, but was totally sold after checking it out. He even ordered the finish on the ESP H-beam rods used in the project. Brett told us: "I think it's amazing! That stuff really toughens the finish up. It's a lot nicer finish on everything after it's treated. The journals, everything, just a much nicer finish. Even on the rods, when you pick them up in your hands they just feel better. If that makes sense." For the claim that it was oil repellent, Brett was equally surprised. "On the counterweights, whenever it got oil on it, it just beaded up. It's definitely weird. It's very slippery and I don't know exactly what the process is, but it definitely made it harder. I'm a believer."