Small Package, Big Surprise: 600+ HP from a 340

What do you call a small-block 340 that can develop 602 hp at 7,000 rpm on 91-octane go-go juice? Impressive comes to mind.

The idea for this project was to put together a streetable package by replacing a tired small-block with something to really brag about. The goal was to make 2 hp per cubic inch with a normally-aspirated motor on 91-octane pump gas. As far as we know, this engine combination has never been built before, so Mike Johnson of JMS Racing Engines in Monrovia, California, set out to do just that for customer John Copeland.

The new Chrysler R3, 340ci block and W-9 Chrysler heads (the heads used in Winston Cup and on Sprint Car engines) were purchased from Lawrence Roundtree at Mopartsracing.com. Because this combination is new, there were more than a few glitches to overcome in developing the package. Although 90 percent of this motor is available in the Mopar Performance catalog, when you're breaking new ground, some parts are not available, and no one knows how it will all fit together. This is where JMS's experience proved invaluable.

It's All in the Angle

Chrysler developed the R3 block because, traditionally, their blocks have 59-degree lifter angles, making it difficult for a high-rpm valvetrain to survive. The R3 block has the lifters at a 48-degree angle, giving a better pushrod angle. To begin with, our block (PN P4876672AB) was completely blueprinted. JMS drilled the oil galleys in the lifter holes because there were none there. Chrysler sells a jig to properly handle this task, but we're not sure why they don't drill them at the factory.

JMS also drilled oil drain holes at the top of the engine block, in the valley area, because without them, the oil would have to travel over a 1/2-inch-tall wall to reach the existing holes before it could drain back to the oil pan. This could effectively leave a quart of oil suspended up there at all times.

Because Chrysler moved the intake ports on the W-9 head to get the pushrod alignment straight, offset lifters needed to be used. JMS used a combination of centered, left, and right offset lifters. Neither Chrysler nor Comp Cams could clearly state what lifters were needed for this combination, but when it did come time for lifters, Comp was the only company that had offset lifters in a Mopar diameter. Each lifter had to be checked individually for geometry to see what offset was needed. Once the correct lifter offset was established, Comp Cams had to figure out what tie-bars were needed to connect the lifters. "Chrysler didn't know what lifters to use," said Mike. "They were on the phone with us asking what we came up with. That is why this motor is so cool. It's so new that even Chrysler is interested in what it took to put it together." The combination of lifters consisted of eight Comp Cams centered lifters (892C-1), four of the left offset lifters (892L-1), and four of the right offset lifters (892R-1). Eight Comp Cams link bars (CC814) hold the lifters together.

Getting to the Bottom

The forged 318, six-bolt flange crankshaft (PN P5249135) has a 3.31-inch stroke and 318/340 mains. Custom made Ross pistons were connected to Eagle 6.123-inch rods (356-CRS6123C3D). Working with Comp Cams, Mike calculated the custom grind camshaft (20-999-3) profile to be .631/.631-inch lift, with a .260/.260-degree duration at .050 on a 108 lobe center. The valvesprings were Isky (PN 9385) with matching titanium retainers and 10-degree locks. "You have to run a roller cam because of the offset lifters," Mike said. "You cannot buy an offset flat-tappet lifter. There are enough small roller cams available to make it streetable. This one may not be a grocery getter, but it is streetable."

The new W-9 aluminum cylinder heads (PN P5007066) only needed minor port work. Mike just knocked off the flashings and shined up the ports; there was no extensive work done. The heads, which feature a 50cc combustion chamber, were that good right from the factory. Manley custom-made the valves with 2.100-inch intake and 1.600-inch exhaust. The rocker setup is made by T&D for Mopar Performance. The pro race rocker-arm assembly (PN P5007470) was preset and included the shafts and bolts. The pushrod length had to be calculated. Manley supplies them off the shelf in increments of 0.050 inch over stock.