A new combination of an MP...
A new combination of an MP R3 engine block and W-9 heads makes this 340 a powerful replacement for your tired old engine. (Surgeon General's Warning: Installing this engine in your car may cause an increased heart rate and adrenaline flow.)
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.
The new R3 block has the lifters...
The new R3 block has the lifters at 48 degrees as opposed to 59 degrees. This means a better pushrod angle and a high-revving engine that lives.
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 11/42-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.
 The four-bolt main R3 block...  The four-bolt main R3 block was strong and was checked for bore, deck, and main-journal dimensions before assembly. |  JMS installed a forged 318,...  JMS installed a forged 318, six-bolt flange crankshaft with a 3.31-inch stroke and a 318/340 main journal size. |  JMS had to drill oil galleys...  JMS had to drill oil galleys in the lifter holes because there were none. Chrysler sells the jig to do it, insuring proper oiling. |
 The pistons are custom-made...  The pistons are custom-made pieces from Ross and are connected to Eagle 6.123-inch rods. |  The bottom-end build was uneventful,...  The bottom-end build was uneventful, and we moved on to the middle stick. The custom-ground Comp Cam's camshaft profile was .631 intake and exhaust, with .260/.260 duration at .050 on a 108 lobe center. The lift on the lobes was high enough, but extra care was needed to install the cam without nicking the bearings. |  With the addition of the Milodon...  With the addition of the Milodon oil pan, the bottom end was complete. |