Power Puzzle
To most Mopar aficionados, performance starts with a V8. You know-one horsepower per cubic inch, a lopey idle, and a mechanical staccato of 16 valves heard through a pair of full-length headers. If these are primary factors in your engine buildups, our venerable 225ci Slant Six may not be your cup of joe. At first, it wasn't ours either.
In fact, one of our toughest decisions was whether we should keep the Slant Six that came in our Project D150, or replace it with a Mopar Performance crate engine. Part of our decision involved the abundance of Slant Sixes in existence. Yes, these Leaning Towers of Power are as common as the vehicles they came in. As a result of typical hot rod ingenuity, many Slant Sixes have been replaced by Mopar V8s. Somewhere-perhaps in your garage-sits a Slant Six just begging for attention.
By no means were we going to build a multipurpose, fire-breathing, Hemi-eating six-banger. No, we simply wanted to up the performance for great street cruising and an occasional bark of the tires. This led us to our final concern-show appeal.
The engine, destined for our Project D150, needed "wow appeal." We could easily double the horsepower, but could we build a clean, sharp-looking engine?
By using a variety of parts from several suppliers, such as Mopar Performance, Crane Cams, JE Pistons, Holley, MSD, and others, you will see how our DeskTop Dyno-projected, 237hp Slant Six was built. Once the combination is installed completely, we'll stop by our favorite chassis dyno, and give it a chance to perform.
Follow along with us as master mechanic Dave LaForce takes us through the steps to build a potent Slant Six that has major appeal for show duty.
 The block and crank were sent...  The block and crank were sent to Owenby, a local machine shop, where the block was bored .040 oversize and the crankshaft was polished. LaForce began assembling the engine by installing the brass freeze plugs. |  A fresh set of Federal-Mogul...  A fresh set of Federal-Mogul cam bearings were installed with a cam bearing installation tool. LaForce was extremely cautious that all oil holes lined up, to prevent any lube problems. Due to the extent of this rebuild-in which we replaced many of the components in the rotating assembly-we took the engine to have it balanced. A "poor man's" rebuild probably would have skipped this step. |  Here you can see the Slant...  Here you can see the Slant Six-specific offset in the rear-main cap seal. After a dab of silicone on each of the mating ends, they're ready to go together. |
 LaForce installed the Hastings...  LaForce installed the Hastings Rings, and then, using a standard ring compression tool, prepared the combination of JE Pistons and the stock, reconditioned connecting rods for installation. |  Using a dead-blow hammer,...  Using a dead-blow hammer, the JE Pistons (PN 157775) were put into place. We arranged for JE Pistons to custom-make those forged, lightweight, .040 oversize pistons, with a 10:1 compression and zero deck height. This changed the displacement of our Slant Six to 231ci. |  LaForce installed new Federal-Mogul...  LaForce installed new Federal-Mogul bearings, then installed the caps, ensuring that the cap locks lined up. |
 To ensure proper tightness,...  To ensure proper tightness, LaForce adjusted the connecting rods to 45 lb-ft of torque. |  Applying the pre-lube that...  Applying the pre-lube that is included with the cam is recommended on non-pressure feed areas. Oil was applied to all cam bearings. |  Crane Cams custom-ground a...  Crane Cams custom-ground a cam to meet our specifications. With 10:1 compression, this cam is designed to prevent pre-ignition, and still maintain good street performance. Our new PowerMax(tm) Series cam gained a part number in the process (PN 72H000002) and has a duration of 216 degrees at .050-inch valve lift for the intake, and 220 degrees at .050-inch valve lift for the exhaust. Total lift is .454 inches for the intake and .467-inch lift for the exhaust. |