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 As a result of typical hot rod ingenuity, many Slant Sixes have been replaced by Mopar V8s.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.
Crane Cams supplied lifters...
Crane Cams supplied lifters with the PowerMax(tm) cam. Prior to installation, each lifter was lubricated on the sides, but only with oil. The bottom will come in contact with the pre-lube on the cam.
We installed a new Mopar Performance...
We installed a new Mopar Performance oil pump (PN P4286740) and a Milodon remote oil filter adapter (PN 21560 and 21566) to help keep our engine clean. The original filter would have been upside-down.
After installing a new Mopar...
After installing a new Mopar Performance timing set (PN P5249636), Dave put the timing chain cover in place. The cover, as well as most of the other smaller parts around the engine, was powdercoated with Eastwood's Hot Coat Powder Coating System.
We replaced the old head with...
We replaced the old head with a ported head from Mopar Performance. This head comes fully prepped with 1.70-inch-diameter intake and 1.44-inch-diameter exhaust valves (PN P4529821). Before installation, and because of our higher cam lift, we had the top of the valve guides milled to prevent any damage. Here, Dave lowers the head into place.
As the head was lowered into...
As the head was lowered into place, the bypass hose was also installed. It is far easier to deal with this hose when setting up either the head or the water pump.
Dave torqued the head to 70...
Dave torqued the head to 70 lb-ft by starting from the middle, and working his way to the outer ends, in three to four rotations.
New Mopar Performance pushrods...
New Mopar Performance pushrods were installed, then the rocker shaft assembly was set in place.
We thought the installation...
We thought the installation of our Hooker Header (PN 5834-1) would be a breeze, but it became a bit complicated. We put the header on the engine and the EGR heat transfer adapter on the intake, then tried to mount them onto the engine separately. We ended up removing the header and intake, assembling them off the engine, and installing the two parts as a single unit.
Since we had such a hard time...
Since we had such a hard time installing the header, we didn't want to take a chance that the bolts would come loose. To prevent future leaks, we used a set of Stage 8 Locking Fasteners.
To prevent damage, LaForce...
To prevent damage, LaForce installed the harmonic balancer with the proper installation tool. Using a hammer isn't recommended-it could ruin the balancer and thrust bearing, as well as gall the snout of the crank.
After installing our Holley...
After installing our Holley 350cfm two-barrel carburetor (PN 0-7448) on the Mopar Performance aluminum intake (PN P4529115), the manual choke is removed and replaced with an electric version.
LaForce tested for possible...
LaForce tested for possible clearance problems between the K&N air filter (PN 60-1260) and carburetor linkage. Without difficulty, the filter was removed to prevent damage during installation.
MSD 8.5mm wires with wire...
MSD 8.5mm wires with wire organizers were connected to our new Mopar Performance distributor (PN P3690788).
We were uncomfortable with...
We were uncomfortable with the clearance from the header and the oil pan. Although it would have been easy to make an adjustment, we removed the oil pan-as shown here-and made a small indentation. This gave us about 2 inches of clearance between the header and the oil pan.
After installing the motor...
After installing the motor mounts, we were ready to put the engine back into the truck.