SO CLOSE!

Our ’94 SC Lays Down 387 RWHP—Here’s How

As part of the new cylinder head package, Dalke replaced the original 1.78/1.45 valves with severe-duty stainless 1.90/1.60 valves for increased breathing.

Yoe’s Cylinder Head Specialties manually stone-ground the valves for improved seating and flow. This sort of handwork is becoming a lost art, and it was pretty cool to see it done.

A gentle 0.004-inch decking of the heads altered compression slightly, but made for a much better seating surface on the porous stock head castings.

In our last article on this ’94 Supercoupe, we ran into extreme boost levels in our quest for horsepower from the little supercharged V-6. With the Magnum Powers MPx supercharger clearly capable of more airflow than we could support (boost climbing north of 23 psi), it made sense to work on the heads-and-cam combination to better deal with some of that boost.

Measurement revealed a modified chamber size of 59 cc. This change, and the decking, resulted in a change of compression ratio from 8.5:1 to 8.85:1.

Seen in a stock head, here you can see how shrouded the larger 1.90-inch intake valve really is.

In addition to the porting and polishing, Dalke cleaned up the combustion chamber to reduce that shrouding—the difference is dramatic.

This new SuperCoupes Unlimited cylinder head package employs 1.90/1.60-inch valves, and returns an intake flow increase of about 40 percent and an exhaust flow increase of nearly 70 percent (over stock). Dual springs were specially chosen to provide ample seat pressure to handle high boost levels while providing plenty of headroom for the 0.580-inch lift from the custom-grind Comp Xtreme Energy cam. The intake manifold receives special attention to the radius diameter of each cylinder port entry and is port-matched to the heads. Other valvetrain hardware includes Scorpion 1.73-inch roller rockers and Trick Flow 0.080-inch-wall pushrods.

The business end of the port-and-polish job reveals a major improvement over the stock intake ports.

The job entails too many steps and details to list here, but here are a few pointers that will help get you on your way with minimal trouble:
• Take time to clean all intercooler connections carefully, and re-seal with RTV or Teflon sealant specifically designed for the job. Vacuum leaks will spoil your day, so don’t take any chances. Also, take time to properly align the tubes when you are done. This is time well spent.
• Leave the SC top, throttle body and inlet plenum on the blower. You don’t want to get any trash in the blower, so the more covered up it stays, the better. It can all be removed as one unit, saving time and effort.
• Removing the power steering pulley to access the accessory brackets is a pain. Instead, use a 3/4-inch step drill to put a hole in the right spot so you can get a socket on the bolt behind it.
• Take time to clean all the parting lines around the timing cover and intake manifold prior to removal. We can’t emphasize enough the importance of keeping things as clean as possible. Any time a motor is opened, there is serious risk of trash getting into the oil pan, oil pump and subsequently the bearings. This was the case with this motor, which showed severe bearing wear and oil pump damage that required replacement. We were lucky to have caught it in time, as all the bearings were worn through to the copper linings.

Similar improvements in runner flow and volume are obvious in looking at the exhaust ports. Note, too, the new bronze valve guides.

• To avoid breaking the timing cover, don’t miss the hidden 6mm Allen bolt behind the oil pump on the lower driver-side corner, and typically the long water pump studs that go through all the way to the engine block usually want to stay stuck in the block. Always remove them before attempting to break loose the timing cover.
• Some water will end up in the oil pan after the timing cover is removed. Antifreeze is death to bearings and other wear points, so the less you get in the motor, the better. A good way to minimize the amount of water getting into the motor (and all over the floor) is to use a small siphon bulb to suck the coolant out through the water passages in the front of the block before removing the cylinder heads.
While the heads were off, and before removing the cam and lifters, we took the opportunity to remove all the carbon from the tops of the pistons and installed the ARP head studs. With the motor dry and free of oil, we pulled the cam and lifters, pre-oiling them as we assembled everything. The cam doesn’t require special lubrication, because it is a roller design, but we use general assembly lube just to make sure no dry spots exist during initial start-up.
Cam install is straightforward, but there are a few things that are extremely important. It is necessary to remove the woodruff key, and the small spacer ring that resides behind it, from your old cam. It will look as if it is part of the cam, but it is not. Swap the spacer ring and woodruff key onto the new cam before installing.
Checking the cam centerline with a degree wheel is the best practice because of variations that can occur not only in the cam but in the timing chain, too. While SC timing chain sets do not offer adjustability, it is good to know where you are when analyzing your results. In our case, we came in just one degree retarded from spec, so we left it as ground.

The cam is a custom Comp grind matched to the heads and the blower setup. It features 0.570/0.580-inch lift and 218/224 degrees duration.

With any non-adjustable valvetrain installation, care must be taken to verify lifter preload and valve-stem-to-rocker-tip alignment. The 3.8-liter valvetrain geometry favors a higher-sitting rocker arm, so, when given the choice, it is preferable to run a slightly longer pushrod and shims versus a shorter pushrod and no shims. We used 7.300-inch-long pushrods and a 0.015-inch shim to get the desired preload, but individual results will vary, so always check. When possible, it’s best to check preload with the intake manifold off so you can see the plunger action as you tighten down the rocker.

Like the heads, the intake manifold is the stock casting because nothing else is available. But Dalke cleaned up the ports to better match the heads for better transition and a bit more power.

Scorpion roller rockers (in the original 1.73:1 ratio) replace the factory rockers and free up some extra power. That, and they look cool—it’s a shame to cover them.

Actual reassembly of the engine began with Dalke inserting the cam into the block. He previously replaced all the cam bearings. Make sure you don’t forget the assembly lube!

Before installing the cam retention plate, be sure to lube the side that will face the cam.

Lube one side of this spacer and install the lubed side to face the cam plate.

As always, be sure to align the dimples on the timing chain gears before installing them.

The timing set slid into place with just a few gentle taps from a rubber hammer.

Because of the invasive nature of a cam install and the extreme loads that will be seen from a valve-spring upgrade such as this, priming the motor should be SOP. Always remember to drain and replace your oil first so as not to pump coolant or trash into the motor. Use a strong 1/2-inch drill to bring full pressure long enough to get oil from each rocker arm. You should see 80 psi on a mechanical gauge during this process.
Since it is necessary to remove the harmonic balancer during this process, you must assess the condition of the balancer and consider possible replacement. In our case, we already had a solid-steel BHJ balancer. In any event, to avoid damage, always use the proper tool to install a balancer. A hammer and a block of wood are not the proper tools.

It’s a good idea to apply some RTV around the coolant passages in the water pump gasket, and to the base of the gasket as well.

The SC’s water pump, timing chain cover and oil filter boss may now be installed as a single assembly.

Startup was uneventful, as the car had been previously tuned for the 60-lb injectors. The only necessary change to the tune was to raise the idle level slightly, to 800 rpm. Vacuum was looking good at about 13 inches of Mercury and a mild lope, so we let the motor get up to operating temperature to heat-cycle the valve springs, and then shut it down. This is also a good time to remove all remaining air pockets from the cooling system and check for leaks of any kind.
Test day started off with a quick pull through the rpm range, which showed the motor being hungry for more ignition timing than what it liked previously. We added 6 degrees timing throughout most of the range, and even more in the lower areas of the spark map. The final settings resulted in several runs with around 425 lb-ft of torque and 385 RWHP (SAE corrected). While these were respectable numbers for a mild street V-6 on pump gas, they were not the numbers we were looking for—we wanted over 400 RWHP!

This engine will see some pretty high boost levels, so Dalke used ARP head studs. He applied oil to the threads to prevent galling before installing them in the block.

Good head gaskets are crucial on any SC, as they are prone to failure. They’re even more important in high-boost applications, and Dalke recommends using Fel-Pro MLS gaskets for a ’98 Mustang (PN 9262 and 9263). Owners of early-model blocks should use some copper gasket spray on the gaskets; late-model blocks are fine without it.

After installing the heads, Dalke liberally coated the ARP hardware with the included assembly lube.

Prior to installation, each lifter needs to be thoroughly coated in oil.

More grease coats the tip of each pushrod and valve to prevent wear on initial startup.

Installation of the roller rockers completes the valvetrain.

Before installing the intake manifold, it pays to lay some silicone at the intersections of the block and the heads.

The headers are the same stainless shorties that were on the car when we bought it. They’re currently unavailable, but Kooks makes excellent mid-length and long-tube headers for the SC. Remember to install the dipstick before the driver-side header!

That’s as far as the motor should be assembled before reinstalling it in the car—removing the engine from the car isn’t even necessary for these upgrades, but it will make the job easier.

Prior to reinstalling the engine in the car, Dalke installed a cam synchronizer assembly (it’s what the SC has in lieu of a distributor), turning it with an electric drill to prime the oiling system.

Here’s another cool trick. The larger A/C condenser is the stock unit; the smaller one is from a Bronco II. It will fit without much effort and won’t block air heading to the intercooler, making that piece more efficient.

A previous owner fitted this car with a BHJ balancer—that’s good, but the BHJ doesn’t have as many timing marks as the stock piece. Trace the machined marks and use them to set initial timing at 26 degrees.

If you’ve set timing and installed the cam synchronizer correctly, placing a razor blade across the distributor will put the razor exactly in the middle of this cut.

If you have a stock clutch, now is a good time to upgrade. This aftermarket clutch may look dirty, but its friction surfaces were in great shape, so we reused it.

Installation of the engine would take more space than we have here, so we’ll skip straight to the chase. The car now has a definite lope at idle that makes it sound mean, but as the rpm climb, all you hear is the high-pitched whine of the MPx blower.

During testing we observed boost climbing and power falling off early, which is a sure sign of a remaining restriction—exhaust. It seems that the dual 2.25-inch pipes simply are not large enough to accommodate the airflow/exhaust we have generated with this engine combination. Now it is the right time to retire the older shorty headers and look at a more modern Kooks long-tube setup. But that is another story for another time, as we continue to build the output of our Supercoupe.