Although Andy can cut piston valve pockets with the short-block still in the car, it is not a cost-effective procedure unless the heads have to come off to install a ported set. For this test, we left the pistons stock, and installed Sean Highland Motorsports (SHM) 2730 cams. This is a 230/230 by 114 LCA grind that delivers 0.495-inch lift. Back on the chassis dyno, we found the cams to be worth power from about 3,800 on up, with the peak output increasing to 215 hp at the tires. At the track, another goal was reached in that we went under the 9-second mark for the eighth-mile. The timeslip now read 8.86/80.20 mph.
Shortly after this, we installed a used PI intake from the later '99-04 engine. This resulted in 228 rear-wheel horsepower and 8.54/81.7 at the track. This was now a car capable of running high 13s in the quarter, which made it at least passably respectable in Mustang circles.
Heads And Long Tubes
We have gained some 46 hp at the wheels, and exhausted most of the cheap mods. Now it's time to port the heads, add a little more compression by milling them, and installing some long-tube headers. The heads were ported by Andy, but he normally orders CNC items from DSS for his customers. One thing about ported heads that is worth pointing out here: In stock form, the Mod motor's valve-seat geometry is good. As a result, ported heads only deliver a significant flow increase at higher valve lifts. Early cams have some 0.470-inch lift, where the PI cams are 0.510-inch lift, significantly better as they have access to the increased flow potential of a well-ported set of heads. The trick for real power increases with a mod motor is to install heads in conjunction with high-lift cams. We already had the Sean Highland cams, so we were reasonably good in that department. On the exhaust side, the shorty headers were more of an installation convenience and had sacrificed some flow, so we replaced them with a set of long-tube headers. Here, Andy recommends the new Edelbrock merge-collector long tubes. On the chassis dyno, we saw a very satisfying 38hp increase, but the real fun was yet to come.
Manifolds, Cams, And Carbs
Now is the time for serious power moves. In this segment, we eventually replaced the PI fuel-injection intake with an Edelbrock Victor Jr. manifold and its associated MSD ignition conversion-all as a kit under Edelbrock part number 2839. This is a single four-barrel intake and uses a 4150-series Holley carb. For our initial test, we bolted a box-stock 650 HP Holley. With the injection gone, we needed a means to program an ignition curve, and fire the original coil-over-plug setup.
The MSD electronics that come with this kit do just that.
Before bolting on the heads, a cam change was made. Earlier it was pointed out that valves can come in contact with pistons if the duration is too long, or the LCA is too tight. Without piston cuts, a critical decision must be made. Should you compromise on duration (i.e. use less) but run with the optimal LCA, or should you compromise the LCA (run with a wider than optimal one) and use more duration?
At this point, we contacted Lunati, and found that they were already working on a new line of cams for Mod motors, so our project car quickly became a vehicle for testing them. The plan was to test three similar dual-pattern cam designs (236/242 at 0.050) on 114, 111, and 108 LCAs. Even with our home-grown fly-cut pistons, the 108 LCA put the valves closer than was safe, so only the 114 and 111 LCA cams where tested.
Tune up ace, Aaron Lail of...
Tune up ace, Aaron Lail of Tru Dyno Sports, set up the stock '97 vintage mod motor to deliver all the power that Ford intended of it. This thing needed the automotive equivalent of Viagra.
This is the factory "Performance...
This is the factory "Performance Improved" intake, or PI for short. It's appreciably better than the pre-'99 factory intakes, but it is still hard to imagine anything more tortuous in the way of runner passages.
It's entirely practical to...
It's entirely practical to cut valve pockets in mod motor pistons while the motor is still together, however, it is not cost effective unless ported heads are installed at the same time.
Here is what a fly-cut stock...
Here is what a fly-cut stock piston should look like when it's done right. The intake notch is on the left.
If you are building a new...
If you are building a new short-block, these super tough pistons with "big cam" valve reliefs from DSS will get the job done without crashing the budget.
There is flow to be gained...
There is flow to be gained from a good porting job, but the extra flow only becomes significant from about 0.350- to 0.400-inch lift. This DSS CNC head shown here will flow a lot more air than a stock head, but needs to be used with a high-lift cam. Our heads were ported by hand, but are similar in flow to the DSS.