Road Race Mustang Engine Build - Iron Lung

Besides building torque, the savvy American Iron engine builder is looking for ways to restrict horsepower. That way, an engine can be built with plenty of torque and a little too much horsepower, then the horsepower can be squelched somehow. Initial attempts at this by AI competitors were fairly lame, including pinching the exhaust-pipe tips (doesn't help) and fitting cheap, low-profile air filters (kills 20 hp). Now the wet rag is applied electronically by tuning the engine management to pull timing at higher rpm. This is more accurate, allowing maximum torque and allowable horsepower in a broad, flat powerband.

Obviously, the facts point to EFI as the logical American Iron induction solution, so Griggs Racing has gone the EEC IV route. The company has also done the displacement thing, using a stock 4.00-inch bore and a 3.250-inch stroker crank to arrive at 327 cubic inches. That's a nice compromise between working area and revability.

Plenty of compression is another definite attribute of the Griggs' AI engine, although exactly what the compression ratio is was not divulged. Bruce's only comment on compression is, "People wouldn't believe what we run in these things." We'd guess something near 13:1.

Big compression mandates small combustion chambers and pop-up piston domes, thus driving head and piston design. Griggs takes care of this by milling the heads and specifying a custom dome on its Ross pistons.

Of course, the camshaft, the intake, and the porting combination has to be torque-friendly. Griggs camming specs are secret, but they must be barely in the low-0.500-inch lift range, combined with short duration, as there just isn't that much power being made here. Word was that Griggs was playing with moving the lobe centers around, but then, racers are always moving everything around.

And speaking of playing around, at press time an induction experiment was being built from a hermaphrodite Trick Flow intake pairing (see the photos).

The good news is, there is only so much power of any kind that can be made with a 9.5:1 power-to-weight rule. Thus, stress builders such as high rpm and excessive heat aren't overpowering considerations, so the durability requirements are not excessive (this is somewhat offset by the brutal on-and-off duty cycle road-racing engines must endure). Aside from a strong Ford Racing Performance Parts R block-the stock 5.0 engine case won't last too many races before splitting through the number-two main bearing web-going wild on exotic materials or extra beefy parts isn't necessary.

Furthermore, exotic cylinder heads, zoomie exhaust, and all that aren't what make torque. That means more affordable, mainly streetable hardware is all that's required. This is especially helpful in the simple roller-rocker valvetrains, and well illustrated by Griggs' use of Air Flow Research 185 or Trick Flow Track Heat heads at most-not race stuff.

In fact, Bruce jokes that this is Griggs' "Summit engine" because it uses Summit gear for the heads, the valvetrain, and much of the rotating assembly. So, if not cheap, at least the basic engine bits are reasonably priced.