With fuel pressure set at 38 psi and TPS voltage set at 0.96 volt, we made our first dyno pull. Peak horsepower came in at 244 and torque twisted up to 290 lb-ft. We noticed there was a slight misfire; a replacement coil cleared up the issue and provided 247 hp and 293 lb-ft of torque at the wheels. Keep in mind, we were running the car on its 87-octane diet. For the next pull, we switched to premium 93-octane fuel and added two more degrees of timing for 14 total at base. Power rose to 249 hp and torque stayed the same at 293.
About this time, we realized that the coolant system was being pressurized, and surmised that we had a damaged head gasket. While the air/fuel ratio looked great on the dyno, and no detonation was detected, we did have some problems with what we thought was air in the cooling system. The usual procedure when refilling a cooling system is to fill it and let it come up to operating temperature so the thermostat opens. Then you can fill the remainder of the system.
Modular cars are far more susceptible to air bubbles in the system, and we thought we had ours taken care of, but the first long drive had us mildly concerned about the temp reading. A subsequent refill and about 20 minutes of idling said everything was OK, but the load that the road and dyno puts on the engine is what made the gasket vent to the cooling system. After contemplating the issue, we came to the conclusion that your author had not properly torqued down the ARP head studs. He had followed the factory torque specs at 72 ft-lb on all bolts. ARP expects you to torque the short studs to 75 ft-lb and the long studs to 85 ft-lb. The long studs run along the top, and that's exactly where the gasket failed.
In the end, we spent over $3,700 on this rebuild, but we did use some items and replaced a few others that you might not need. Without those pieces, the build price tumbles to a hair over $2,400-very doable in this day and age. Horsepower and torque are respectable and should make this Pony gallop a little faster. Whether or not the 2 hp is worth 20 cents extra per gallon is up to you. Given the long commute our project car has each day, the horsepower isn't worth the extra money. That may change, however, as we're looking to install a budget-conscious, intercooled turbo system.