Engine Buildup: 911 SC Carrera

Energized that I was now working on the "meat" of the motor, I eagerly removed the engine oil cooler from the front of the motor and then the cam oil lines and the chain housing covers at the rear of the motor, leaving the pressure-fed chain tensioners (introduced on the Carrera in 1984) chains and camshaft sprockets exposed. The Carrera-style pressure-fed tensioners are a popular update for all earlier 911s as they protect against disastrous chain tensioner failure better than earlier methods.

Horsepwer Per Displacement ComParison
Porsche 911 Street Engines (USA Spec)

The stock U.S. spec 3.2L's output of 68.6 hp/liter leaves plenty of room for improvement when compared to some of Porsche's best street engines.We're hoping to reach the 80 hp/liter mark with the planned modifications while still using 91-octane pump gas and remaining California-emissions compliant.

Source: "Porsche 911 Performance Handbook (2nd edition)" by Bruce Anderson

The upper and lower valve covers were removed, allowing me to see if there were any broken head studs. After unbolting the chain tensioners and removing the chain ramps, the chains can be lifted (but not removed until the case is later split) off the camshaft sprockets. Porsche tool P9191 is needed to hold the cam sprockets steady while removing the large bolts that retain the cams. Since these were on unbelievably tight, Steve held the tool on the three holes of each cam sprocket while I used all the leverage a breaker bar would provide to loosen the 19mm bolts.

The next step is one of the areas where close attention must be paid. When the rocker arms and shafts are removed from the cam towers, it is strongly suggested that each rocker arm and corresponding shaft be marked from where it came out of the motor.

Dwain, Steve and a host of others swear that reinstalling the rocker arms and shafts in their same location can help eliminate oil leaks. If the motor has high mileage and the rocker arms and shafts will be reconditioned or replaced, marking the orientation is not necessary. When the chain housings and rocker arms and shafts are removed, the camshafts should slide out of the cam tower assemblies with a minimum of fuss.

From this point, the motor can generally be stripped down in large chunks. I removed both cam tower assemblies, exposing the cylinder heads. The engine cooling tin that is located on each side of the cylinders must then be removed. Using a breaker bar and some elbow grease, I was able to loosen the cylinder-head stud nuts without incident and the cylinder heads simply slid right off the cylinders.

Unless you are just dying to know what the internals of your cylinder heads look like, there is no need to disassemble them. Most machine shops perform the disassembly as part of the service. If you are planning on reusing your pistons and cylinders, make sure you don't drop the cylinders while trying to separate them from the pistons. They are made from aluminum and are expensive to replace. The cylinders will usually separate from the pistons quite easily, but a few can be stubborn and may require a gentle tap with a rubber mallet.

Removing the pistons from the connecting rods requires a steady hand and safety glasses. A small flat-head screwdriver can be used to pry the circlip free that holds the wrist pin in place. The circlips have quite a bit of tension and if you don't grab onto them as they are being excavated they can-and will-fling to the other side of the room or worse, hit you square in the forehead. Once they are removed, the pistons can be separated from the connecting rods by using the handle end of a small screwdriver or a small punch against the wrist pin and tapping lightly with a rubber mallet. You don't have to completely remove the wrist pin, just tap it out far enough to release the piston from the rod. Remember to keep the pistons with their corresponding cylinders if planning on reusing them.

*Many of today's sport compacts and family sedans have much more horsepower than the legends of the past.

Almost there! I removed all ancillary pieces on the case exterior, including the ignition distributor, crank pulley, breather cover, oil thermostat and almost too numerous to count case fastening hardware. The case was then deemed ready to be split and after some coaxing with a rubber mallet the case separated and left me with a beautiful view of the crankshaft (with the rods still attached), oil pump and intermediate shaft assembly. The crankshaft will lift right out and the oil pump and intermediate shaft assembly only requires the removal of three nuts and then they come out as a unit. All of the internal parts will be disassembled to receive a thorough cleaning, be reconditioned and brought back to original tolerances, and then cleaned thoroughly again in preparation for reassembly.

Follow along with the build as the next installment will cover in greater depth the various options available to SC and Carrera owners during the course of a standard or high-performance rebuild. I will be relying heavily on the excellent products from industry leaders ARP, AASCO, Andial, Dansk, Extrude Hone, Mahle, Magnecore, Web-Cam and 911Chips along with the talents of Steve and Dwain to help build a powerful, dependable and emissions-friendly motor.