911's through 1989 have had a variety of auxilliary coolers, in addition to the engine-mounted cooler. The first auxilliary cooler was on the 1969 911S, and there were basically 3 variants after 1974: the loop cooler, the brass-tube cooler, and the radiator-type cooler. In most cases, for street driving these coolers work just fine. However, the demands placed on the engine while on the track can overtax the stock oil cooling capabilities.

Shortly after introducing CIS fuel injection in 1974/1975, Porsche changed how hot air was sent into the passenger cabin for heat and defrosting.  Starting with the first 911 in 1965, the original air system consisted of a duct on either side of the fan housing routing air through the engine tin to the heat exchangers. The new mid-70's system consisted of a fan mounted high on the left upper side of the engine bay, with 3 hoses, one for an air intake from the fan housing, and two hoses from the blower through the engine tin to each heat exchanger. Backdating the air system to the older style is easy to do, and Porsche sells the parts you'll need, or you can visit your favorite used parts dealer.

Bill Gregory, CVR

Well, here we go again. Bought a 1993 964 C2. Stock.  Just waiting for preparation for track usage, in addition to being a daily driver.  But before getting into upgrades, let's spend a little time on 964's. The prices have been recently getting into a more affordable range, particularly on the earlier 89-91 years.

By way of background, the 964's were introduced in 1989 in all wheel drive, or C4, configuration, whose drivetrain was evolved from the fabled 959 program in the mid-80's. Porsche said that around 85% of the parts in the C4 were new, with notable changes like a 3.6L engine, coil springs instead of torsion bars, ABS brakes, airbags, power steering, a retractable rear spoiler, and a new heating and air conditioning system that worked (!). Significant work was done on the body aerodynamics, and the 3.6L M64 engine was the first Porsche engine that was produced as a single engine for all worldwide markets, with 247hp. The manual transmission was an updated version of the G50 5 speed introduced in 1987. In 1990, the rear wheel drive version, C2, was added.  During the 964 program there were coupes, targa's, cabriolets, speedsters, and turbo looks, plus the limited run America Roadster, RS America (US only), and Carrera RS (non-US). models.  964's replaced 944's in the then 4 year old Porsche Cup racing series, and were used from 1990-1993.  45 964's were also prepared for a US race series that was cancelled, with the cars mostly being returned to street guise and sold.  In the US, upwards of 13,000 964's were sold.

At this point, the 964 line is pretty well shaken down, and there are some things to be aware of if you're considering buying one. Early engines were built without a cylinder head gasket, and in a small percentage of engines, can leak. Porsche fixed those that were found leaking at that time, with leaking being defined as wet to the touch. In 1991, Porsche updated the production engines by adding a cylinder head gasket, redesigning the cylinder head base, and installing all steel head studs. The 1990-on 964's use a dual mass flywheel, which helps isolate drivetrain vibration, however, the early Freudenberg units proved unreliable.  In 1992 Porsche changed to LUK-manufactured units, which have stood the test of time. In late 1993, Porsche added a vent kit for the distributor, to help prevent the dual distributor rubber belt from breaking due to ozone concentrations. There is a $10 kit to add this to earlier 964's. 1989-1991 964's need different spacers on the steering rack if you want to fit 17" wheels. The rear suspension geometry was changed in 1991, which is important to know if you make any rear suspension upgrades. At around 50,000 miles you should replace the dual distributor drive belt. As a Digital Motor Electronics (DME)-based Porsche engine, you should consider carrying a spare DME relay (993.615.227.00, around $22) in your glovebox.

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Some people aren't keen on the 964 C4 all wheel drive system (as compared to the different and improved system of the 993, for example), so be sure you're OK with it before buying one. C4's have a high pressure (up to 180 bar or 2,600 psi) non-vacuum, hydraulic-based brake system, as opposed to the more conventional system with vacuum assist. This is important if you bleed your own brakes, as it's difficult, if not impossible, to properly bleed the 964 C4 brakes without a Bosch 9288 system tester, aka "hammer", or, it's replacement, the KTS-500. These tools run $3,000-$6,000, and Bosch no longer supports the "hammer".  C2's and RS America's use a vacuum-assisted brake system and can be bled at home (2 bar or 30 psi on your pressure bleeder). If your interests involve the track, the RWD 964's may be the better choice  Of course, have a pre-purchase inspection done, so you know what you're getting and that you negotiate the best price for it's condition.

So what's it like to drive a stock 964? It's more quiet and isolated from the road and environment than earlier 911's.  The 3.6L engine, with it's additional horsepower,  is a joy.  It's heavy at around 3030 (C2) to 3250 (C4) lbs, the suspension is basically what you'd expect, although it plows, or understeers. The heating and a/c system really does work better than earlier 911's.

So, with this background on the 964 line, next month we'll look at modifications to enhance  safety and performance at the track. If there are any questions, I can be reached at sansho@rennlist.com.