There are still a gazillion air-cooled 911s on the road. A problem that has forever plagued the ’76-‘87 911s is the cylinder head studs. A brief refresher: Since the start of production of the 911 in 1964 and through 1967, Porsche used a sand-cast engine case. The sand casting method is very expensive since a foundry tech has to make a mold for every engine. Also the cases are heavy because of the amount of aluminum used. Around 1965, Volkswagen started using the pressure-cast method of producing engine cases. The molds are reusable with the pressure cast method. Manufacturers are always looking for ways of reducing cost. So in 1968, VW engineers started using a magnesium/aluminum alloy for the cases. They could use less material since the magnesium would strengthen the alloy. This probably worked great in the frigid climes of Europe, but not so much here in the American southwest. The cases were so rigid that the pressure on the case exerted by the cylinder head studs (caused by ever-increasing engine temps to meet emission standards) would result in the threads in the holes for the studs breaking. The result was loose cylinder heads, compression loss, and severely diminished power. In 1968, Porsche adopted the magnesium alloy pressure cast method for case production. This worked great in the 2.0 L-2.4 L engines. In 1974, Porsche bumped the displacement to 2.7 liters. Engines were running hotter to meet emissions (in 1975 they incorporated a five-blade cooling fan to increase the engine temp). I was a unit tech (engine and transmission repair) at 30 November (Maniacal) Mechanical Musings: Make it Stop! By Ed Mullenix then Forest Lane Porsche+Audi. I’ll bet I put thread repair inserts in 50 engines when I worked there. Porsche liked their alloy pressure cast cases, so their fix was to change the exhaust-side stud material from steel to “dilvar.” Dilvar had the expansion coefficient of aluminum; the theory was that the aluminum cylinders were expanding more on the lower (exhaust) side, causing the threads in the case to fail. Unfortunately the dilvar alloy was so brittle, the studs would break; so much for the bestlaid plans of mice and engineers. The alloy was extremely hard; carbide drill bits were required to drill out a broken stud. In 1976, with the introduction of the 911 Turbo, Porsche used aluminum as the case material. It was more forgiving than the magnesium alloy. They kept the aluminum cases through the SC, 3.2 Carrera, 964 3.6, and the 993. Several iterations of head stud were tried. The problem does not show up on the 964 or 993 cars but is a ticking time bomb on the SC and 3.2 cars. If you are thinking about the purchase of a 3.0 or 3.2 911, absolutely have a pre-purchase inspection done. Include removal of the lower valve covers (drain the oil out of the engine, to be refilled later), with a torque wrench set at 12 ft-lbs (half the prescribed head nut torque of 24 ft-lb), turn the wrench, and observe if there is any movement of the head nut. If there is any movement at all, that stud is in an early stage of failure. I have removed lower covers during the course of an engine maintenance and had sections of broken head stud with nut still attached fall out on the floor. Replacing head studs is essentially doing a “top end” on the engine. Depending on where the stud broke, it could mean total disassembly - see attached pic of an SC case with studs broken off inside the case. I no longer use dilvar studs; I use steel studs for upper (intake side) and lower (exhaust side). In 20 years, have not had a single problem using steel studs. Having fun!!
R E I M A G I N E D 1321 COMMERCE STREET | 214.651.3615 | THEFRENCHROOM.COM You can test your knowledge (or Google search ability) of all things Porsche by participating in the monthly trivia contest posted online at http:// mav.pca.org/trivia. Answers are due by the last day of each month. The winner of the trivia contest receives a $25 gift certificate from our sponsor, Zims Autotechnik. In the case of ties, a random drawing determines the winner. Here are the questions for the September 2019 Trivia. We went with a trivia that brings Q&A this month dealing with miscellaneous Porsche items. The winner this month was Tom Martin, getting all 5 of 5 correct. Congrats to Tom. 1. A company in England builds very high-end model car kits. This company has a 1/8 scale model of a 1957 Porsche 356A. The headlights work, the doors open by remote control, and more. You too can have one for about _________! a. $3500 b. $5800 c. $9200 d. $11,300 Source: https://tinyurl.com/y3kyd5fc Maverick Trivia: Are you a Porschephile? Jerry DeFeo sponsored by Zims Autotechnik Answers: 1)d, 2)c, 3)b, 4)b, 5)b 2. Anton Piech and Louise (Porsche) Piech were the parents of Ferdinand Piech, “father” of the 917. Carlo Abarth was an Italian motorcycle racer in the 1930s and founder of the Abarth company. Abarth married someone very close to Anton Piech - who was it? a. Piech’s sister b. Piech’s sister-in-law c. Piech’s secretary d. Piech’s mistress (Abarth was Italian you know) Source: Excellence magazine, April 2012, p 48 3. Carlo Abarth was responsible for the arrangement with Porsche to build the Type 360 1.5-liter Cisitalia Grand Prix car. Porsche was under contract to build three more items for Cisitalia: a small tractor (Type 323), a sports car (Type 370), and a _________ (Type 385). What was a Type 385? a. Turbine Indy 500 car b. Water Turbine car c. Electric all wheel drive car d. Turbocharged Diesel sports car Source: Excellence magazine, April 2012, p 48 4. Recently at a Monterey auction, a 1939 Porsche Type 64 failed to sell due to a bidding error. It mistakenly had an opening bid of ________ ? a. $10,000,000 b. $30,000,000 c. $50,000,000 d. $70,000,000 Source: https://tinyurl.com/y48savpf 5. The first Porsche 911s had some interesting items that you may not see the newer models. Which of the following four items did the 1965 Porsche 911 NOT have? a. Wood dash b.Weber carburetors c. Gauges with green numbers d. Orange vs red Porsche crest on the front deck lid Source: Excellence magazine, June 2012, p 80 31