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No Need to Use Avgas or Race Gas in Your 356

September 27, 2010 | Troubleshooting & Repair | 0 Comments
  By David Jones Pump gas is more than adequate for our cars and 93 octane at the pump is around about what we used to buy as 100 octane back in "the day". It just don't have lead in it which is a good thing. Unfortunately it may have ethanol in it which is a bad thing. Race gas and aviation gas is  made from the same base stock which is known as an alkylate. Only refineries with what we call an alkylation plant can make it so it is somewhat specialized. The refinery I work in does not have one so we only make "motor gasoline" Avgas is made to very specific formula which must be tightly controlled to prevent airplanes from falling out of the sky. It has a low RVP to prevent it gassing off at altitude and little to no distillates so it does not oxidize quickly like 87 octane motor gasoline. This is required because it can often sit for relatively long periods of time in parked aircraft in large quantities and if you know an airplane owner he will tell you if you ask h...

Fuel Valve / Fuel Cock FAQ

September 27, 2010 | Troubleshooting & Repair | 0 Comments
Text and photos by Barry Lee Brisco   The fuel valve or fuel cock (also called a "petcock", shown at right in a 356A) is one of those 356 peculiarities that generates frequent questions from new owners. Not used to having a car that offers control over fuel flow from the driver's seat, they are often either baffled by it, ignore it, or may even decide to remove it! In fact, it is a useful device that serves multiple purposes, and it is worthwhile to take a moment and understand its function. While at first glance it may appear to be dangerously exposed, Bruce Baker notes that after 40 years of seeing a few hundred 356s get mangled in accidents, he cannot remember a single incident of a fuel-related fire or a leaking gas tank (read more about 356 fuel system safety issues). Q. Which position is "on" and which is "off"? Q. What do all those funny German names mean? Q. How do I use the "reserve" setting, and how much fuel is in "reserve"? Q. Why not just leave the fu...

Gas Smell Troubleshooting

September 27, 2010 | Troubleshooting & Repair | 0 Comments
By Geoff Fleming and Tony Ryan Where to look when you smell gas inside the car Geoff Fleming: You will have to do a once-over check of various areas. Start at the engine bay, since a gas leak there can result in catastrophe. Check carb floats and look for worn hoses ( especially the link behind the fan shroud that joins the metal lines.) and at the fuel pump. Another culprit, lurking just out of sight, is the rubber line from the body to the engine bay. It should be replaced every five or so years, as it becomes porous and causes fuel smells. Next, I would examine the fuel cock. These are outboard on the T-6 series, (1962-1965). You might have developed a slight leak at the sealing surfaces. Check the hose connections too. If really ambitious, or if the obvious suspects prove innocent, remove the tunnel covering and check that the flexible hose "elbow" on the fuel line hasn't given up the ghost. Likewise, a fuel tank can develop leaks along the seams. Maybe you...

Hand Throttle FAQ

September 26, 2010 | Troubleshooting & Repair | 2 Comments
Contributed by Various 356Talk Contributors   Hand throttle location in A coupes and cabs Arrow shows hand throttle location in T5 and T6 B coupes and cabs Arrow shows hand throttle location to the right of the ignition, in Speedsters, Ds, and T5 B Roadsters Arrow shows hand throttle location in T6 B "twin grill" Roadsters (photo courtesy of T6 Roadster owner Tom Farnam) View behind dash of A coupe showing hand throttle cable housing The 356 hand throttle was introduced with the A model in 1956, replacing the choke used in the pre-A cars. In coupes and cabriolets it is located between the tach and speedometer, while on Speedsters, Convertible Ds and Roadsters it is to the right of the ignition switch (which is to the right of the steeering wheel, opposite coupes and cabriolets). By modern standards, the hand throttle is an anachronism, and there are regular questions on 356Talk regarding it's origin and use. Here are answers to these questions: Q. Can ...

A Systematic Approach to Full Throttle

September 26, 2010 | Troubleshooting & Repair | 0 Comments
By Ab Tiedemann The ball sockets should be checked for wear before the task is started and all replaced if any clearance or binding is felt. There are 9-10 sockets to consider and .05-.1 mm clearance in all those places could amount to about 12-15 mm of arc at the accelerator pedal. They also need some lubrication. Graphite grease works well. There is a fundamental design dimension that should serve as the starting point and it should be preserved when you are finished. The center of the ball on the little bell crank that attaches to the fan housing and connects to the pull rod coming up from the bell crank at the transmission should be 50 mm from the vertical surface of the fan housing. This is the starting point. The geometry is illustrated in the 356 C Workshop Manual, p SF 26, Figure 8. With the pull rod free from the transmission bell crank and the push rods free of the carburetor connection, adjust the near vertical push rod that connects the aforemention...

Velocity Stacks — For Looks, For Power, or Both?

September 26, 2010 | Troubleshooting & Repair | 0 Comments
By John Wilhoit We tested 6" vs. 2.25" velocity stacks mounted to Weber 44IDF carbs on one of our 1925cc single plug engines. There was a change in the torque curve and (interestingly) no significant change in the fuel curve. There was an improvement of about 3 ftlbs in peak torque but a loss in the upper range. I determined the improvement to be insignificant when considering the weird look of such a tall air cleaner. Incidently, we've tested with and without air cleaners and have consistently seen no improvement by eliminating the K&N air cleaners; on the other hand, the Porsche factory mesh cleaners do have more restriction compared to the K&N, so eliminating them or switching to K&Ns will bring an improvement in horsepower. Using a filtering screen over the top of velocity stacks instead of an air cleaner will seriously affect the flow and should be avoided. (Click here to view a larger image of the curves shown below) Reprinted by permission of Wil...

Developing the Flow in Zenith Carburetors

September 26, 2010 | Troubleshooting & Repair | 4 Comments
Text and photos by Gary Koehler [Editor] As Gary points out, while significant flow rate gains were achieved as the result of the extensive modifications he made to the Zenith 32NDIX carburetor, he has not yet done dyno testing of an engine with his modified carburetors and compared the results to the same engine with stock carburetors, so potential HP increases have not been measured. Also, he carefully notes that "Flow rate gains do not guarantee HP gains unless all other elements in the system are designed accordingly." I have finished the rebuild and modify phase of the Zenith carburetors for my big bore rebuild, realized some nice flow and velocity gains, and wanted to share what I did with Registry members who are interested. While I don't claim to be a carburetor expert, and with due respect to those who have done carburetor, flow bench and dyno testing, I could find no published flow data or guidance for modified Zeniths, so I decided to flow test the modifica...

Transmission Oil

September 26, 2010 | Troubleshooting & Repair | 0 Comments
 By Pat Tobin, John Jenkins, Harry Pellow. Question by Joe Babin   Q: After reading thru the tech page on gear oils at Redline's website, I'm trying to decide which one of their products to use. My transaxle is original with 115,000 miles on it. No problems, no leaks, shifts well and I want to keep it that way for as long as possible. Any suggestions? Other manufacturers that have superior gear oil? A: It is questionable whether any synthetic gear oil is best for manual transmissions--it may be too slick to allow the synchros to get a grip. There have been conflicting reports about this on the [356Talk] list - some say that a synthetic (not necessarily Red Line) works fine, others say no. In some of Red Line's lit I once saw a mention of some sort of friction modifier intended to allow use in manual transmissions. But the last time I read the bottle of Red Line gear oil, right on the bottle there was a caution ab...

Porsche 356 Transaxle Upgrades

September 26, 2010 | Troubleshooting & Repair | 2 Comments
Tunnel Case (Types 644,716,741) By Mike Robbins The factory did not always make revisions at the serial number specified in technical literature. Some of these upgrades are very beneficial; others are of lesser importance. The following table is a work in progress. If you have comments and/or additions, please email Barry Lee Brisco, Website Technical Editor, at barry.brisco@356registry.com . Abbreviations used: SB = Service Bulletin; SMS = Shop Manual Supplement; PC = Parts Catalog.   Beginning Serial # Up To Serial # Upgrade Documentation 11001 14053 Change from steel to bronze shift forks SB 14/57 11001 ? (644) Add cups for front mounts. Revise quantity and positioning of reinforcing plates. SB ? 11001 15960 Revised operating sleeve: lead angle changed. SB 31/57 11001 16744 Change intermediate plate & clamp plate: 4 bolt to 5 bolt. SB 27/57 11001 22425 Change to flanged axle nuts. - 11001 22996 Chang...

Clutch Alignment

September 26, 2010 | Troubleshooting & Repair | 0 Comments
Text and photo by Ab Tiedemann I have taken the clutch alignment task one step beyond the shortened input main shaft tool that some use. Below is a picture of my set-up which shows the extra two aids used to center a Kennedy pressure plate and the main shaft for the disc when installing the clutch cover on a 200 mm assembly. The "extra aids" are fashioned similar to the 911 tool, but have the interface for the 356. These aids are in production. Look for an announcement on 356Talk when they are ready. There is no "Factory tool" listed for this procedure. It is one of common sense or at least one that has logic for the mechanically apt. When the 911 was introduced, the clutch plate was initially centered with removable loose pins [referred to in the 911 Worshop Manual as "dowels"]. See illustration III.245 of Section 52E in the 911 Workshop Manual. [Click here for a PDF scan of that page in the manual] The Factory tool number for this task sequence is unknown to m...