clutch question - a 69 clutch in the 67 normal?

[tadink]

Hey guys....

one of the posters over on early911sregistry has suggested using 69 clutch parts when I replace the clutch on the 67 normal. I have not heard or read about this suggestion before...maybe one of the SWB guys can weigh in on this?

IF it is a good idea....can someone suggest a shopping list on what to buy? Has anyone else done this?

many thanks in advance....

tom

[Grady Clay]

The clutch parts for the ’69 911T and ’69 911E were basically the same as all the SWB cars. These were 215 mm push-type clutches. The difference came with the ’69 911S only clutch parts. These were ‘lightweight’ push-type 215 mm clutch parts.

There were two 911S pressure plates: One steel with a thick copper covered (plated?) friction surface. The soft copper didn’t work well as it easily scored. There was a steel housing with an aluminum moving plate that was very good. It had a ‘flame sprayed’ steel facing on the aluminum plate. There was also a period 906 pressure plate with lightening holes in the steel housing.

The clutch discs were all basically the same except for a thinner, 911S only disc that was only used with a different depth steel/aluminum pressure plate. You will find discs with both 4-spring and 6-spring for the splined hubs. I don’t see any significant difference between the two. All discs have the spring system between the two friction surfaces.

There was only one cast steel flywheel that had six flywheel bolts. These are ‘use once’ expensive bolts. That said, there was a very early 901 flywheel with a different (‘6-volt’) ring gear tooth pitch. The similar 215 mm flywheel for the 914-6 has ignition timing marks on the flywheel. There is an interchangable 215 mm forged steel flywheel for the 906 that is very light.

The flywheel bolts, clutch cover bolts, pilot bearing and clutch release (TO) bearing are all the same although there was an update (interchangeable) with the ’67 TO bearing. The later part requires two plastic pieces alongside the TO bearing ‘ears’.


All that notwithstanding, I don’t think the ’69 911S clutch parts are available. I don’t know what the various parts that are commercially available are like. Perhaps someone can post the current choices. Sachs part numbers are helpful.

There are many race-only clutch parts. Typically the discs don’t have the spring system between the two friction surfaces. Some have individual ‘puck-type friction pads. These are not suitable on the street. They don’t slip well and are terribly ‘juddery’. They are ‘off-on’ clutches.

There are also racing multi-disc clutches. These too (almost like the CGT) are poor on the street.

Overall, a very lightweight clutch/flywheel assembly is great for racing. Conversely, a heavy (large rotational inertia) clutch feels very good in traffic. Each is poor at the other job.

The clutch is a ‘designed to wear’ set of parts. In the overall scheme of things, it isn’t too expensive. I tend to normally drive in a ‘conserve the clutch’ mode. This is where I minimize the length of time that the clutch is slipping and minimize the amount of torque transmitted while slipping and all at the lowest practical rpm. There are then circumstances where I can severely abuse the clutch. Typically those are the few ‘jack-rabbit’ starts I succumb to and a technique of using the clutch ‘trail-braking’ into a turn at the limit of traction.

Aah, engineering compromise.

Best,
Grady

BTW, If I have not recalled anything correctly or mis-stated something, please feel free to offer corrections. Less than perfect memory these days.
G.

[tadink]

Thank you very much - Grady - for your thoughts.

So, what is your recomendation on this issue? Should I try to find a 69 clutch set up or just stick with the stock 67 set up?

cheers!

tom

[tadink]

Hey Grady - or anyone...do I need this?

225mm pressure plate

FS - 225mm Sport Al Pressure Plate

[Zeke]

Originally Posted by tadink

Hey Grady - or anyone...do I need this?

225mm pressure plate

FS - 225mm Sport Al Pressure Plate

No, because as Grady stated, you have a 215 MM ass'y.

BTW, of all Grady's posts, that one was particularly good. I say that because I went searching for info on this and came up empty. So, take heed to what Grady Clay is offering.

[304065]

These days you pretty much buy the Sachs kit from Pelican and call it a day. The "S" parts are not only different, they are three times the price. . . and as our resident Final Authority on all things Porsche (Hey there Grady!) expertly stated, clutches are either street or race, and none of this in-between lightweight bronze flame coating jazz. Hell, even if I owned a 67S I would probably run the normal clutch and keep the S part on the shelf.