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Grady Clay Grady Clay is offline
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Join Date: Dec 2003
Location: Arapahoe County, Colorado, USA
Posts: 9,032

Don’t put it back together until we get this sorted out.

The linkage (particularly the arm) has a very limited range of effective motion before it hits something. I don’t see anything wrong moving the whole assembly one direction or another, it just must be compensated for with the location of the pivot and clearance to the transmission casting and pressure plate.

My normal advice is to retreat to absolutely stock everything. In your case, you have the skills to make this work better than original. The key is the angle of the arm. Using old, worn out parts you can manufacture an arm that works better than original. (Always make a spare.) I have seen some with a welded “dog-leg” to clear the pressure plate.

The two measurements you can provide are:

1) The distance between the center of the pivot and the center of the input shaft. You can screw a M8 bolt in the pivot insert and measure the distance, compensating for the diameters of the bolt and shaft.
The reason this is important is to be able to take a 914 casting and adapt it to the 225 mm clutch. Note the casting where the pivot seats.

2) The distance between the engine-to-transmission seating surface to the seat for the pivot. I have seen the pivot surface re-machined and fought the battle to get the linkage to work. This number is necessary when someone wants to convert to a 225 mm clutch and machines that surface.

Does anyone have a NOS side cover? It would be worthwhile to post the contour of the clutch cable ring on the side cover. It is not a straight through drilling; it has a specific contour that allows the clutch cable Bowden tube to change angles. Very important – actually critical for proper operation.

I think the type 911 was sort of a rush to fit the 225 mm clutch common to all 915s. It may be the casting design allowed too little remaining metal between the side cover stud drilling and the internal transmission and to the outside you picture. Given 30+ years, that wasn’t sufficient to prevent a corrosion problem.

I agree about the overflow vent. Most racers add a connection to an overflow tank required by rules. An additional advantage is you can use it to fill the transmission with lube.

Unless you are preparing a 911 for the Manhattan, grinding clearance for the arm is perfectly acceptable in my opinion. Yes, I prefer virgin stock OE but I compromise when improvements can be made.

Yup; It's always something! The art is making it right.

Old 10-11-2005, 07:38 PM
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