GT6 MkI clutch - very early engine

[Joachim Moeller]

Hi all, while restoring my 1967 GT6 MkI I've had the engine running for the first time last week. The clutch release bearing was fouling the clutch springs (clutch not engaged - terrible noise) so I've removed the engine again. While adressing myself to the bearing I've found that everybody is selling part no. GRB209 as the bearing to use BUT Rimmers say that you can't use it for the very early GT6 MkI engines that I've got. Is this true? What's the alternative (no according to the Rimmers website)? I have three early MkI engines in all and all clutch release bearings look the same as GRB209. Thank you for any help. Cheers Joachim

[Pete Lewis]

not sure why this is , but only thing i have identified across the range is many replacement bearings are 15mm thick where the orig was 19mm thick this 

reduces the angle of the lever and upsets the ratio 

there was a load about this on the lost forum ,  the orig was an RHP number , still available from some suppliers of bearing 

just refitted a new shed and have no idea where to find the part to retrieve the correct part number  hey ho  whos out there ??

 

Pete

[Joachim Moeller]

Thanks Pete,

is the bearing in constant contact with the diaphragm springs (constant turning)? Or is it making contact only when the clutch is depressed?

 

Joachim

[Dick Twitchen]

Joachim, 

I used GRB209 when restoring my '67 Mk1 and have had no issues, although sourced from Canley Classics following frustrations elsewhere.  Same Part Nos is shown for Vitesse with the same engine. I would be tempted to buy from someone who actually uses the parts on their own work even if having to pay a premium; Jigsaw does it for me.

Dick

[Joachim Moeller]

Thanks Dick,

I have replaced the bearing (with GRB209) and will see what's happening when it's all back together again. What have you used for greasing the carrier/fork? The workshop manual says zinc oxyde grease and I can't find that here in Germany (so far).

 

Joachim

[Pete Lewis]

if  GRB209 is only 15mm thick you need to extend the sperical post a little to get the lever in its central see saw position or the leverage becomes 'late' and the pins which press the carrier become below the centre line of the tube and this will pitch th carrier and cause judder in the future .

 

I have fitted washers under the sperical post to gain height which seems a compromise if needed

 

if the tcarrier has worn where the pins load  you can remove the anti spin pin and relocate it in an un worn sector.

likewise the throwout pins can be replaced by welding in cut down clevis pins. to make them round again.

 

just some thoughts 

 

Pete 

[Joachim Moeller]

Pete,

adding a washer under the post to gain height means the bearing should be in permanent contact with the springs? This would mean the bearing itself is turning even if the clutch pedal isn't depressed. (This would explain the noise I've got with the old bearing by making contact with the springs from time to time)

[Pete Lewis]

all small chassis and others have a static throwout so its supposed to be in contact all the time the load appied is from the spring in the slave cylinder, its its noisy its down to lack of load and the noise is skidding , and a light touch to the pedal and it stops then its this making the noise.

 

all down to brg drag and poor  diaphragm finger finish.

    this then wears a groove in the brg. and pedal loads increase as the fingers have to climb out of the formed wear groove. 

 

adding some small  packing under the pedestal to compensat for the thin bearing just moves the lever to a 50/50 position and not a 75/25 ratio for when the lever is well past its home position there is  increases pedal  loads .

 

             Pete

[Joachim Moeller]

Pete,

 

first of all thank you for all the information. Your help is most appreciated. As I don't want to go the trial-and-error-route more than necessary I have a few more questions. Regarding the post, is it as simple as basic mathematics - say, the bearing is 4mm less in height so I put 4mm washers under the post to gain height? What about the lever geometry? Adjusting the slave cylinder accordingly (4mm)? What grease do you use for the throwout pins?

 

Cheers

Joachim

[Pete Lewis]

as the pivot is aprox half way from each end you dont need 4mm 

 

we used one or two simple washers to get the lever 'midships' in its operational angle of  travel. 

 

if you added 4 mm the post would probably rock out of its bore, its only as deep as the hsg casting.

 

no grease on the pins that attracts dust and grinds things away even more

 

many use a grease on the 'tube ' but again this clogs up with dust .

  more modern ventures use a plated and dry assembly in here.

 WSM states use a vinc oxide grease sparingly to the pivots and sleeve.

 I guess any hi  melt  temperature grease would be OK  used sparingly

 

     there's no easy compromise , the design is old hat,  the anti spin pin is added to stop the carrier rotating and wearing grooves in the front cover tube

     but then wear is confined to two small contacts and these end up with a dimple 

     if its left to spin the fork pins wear even more 

         what we all  need is someone to make a 3D printed concentric assy to fit the front of the gearbox....Hmmm   !!

  

just some ramblings 

    Pete