Clutch fork position

Technical advice Q&A

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valerea
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#1 Clutch fork position

Post by valerea » Thu Apr 15, 2021 11:50 am

Hi
I am concerned about the position of the fork as it exits the bellhousing.

There seems to be little travel distance and is it enough to depress the cover diaphragm?

This is a full new clutch. I contacted the company who said it was for the 4.2 Etype (jan67)

What worries me is the one removed was the thicker cover. The bell housing is the correct 4.2.

Anyone had the same issue, or will it depresss the splines enough?

Thanks in anticipation

Paul
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mgcjag
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#2 Re: Clutch fork position

Post by mgcjag » Thu Apr 15, 2021 12:01 pm

Hi..Paul.....what about the release bearing......what one have you used. ...did you buy a clutch kit complete...usually you what the fork roughly in the center.....if you havent installed yet then worth removeing gearbox and checking on the parts youve used....also what flywheel.....original or a skimed one.....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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valerea
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#3 Re: Clutch fork position

Post by valerea » Thu Apr 15, 2021 12:48 pm

Thanks for your reply.
The flywheel was original but lightly skimmed by engine rebuilder who didn’t comment about its ‘thickness’

As I said I was concerned at the difference in thickness with the cover I took off

Yes full clutch kit

Would it be enough do you think?

Thanks again

Paul

Here is a photo of both covers
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mgcjag
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#4 Re: Clutch fork position

Post by mgcjag » Thu Apr 15, 2021 4:56 pm

I think your problem is more likely to be the thrust bearing.....the fork dosnt need to move much but i would like to see it more in the center of the opening.....thats why i sugested opening it up and and looking at the release bearing....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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politeperson
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#5 Re: Clutch fork position

Post by politeperson » Thu Apr 15, 2021 6:19 pm

Steve,

I have seen this on 2 E types now with new 3 piece clutch kits.

When fitted, the arm is too close to the end of the bell housing slot.

Didn't you think there were two different bearing heights ie from the pivot point to the thrust face?

I could see that if the wrong one was fitted that would cause this issue.

I did question SNG the other day and they couldn't find any alternatives in terms of different part numbers.

Its a bit worrying.

I have one car in the garage at the moment with a new clutch and an original thickness flywheel. When you push the clutch hard the clutch arm smacks the body of the car because it is so far back.

Definitely worth investigating.
Its true, but Enzo never said it
Too many E types
XK120 SUs

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#6 Re: Clutch fork position

Post by mgcjag » Thu Apr 15, 2021 6:39 pm

There are a few different height release bearings...all look very similar untill you put them side by side...this photo shows just two....worn out carbon on one but what were looking for is difference from the pivot point
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And someone elses photo
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Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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#7 Re: Clutch fork position

Post by valerea » Thu Apr 15, 2021 6:51 pm

hi

I think I will have to split it again. I bought the clutch set from SNG and was assured by them and manufacturers direct it was the correct set.

I did ask onJag loverssite and kindly had this interesting response

inlinesix inlinesix Terry Sturgeon
April 15
Typically on clutches this size the release bearing needs to move .375" in, once contact with the center of the diaphragm occurs, to release the disc. Given the mechanical advantage of the lever based upon it’s lengths each side of the pivot (1.6 to 1) the outer end of the arm needs to move .600 inches more or less to release the disc.

it will just about clear the 1/2 inch but as the thrust bearing wears it will not give much adjusting

I am really not sure how to progress even if the thrust bearing is a different size! the suppliers seem unaware of this problem!

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#8 Re: Clutch fork position

Post by steve3.8 » Thu Apr 15, 2021 6:53 pm

The clutch pad heights could be the same when bolted down? , your old cover looks like an original Laycock item . The latest Borg + Beck kits now have a similar look to the Laycock.
Image

With the amount of work involved it's good practice to prove the clutch operation before you refit the engine into the car .
it was hastily/ roughly engineered but i made a remote test master cylinder about 20 years ago -- just a cheap cylinder with a screw in reservoir-- also useful for caliper piston removal.
Image

Connect it up to the slave cylinder- with a gear selected you will be able feel the biting point when turning the propshaft flange by hand.
The clutch arm position is to the left on mine with the new clutch just fitted--it operates ok'

Cheers
Steve
Steve3.8

64 3.8 fhc, 67 4.2 fhc

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valerea
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#9 Re: Clutch fork position

Post by valerea » Thu Apr 15, 2021 7:00 pm

thanks Steve. maybe I will try a mock up before I split it but Im nit hopeful

you are correct the PP I took out was a Laycock alas now long gone!

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#10 Re: Clutch fork position

Post by PeterCrespin » Fri Apr 16, 2021 7:31 pm

Did you not try my suggestion on Jag-lovers?
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 2001 Vanden Plas

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MarekH
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#11 Re: Clutch fork position

Post by MarekH » Sat Apr 17, 2021 7:21 am

Dear Paul,

if you look at the clutch fork, for a 6 cylinder car, you'll note that the pivot point on the bellhousing is nowhere near the centre of the fork, so the amount of horizontal movement at the slave cylinder pushrod end is multiplied up by this ratio when moving the thrust bearing off of the pressure plate.

kind regards
Marek

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mgcjag
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#12 Re: Clutch fork position

Post by mgcjag » Sat Apr 17, 2021 8:04 am

Lots of useful information already on the forum here http://forum.etypeuk.com/viewtopic.php?t=16018
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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#13 Re: Clutch fork position

Post by abowie » Sat Apr 17, 2021 8:47 am

PeterCrespin wrote:
Fri Apr 16, 2021 7:31 pm
Did you not try my suggestion on Jag-lovers?
Said the actress to the bishop...
Andrew.
881824, 1E21538. 889457. 1961 4.3l Mk2. 1975 XJS. 1962 MGB
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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