Thread: Clutch problem
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Old 07-12-2019, 12:57 PM
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Belgian1979vette Belgian1979vette is offline
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Join Date: Apr 2008
Location: Koersel/Belgium
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Just to update you guys :

I've ordered an adjustable throwout bearing from Novak ([Only registered and activated users can see links. ]) and did the math to see how long I needed to make the bearing. It still required several tries and taking the trans out in order to get close to a working setup.

On our cars you really need to get the clutch arm inside the trans as close to the trans as possible. Otherwise you will have it angled forward too much (towards the engine) and it will reduced your fork travel and effort and it will require you to put the bearing dangerously close to the clutch diafragm in order to get the clutch to release properly. This mostly will put the bearing in contact with the fingers and will make it fail in short order. This is what probably happened to mine.

There are basically 2 things that you can use to get the angle correct:
- the clutch pivot ball
- the lenght of the throwout bearing.

Both basically accomplish the same thing, but making the pivot ball longer, makes the arm touch the bellhousing (especially on my lakewood scattershield).
Lengtening the bearing is the correct way. I needed to lengthen mine to 1.650". The bearing that came with the clutch kit was the shortest possible, being 1.225". No wonder I had issues when just using it as is.

The difference lies in the so called 'clutch hat height' or the height of the diafragm fingers. This is not the same in all clutches. For example the Mcleod I'm using has far less of an angle.

When doing the math according to the Novak recommendations, you need to measure the hat height from the block rear face. (see website).

One other thing I found out is that no matter how well you set it up in terms of linkage and clutch fork angle, with the stock (as per workshop) recommendations on clutch free play, you'll only be able to get about .030 clutch plate total air gap. The Mcleod specifies .050" in their instructions, but you'll be only able to get there if you reduce your throwout bearing free play to something like .0100" which is too little in my opinion. With .030 air gap, the clutch frees up fine so far.

The problem on our cars is that the stroke of the fork is limited, so unless you start to modify the Z-bar nothing's going to change that.
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