Found the problem!

From Zero 250611

So new bigger master cylinder in (can see in the photo how much bigger the new one is), while the engine was out we checked carefully that we were getting full travel on the slave cylinder. I pushed slowly on the pedal while Mike held the thrust bearing pushed back as far as it would go. The full 1 inch of travel was achieved with the pedal on its highest ratio (there's three holes drilled to allow us to vary the pedal ratio). We thought we'd need to get more extension against the clutch cover to spaced out the cylinder with a few washers. Engine back in, still no luck disengaging clutch. Pushed pedal again and 'POP', fluid all over the floor... No option for it but to get engine out. How depressing.

With the engine out it seemed the slave had only slightly over-extended and pushed fluid out as the slave cylinder had gone back into the slave housing. Then after a bit of searching on Locost Builders I thought I'd take another look at the clutch plate. It had witness marks around the outside of the splined bit, it seems the fixed guide tube in the slave was permanently holding the friction disc hard against the flywheel. Some measurements taken, and without the washers we just added, there was only 0.3mm clearance between guide tube and cluth plate...

So, the spacer we had made is too thick. Looking at the clutch cover plate, the pressure ring can only come out 4mm, so we thought we'd skim 4.5mm off the spacer to give a bit of clearance. Just trying to track down a local lathe person today then hopefull we'll be back in business.

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This is the guide tube.

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Pink arrow shows the marks from the end of the guide tube
Green arrows show depth of plate from finger. Engine face to fingers = 60mm, fingers to plate = 19.3, so engine face to plate = 60-19.3= 40.7

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Blue arrows show guide tube to mounting face. With the slave spacer in, depth = 41mm
This gives just 0.3mm clearance.

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So clearance needed to allow plate to move away from flywheel, max movement would appear to be 4mm (yellow arrows).

More bad times..

Disaster after disaster. We realised that due to the Omega originally running a Dual Mass flywheel which is very thick, and we are using the saab one which is thin, we'd need a spacer behind the clutch slave to make up the distance. Using our previous measurements where we thought all would be fine, we realised that when clutch and gearbox are mated the thrust bearing is pushed back against the spring around the clutch slave (this should make sense if you're looking at it). The thrust bearing is always pre-loaded against the clutch fingers.

Measuring it extended and fully depressed came to 25mm ish, so we had a spacer bought from SBDEV, part ref CLT-HCS-30, lathed down to 24mm.

Fitting it all back together, we bled it through to get what felt like a firm pedal. However depressing the pedal the full travel of the 3/4" bore Land Rover Clutch Master didn'r release the wheels from the engine. Some head scratching and it seems we just aren't shifting enough fluid to fully extend the the slave. So we found a single port 1" dia brake reservoir for a Series 3 Land Rover on ebay and ordered that plus a reservoir. Waiting for delivery to see if we can finally get a break with this build!