Clutch release mismatched component?

ngtcj · Post by **ngtcj** » Sun Apr 20, 2014 5:07 pm

I have an ex-SD1 block and bell-housing mated to an R380 box but even with the slave piston fully extended my clutch release mechanism doesn't push in the clutch fingers, so I think I must have a mismatched component. As far as I can tell the components are individually correct so I'm flummoxed.

From the following measurements and/or linked photos can anyone point out what is wrong?

Depth of bell-housing = 179mm.

Distance from face of engine block to face of flywheel = 20.3mm.

Distance from face of flywheel to release bearing contact point on clutch fingers = 43.4mm (with new 9mm clutch plate fitted and cover bolted up).
Depth of clutch cover = 46.65mm

Height of pivot post (excluding threaded stud) = 44mm.
Distance from face of engine block to tip of pivot post = 117mm.

Distance from face of release bearing to centreline of slipper posts = 56mm.

Distance from pivot point on release arm to centreline of slipper posts = 80mm.
Distance from pivot point on release arm to centreline of slave pushrod = 118mm.

Distance from face of engine block to open end of slave cylinder = 22.8mm (excluding rubber boot).
Depth of recess in slave piston = 29mm.
Overall length of slave cylinder body = 108mm (excluding rubber boot).

Length of slave pushrod = 137.5mm.

Photos of components at https://www.flickr.com/photos/123675794 ... 123900401/

Having drawn out the critical dimensions in CAD, I reckon that three thick washers under the pivot post, raising it 7.5mm, would solve the problem, but that leaves less thread engagement than I would like, so I'd rather identify and fix the root cause.

JJMclure · Post by **JJMclure** » Sun Apr 20, 2014 5:57 pm

Correct master cylinder?

ngtcj · Post by **ngtcj** » Sun Apr 20, 2014 6:25 pm

JJMclure wrote:Correct master cylinder?

Thanks for the thought, but yes, the master cylinder is fine.

The problem is that even with the slave fully extended, the release bearing hasn't got close enough to the clutch. A different master cylinder couldn't push the slave any further than the maximum its already reached.

And to cover off some other possible issues that crop up, the clutch plate is installed the right way round and the gearbox shaft engages nicely with the spigot bush without binding.

Blown v8 · Post by **Blown v8** » Sun Apr 20, 2014 7:20 pm

I don't know the correct length of the pushrod,but I did have one that had been shortened !
Only found this out when I was having similar problems,so I bought a new pushrod !
How much longer would the rod need to be ?
I've rebated the flanges of a slave cylinder(about 8mm) before,to get a little of the "play" out

ngtcj · Post by **ngtcj** » Sun Apr 20, 2014 8:35 pm

Blown v8 wrote:I don't know the correct length of the pushrod,but I did have one that had been shortened !
Only found this out when I was having similar problems,so I bought a new pushrod !
How much longer would the rod need to be ?
I've rebated the flanges of a slave cylinder(about 8mm) before,to get a little of the "play" out

If 7.5mm difference at the pivot does it, then it would take 17.5mm at the pushrod, requiring one 155mm long. I've not seen any references to that long a pushrod on the SD1. It would be a solution, just as washers under the pin would be, but I'm hoping that before I resort to one of these someone who knows the Rover setup inside out can point definitively to something that is out of spec.

Denis247 · Post by **Denis247** » Mon Apr 21, 2014 3:58 pm

There's at least 2 different height pivot posts. It's a long while ago now, but I seem to recall having to swap these around to get my clutch working properly.