Thwaites 4WD 3T Dumper Restore

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Re: Thwaites 4WD 3T Dumper Restore

Post #21 by cobbadog » Thu Aug 09, 2018 5:36 am

Yep, those are the 'dots' I mentioned when assembling the pump on the big CD 8hp Lister. Thanks Fred for posting them.

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Re: Thwaites 4WD 3T Dumper Restore

Post #22 by swalshire » Sat Aug 11, 2018 1:22 pm

Thanks Men, got the shafts out & re-aligned via the threaded bar & oversized socked approach. By Joe there were well tight, a slow job. Anyhow, next question, the book says during refit the leaded wire used to measure the internal gap from piston to head should be 0.813-0.889 mm. This is measured by putting a piece of solder wire there & measuring after 2 revolutions.

If I dont use any gasket or shims I get a lead thickness of 0.8mm, is the figure in manual correct ?

During stripdown there was gaskets & shims present on all pistons, without shims & gaskets isn't the valve going to hit piston ?

Is the wire flattened by the piston against the valve or piston against the head ? I don't have the valve pushrods fitted to rockers during my measurements.

Guys just to follow up on this, I have it sorted, I mis-read the intention of the manual, the solder wire is not placed at either end of the gudgeon pin end sides, it is placed 90deg opposite (put one of camshaft side, put other on exhaust manifold side, that way the pistons do not interfere with the wire during its compression. That way the gap is measured from piston top face to cylinder head face (google bump clearance). The gap as stated in manual IS correct. Also I used 0.5mm solder wire wrapped to look like a coil spring. Got consistent results with it.

I left my original questions there in case some other member comes with the same query. I'm learning all the time on the re-build

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