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M32 Pushrod Tube Fix

Started by Hamwic, 17 Oct 2020 at 19:24

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As some of you may recall, I have been trying to come up with a way of getting some much needed lubrication to the pushrod ends of the M32. The evidence of bad wear and poor lubrication meant that something had to be done. Loading the rocker box with LMP grease would probably only result in marginal and occasional lubrication of the vital parts, and if it got hot enough, the surplus would eventually run out of the holes at the bottom of the pushrod tubes where the tappet block clamps locate.

These tappet block clamps are standard sidevalve ones, and straddle the locating groove for the bottom of the tubes. It seems that in the past these have damaged the grooves, and the force required to unscrew the tubes to access the tappets has mangled the end notches, as they are very thin.

There would be no point in introducing any lubricant if it just ran out of these gaps.

Having re-tubed the pushrod tubes by cutting off the threaded portions and silver soldering them to some new tube, and making up some new locknuts, it seemed a shame to machine the necessary slots in the bottom. This fix has suggested itself, and I think it's going to work. It may also stop/slow leaks from the tappet ends, as unlike on a sidevalve, surplus oil from here can't easily be pressed into service.

The bottom of the tubes is left as tube with no notch, and the tappet block clamps are reduced in length to just locate outside the groove where the tube sits. The clamp can still press the blocks in, but not obstruct the tube. This was achieved by simply welding inside the folded ends and grinding them back to re-form the contacts at the necessary pitch.

Holding the tubes for slackening the threads can be achieved by using a Jubilee clip around the tube, and using the appropriate tiny C spanners on the lock rings.