Fitting Oil Pump and New Main Bearings
In part 1 of this project I said that originally I was hoping to re-use the original main bearings, as initially they had felt to be in good condition and there was no point replacing them if not required. However, in the process of removing the original bearing retaining plates - which I needed to do in order to get a good look at the bearings (and gave me the excuse to replace these original plates with my own bearing plates), I had found that actually there were tell tale track marks and pitting in the roller bearing, indicating it was scrap.
Even before I had looked at the drive side roller, I had removed the timing side bearing retaining plate, and a potentially more serious problem had manifested itself, in that just heating up the bearing plate with a blowtorch, so as to melt the solder had put enough heat into the crankcase that it had caused the timing side main bearing to drop out.
Normally a main bearing should only drop out once the crankcase had been put in the oven for some time, so this was not a good sign.

In the case of this engine, removing the oil pump first meant removing the two retaining screws then placing the crankcases in the oven to get them good and hot. Sometimes once hot the pump will drop out of its own accord, but in this case that did not happen, and therefore further encouragement was required. Sometimes you may be lucky and find the body of the pump has been threaded so that studs can be screwed in and a 1” x 6” placed over the timing case, to act as a puller by screwing nuts along the studs. In this case unfortunately the oil pump was not threaded and even with the crankcases ‘spit’ hot (stick head in oven and spit at crankcases. If the spit bounces back at you the crankcases are hot enough – use thick ovengloves or rags to remove crankcases, they are now very hot!) the oil pump was showing no signs of movement.

As is often the case, I found that the gears would not turn freely, even after cleaning, so I spent the next hour very carefully running a swiss file round each gear removing any signs of burrs or high spots. By the way, it is important when stripping pumps to ensure you note which way the gear sits, relative to the pump body, so you reassemble in the same plane as you stripped it. The reason for this, is that you can find that the gear occasionally ‘flattens’ at the end it touch’s the end plate, and therefore the gears become ‘sided’. I confess I forgot to do this in this case, so had to be extra careful when I re-assembled until I figured out which side went where (you can sometimes see matching wear marks on corresponding gears – I tend to use an eyepiece to check). After what seemed a very long time, the gears were able to slide back into the pump far easier and gently revolving the pump drive with a suitable drive tang (an old oil pump drive plate is good for this) gave that lovely satisfying feeling of gears revolving smoothly together. The last step of the refurnishing process was to take the brass side plate (the plate that the drive shaft fits through) and remove the score marks where the oil pump gears have been revolving. I first of all put this plate (carefully) on my linishing machine, using a fine belt, until all traces of the scoring are removed. I then put it on a surface plate using fine wet and dry (with light oil sprayed on it) for the final clean.