Supercharger overhaul
T his month has been a focus on the old man’s Frogeye, as it’s not far from completion and it would be nice to get it done for the summer. With this objective in mind the 3000 therefore has taken a slight back seat this month. The dash and wiring are now in and the brake lines are all plumbed up, but the main obstacle to finishing the Frogeye has been the supercharger, which is taking a huge amount of time to get right.
This Shorrock unit is a lovely little piece of precision engineering, so restoring at home can be a challenge, but a bit of thought and methodical working and anything is possible! Last month I left off on the hunt for new bearings and thought this may prove to be a challenge, but a friend recommended a gearbox/motor specialist with a trade counter. A very experienced chap with a vernier caliper and a clutch of bearing books made light work of the problem. Twenty-four hours and £100 later I had a full set of super high quality bearings and seals. Result!
The next problem was fitting them, as each blower vane is on a yoke that has a bearing running on the main shaft. Pressing the bearing out was therefore not a simple operation – if the yoke was not supported it would bend – not ideal! To sove the problem I bought a length of aluminium bar from a local metal supplier and cracked open the lathe. I made a simple support to the outside and inside diameter of the yoke and then a series of lengths of bar that suited the each yoke aperture.
This meant I could happily press out the old and in with the new without fear of bending anything. I thought this could be the hardest job, but it was just time consuming. The challenge was the bearing on the drive plate – it was stuck
fast and had very little access to the rear of the bearing. I ended up carefully welding the puller to the bearing inner, but even then the force was so high the bearing material/parent metal gave up rather than let go.
Discretion is the better part of valour apparently, so a cup of tea later and out came the oxy-acetylene to lend a hand! I re-welded the puller, put some puller load on and heated up the old bearing. After a while you could hear it creaking then a ping as the puller load did its job. I had to repeat this process because as it briefly cooled it gripped again.
The outer race of the same bearing was also a bit of fun as it was pressed into a blind hole. I found a very large washer, turned it to the right diameter and welded it into the bearing, which meant I could tap it out from behind.
In the meantime I’ve been lining up the ancillary components ready for the charger. I found an old oil supply fitting and pipe in the stash of parts that came with the car. The braided hose was past it, but provided a good template for a hose specialist.
I have also been restoring the manifolds ready for a finished blower, which involved a bit of parts washing and blasting with a light media. I am glad I tried to get ahead of the game here, as I have just discovered the bespoke Shorrock manifold fouls my tubular manifold. Easy... re-fit the original cast exhaust manifold, you say? But that fouls too! Looks like more fun ahead getting the supercharger fitted to the car.
The challenge was the bearing on the drive plate – it was stuck fast