Riley Pathfinder
Simon from Formhalls gets stuck into the Riley twin-cam
We left the 2.5-litre Riley engine last time in its constituent parts. It is only when you have something apart that you can really assess the condition of any engine. It was obvious the block would need a bore hone and skim at the very least. The cylinderhead would need, and indeed got a skim too along with the fitment of hardened valve seats that were reground in with all valves, springs and rocker assemblies cleaned.
The air intake and inlet manifold were cleaned and repainted. We then gathered all the bolts together and cleaned and refreshed them and fitted new block core plugs. Once the block had been bored out, we trial-fitted the pistons and set the ring gaps ready for assembly. We had also honed the small ends ready for the fitting of new gudgeon pins.
It all looked good, so we took it apart again for another clean. All engine covers were degreased and readied to be either machined and/or polished. Then the block was cleaned again and finally skimmed, rebored and honed for new pistons. Nibs were then adjusted for new bearings that were machined to suit. Nibs are the little grooves that the bearing housings use to locate the tab punched into the top of the bearing.
Suddenly we had an engine worth looking at, even in its exploded form. We cleaned it again ready for final paint and assembly.
In the end the block was painted in three coats of primer and five of colour. There was still machine work to do though.
The cam bearings were degreased bead blasted and polished. The same went for the timing gears.
The cams themselves have been reprofiled and hardened to ensure long service life, which is something we always try to do as part of any rebuild at Formhalls. The followers have been cleaned and polished as well, as have the push rods.
The sump was cleaned, blasted and scotch
brighted as well and was found to be sound – it will ‘go’ again.
The oil pump debacle
This started when we were trying to remove it from the block. Courtesy of an aluminium shaft sleeve in a cast iron block, along with many years of missed oil changes, this was more than a little stubborn to remove. Once that was out though, I had to strip it down. Initially it was a simple task: remove the pick-up strainer, pull off the base plate and drop the gear off the free shaft. Next came the driven gear. Referencing the workshop manual that we have for the engine it says to ‘knock the gear down to remove the spring clip and the gear will slide off.’ Simple, right? Or not.
After much trying and failing to expose anything vaguely resembling a clip, I then had the bright idea of trying to press out the shaft from the other way. This still didn’t work. The oil pump is driven off the camshaft, which itself is mounted up in the side of the block, a few inches below the deck. When you account for the length of the body of the pump, the drive shaft is about a foot long. So while trying to remove the gears, I put the full length under the shop’s manual press.
It didn’t go well from there on. At the top there is a bush and the main gear that supports and takes the drive from the cam. These are pinned and keyed to the top of the shaft. Hands up I hadn’t noticed this and sheared both of the pins and drove the key partly through the side of the gear. In doing so, I didn’t notice the bow that this had put in the shaft. I still hadn’t got the gear off the bottom either as this had a key in it.
I took a step back and looked at what was going on, swore, and after a bit of a chat, cut the gears off the top and dropped the shaft out the bottom of the pump. The angle grinder was deployed (quite satisfying) next to drop the shaft out of the pump and pull the gear off. Not that simple, as it required drifting off the shaft. Then I put the bush and gear in the lathe and bore out the remnants of the shaft – only then was I able to remove the parts. Then I ran a reamer down the gear and made a new bush for the body. Finally, I pressed out the old one and pressed the new one in.
A tough day at the office that one, but a good lesson for me. My boss, Charlie, was helpful throughout and it has certainly given me good experience to take back to Bicester Heritage, where I am part of the apprentice scheme.
‘A tough day at the office, but it was a good lesson for me’