Cam bushes.

October 7th, 2014

One mod worth doing is adding o-ring grooves to the front cam bush (there isn’t quite enough space on the rear one). The bush fits into a hole in the crankcase so you can have oil flowing into the gap between the two rather than through the hole and onto the camshaft itself. There is just enough room for a groove between the locking hole and the front of the bush. I ground a tool and cut two¬†suitably sized grooves on the lathe.


The other mod is to restrict the oil flow through the bush. You can see the oil hole (the upper one above) is pretty large. You get way more oil going to the cam than you need meaning you don’t get as much going to the big ends where you want it. A well lubricated big end is a happy big end.

To restrict the flow you can fill the holes in the cam bushes with solder then drill a smaller hole. I filed the inside of the holes to get back to clean metal then used a small butane torch to solder the holes. After filling I carefully scraped and filed away the excess solder then drilled a 1/16th hole in each bush. I believe that’s the correct size.


I’ll put the bushes into the ultrasonic cleaner once I know that is the correct size to get them perfectly clean then bag them up until engine assembly. I won’t fit the o-rings till then. The other thing I will have to do is build up around the rear oil take off with a little epoxy then file it flat. This is so I can use a fibre washer on the rear oil take off to seal it.


The hose barbs I am using are parallel thread so they seal on the face rather than the threads as taper ones do (although some sealer on the threads might not hurt?).

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