Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
Ash - I've just found an old thread where you were pondering a roller bearing conversion on a 350 engine. Did you ever get anywhere with it?I'm asking because I'm considering going the Cappellini route with a 450. I'm a little paranoid about the fragility of the exhaust cam and so along with the conversion kit I'm thinking about adding the oil filter kit, oil line and bored out/bigger oil pump piston mod. Yes, that's probably overkill for a road bike, and yeah I've probably got more money than sense . . . but given the lack of liquid cooling in the 450, I don't like riding in modern day city traffic on a bike designed for 1960's roads because of the stop/start nature of the journeys I do. I want to keep heat to a minimum and I suspect the rollers will help. K2-K6 - would the fact that the 450 cams are suspended at height with no access to oil until it's forced round by the pump make any difference to lobe wear from start-up? In the case of the nearside exhaust lobe, received wisdom is that it can take anything up to 90 seconds for oil to get to that point from cold (I have no idea how true that claim is). Given the oil will also be at its thickest when cold and that's likely to reduce its spray coverage, that's gotta be tough on that lobe. It's not a phenomenon that seems to happen much in other similar bikes and I'm wondering whether that's because most have oil baths immediately below the cam lobes that offer even very small amounts of lubrication until oil starts being pumped/sprayed about. Couple that with your theory about oil condition/contamination and I guess it's easy to see why the 450 exhaust cams fail so regularly.
The characteristic of how the clearance is adjusted in this design appears to remove any wear items that would at least mitigate valve seat wear. In other words, a virtually perfect engineering concept, or close to it. The valve, in moving toward the operating mechanism simply removes the tolerances it needs, again Jensen's data would seem to prove this. That will ultimately compromise any valve gear system, ie. Losing clearance as it destroys oil film for literally every rotation the cam completes. Jensen watches those clearance like a hawk and I believe that's the answer.
Gareth,I'm don't know those engines either, but would the 'oil flow conveyor, exhaust camshaft' pictured earlier in this thread be the answer?