SOHC.co.uk Forums > The Black Bomber Board
450/500T Startup
the-chauffeur:
No worries.
I'm pretty sure it's Tom (AncientDad) over at the VHT forum who made his own - either that or he linked to the thread where that was discussed at a time when the HT forum search function still worked ::)
I ended up buying one of the Cappellini baffle plates a while back. Nicely finished but not cheap for what it is (and the fact that the UK importer is pretty much hopeless doesn't help). As I've found out more recently, they're very sensitive to placement - I've managed to shave down one of the edges because the plate was fractionally to close to the side of one of the cam lobes. Trouble is, it's virtually impossible to see whether it's fitted correctly - you've just gotta put it in place and sort-of hope for the best.
I've kinda gone off the idea of the bearings for now. Can't remember the reason off the top of my head but it's something to do with the machining down of the journal ends. Might end up going for one of the oversized standard oil pumps at some point, but right now I'm more concerned with trying to iron out fuelling issues following a Mikuni carb swap.
K2-K6:
"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."
I feel that this overall assessment appears more of an "assumption" within the community that run these engines. Certainly it would be foolish for me to claim that less oil for anything like this could improve longevity, but it just doesn't appear to be the root cause of failure, time of supply, that is. If you run many engines with covers removed to see cam supply I think you'd be surprised at the time it takes to fully establish significant oil level to these components.
Diluted oil, certainly, that's simply making a reduction of both film strength (principle requirement here) and will ultimately give reduction in oil pressure (affecting pressure fed areas and components) also to drain away from top of engine faster than design intended. Of course, the speed it drains from pressure controlled areas affects how long it takes to arrive at the furthest extremities too. To me, dilution is all undesirable.
I'd question the logic of increased pump size as the system pressure ultimately controls the flow when considered at the oil viscosity that you pump. The excess has to be dumped via the pressure relief valve, and so does nothing to improve the supply. Think Jensen has data for this on twins forum. The pressure relief valve is after all there to save the oil pump drive on any engine. I don't see any gain, just more delivery and more blown out the valve.
The simple answer to viscosity at lowered temps is to reduce the "w" number specification on oil used as that ultimately controls the speed at wich the oil travels within a system at standard specification. A 0W/30 would do this, which is not as many would interpret :) but it would reduce the cold viscosity and simply arrive at destination faster.
The true cause of the cam wear on these appears to originate with exhsust cam clearance. Again, Jensen has some very accurate record of what happens here. I believe he has that correct. When you compare the observation about oil arrival time in seconds to the amount of seconds of engine run time, well it's actually a minute segment proportionally. 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.
SeanFD:
--- Quote from: K2-K6 on October 06, 2020, 11:22:24 AM ---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.
--- End quote ---
I followed what you were saying up to this point. If I get you right, you are saying that the valve (stem, seat. what?) simply wears the other components (combustion chamber seat, guide, small rocker pad?) to the size and shape it needs and in order to do so removes any oil that gets in the way, thus reducing lubrication and increasing wear?
I have just spent several weeks trying to sort out the top end on a 450K1 which was lacking compression https://www.vintagehondatwins.com/forums/showthread.php?2045-Dry-Cam-Chain-and-Rockers! without success because one of the valves is bent.
I read quite a bit about wear and tear of the cams and rockers and would therefore like to understand the process.
taysidedragon:
I don't know these engines, but I assume they don't have an oil bath like the 400f.
That holds some oil in the top end and as soon as the camshaft rotates it dips into the bath and picks up some lubrication until the cavalry arrives from the oil pump.
Is there any way of modifying the 450 head to hold some oil for the cam?
Skoti:
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?
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