> Randall: You remark about the external oil feed to the valves, when I
> rebuilt my TR4 engine, I found that the rocker shaft had grooves
> where the
> rocker bearings rotated from a total lack of oil over a period of time. I
> installed an external feed to correct this. I haven't truly run
> the engine
> except for running in place (tub not installed yet), There is not
> evidence
> of exhaust smoke at this time. Also had the block dipped and decked.
Bob, this is my opinion, which obviously not everyone agrees with.
Unless the area was actually rusty, most likely the excess wear was due to
dirty oil (or simply old age). Unlike the rod and main bearings, the rocker
bearings do not require a constant flow of oil under pressure for normal
operation. They really only require a drop or two on occasion, which the
original oiling system was quite capable of delivering.
It's really not fair to expect the rocker bearings to last forever, and yet
some people do seem to expect that. Such a simple thing to do, and yet it's
frequently overlooked during an engine rebuild. Just like the crankshaft
and it's bearings, the rocker shaft & bearings do wear and need to be
replaced occasionally. I believe that will happen no matter how much oil is
forced through it.
Also, since there are no seals on the intake valves, there is obviously some
air movement through the space between the valve stem and guide during
periods of high intake manifold vacuum. If only oil is found at the top of
the guide, then it will suck oil rather than air. Again, a drop or two of
oil on occasion is beneficial (lubricates the valve guide) but a constant
flow results in excess oil burning.
Oil has an extremely low octane rating, so any oil that finds it's way into
the combustion chambers can induce knock. I ran an external oil feed for
awhile, which it turns out was causing knock during cruise conditions (when
I couldn't hear it), which eventually broke a piston. Not wanting others to
share my experience, I now recommend against the external oil feed (as do
many others that have tried it).
The original design is somewhat prone to getting clogged with sludge,
particularly if a poor grade of oil is used, or the oil is not changed often
enough. As part of my yearly lubrication routine, I now check that oil
flows the length of the rocker arm with the engine running. If it doesn't
within several minutes of starting the engine and letting it idle, then I
remove the rocker shaft and clean it. I've never actually seen the problem
on my engines, probably due to the oil I use, but I have seen it on almost
every engine I've bought, or seen others buy.
>From personal observation, Quaker State, Pennzoil, and STP are all very apt
to form sludge. I no longer use those products in my engines.
Randall
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