Joe wrote:
> Could it be the tricked out engine that gave the smoke etc? Don't
> know, just asking. The only thing done to mine as a street cam during
> her rebuild (before I got her).
>
Not likely. Here's the thing about auxiliary oil feed to the top end.
Oil pressure is function of engine speed (to the extent limited by oil
pressure relief). In a stock engine, at about 4000 rpm, the amount of
oil pumped to the top end starts to exceed the draindown rate, so the
oil level within the valve cover starts to rise. Because iron valve
guide engines don't have valve stem seals, as the oil level rises to a
point above the top of the guide, the valve stems act like oil pumps,
forcing oil down the guides. This oil goes through the engine and out
the exhaust, which causes the smoke.
An auxiliary feed line simply increases the amount of oil available to
the top end, so this phenomenon occurs lower down in the rpm range, so
it happens much more frequently during normal driving.
This is true not just of Triumph engines, but of most overhead valve
engines. In fact, it's common practice on circle-track engines to
install oil restrictors in the galleries feeding the top end, since
excess oil causes drag and increases the likelihood of oil leaks at the
valve cover, which can get you black-flagged. There's little chance of
insufficient lubrication, because those engines typically operate at
80-100% of their peak rpm.
With my otherwise tired, but stock TR6 engine in the GT6, I can see an
increase in oil consumption on trips where the engine is steadily above
4000 rpm (this is easier for me to do than other people without
exceeding the speed limit, since the car has a 3.89:1 rear and no
overdrive).
The auxiliary feed line is basically a gimmick borne out of experience,
but for all the wrong reasons. Many Triumphs have succumbed to valve
train wear, especially on the forward rockers (the ones last in line to
get oil from the rear feed). This can be from excessive rocker-to-shaft
wear, allowing excess oil bleeding past the first few rockers, thus
starving the forward ones, or from the rocker shaft set screw working
its way out of place and falling into the pan. The latter is
exceptionally common, and will cause significant rocker wear. The other
perceived reason for thinking extra oil supply is necessary is valve
noise. Over time, the rocker face gets pounded down and/or worn,
creating a depression along the face. If the valves are set with feeler
gauges, the common practice, the valve clearance will actually be
greater than is indicated with the feeler gauge, so the valve clatter is
greater. The excess oil supplied by an auxiliary line tend to muffle
that noise.
So, adding the auxiliary line tends to mask or compensate for other
problems. Repairing the actual problem is the real solution.
Cheers.
--
Michael D. Porter
Roswell, NM
Never let anyone drive you crazy when you know it's within walking distance....
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