Wednesday Afternoon
10 September, 1997
12:57PM CDST
Hi, Dave;
The issue isn't the oiler. It is definitely the valve guides. The Triumph
guides weren't designed for a lot of oil in the rocker area because they
don't have seals of any kind. I suspect that one of the reasons Triumph
engineers restricted the flow of oil to the valve train is because they were
trying to cut down the amount of oil that found its way into the guides. In
the process they doomed the rockers and rocker shaft to a short life. Some of
the approaches they took in engineering the engine doesn't make sense. Since
it is a cast iron head they could have eliminated the valve guides altogether
and let the valves ride in the cast iron (pretty common on US V-8's). Then
they turn around and run the cam in the cast iron block without bearings. Now
that is a puzzle. On my first GT6+ one of the valve guides worked itself
loose, cracked into pieces and trashed the cylinder.
The key to a successful exterior oiler for the head is having a fresh set of
valves and guides or ones that have had teflon valve guide seals installed.
Another point of note is that most V-8 engines don't have rocker shafts,
instead they have pedestals and the wear is reduced by heat treated stamped
steel rockers and hardened pedestal bolts. Rocker shaft wear doesn't even
enter the picture. I suspect that all the rocker shaft wear we are hearing
about in many of the current posts is due to insufficient lubrication
combined with inadequate heat treating on the shafts. The factory service
manual says that "To prevent excess lubrication of the valve gear a scroll
and two flats on the back fo the camshaft meter oil to the rocker shaft. That
means that the front of the valve gear will get less oil than the back
because ports in the rockers let oil from the rocker shaft lubricate the
rocker pads. Therefore the pressure and volume of oil drops as it passes each
port.
I would think that the area to attack would be the flats on the camshaft in
order to re-engineer the problem. But that would also necessitate valve guide
seals (which I believe is a good move in any case) to prevent leakage of the
increased oil into the combustion chanmbers. The reason I recommend
modification of the cam is to put more oil into the space between the rocker
bore and the shaft. I don't know that the exterior oiler does that. From what
I can see it would benefit the rocker pads, pushrods and lifters but I would
think that the pressure from the oil coming out of the shaft would prevent
the lubrication from the external oiler from permeating the rocker bore.
This is ironic because the major problem in Chev V8's is having too much oil
in the rocker area and not nearly enough in the lower end of the block. There
has been much written about using oil gallery plugs to limit the amount of
oil that goes to the valve train on a V8 and redirecting it to the main
bearings.
Fixing the problem on the Triumph 6 would involve a lot of trial and error in
welding up and remachining the scroll and/or maybe just modifying the flats
to increase the flow of oil to the valve gear. Obviously, no one has tackled
this yet....or at least I haven't heard of it.
Maybe some of the other listers can add their logic to this problem but for
the time being the exterior oiler on an engine with fresh valves and valve
guides (and seals) is the only solution to valve gear wear.
Good luck in your preparations for this weekend's race. I'll call you
tomorrow to see if I can lend a hand.
Greg
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