WINDOWSEET@aol.com wrote:
>
> 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
Greg,
You mention teflon valve seals. I have yet to see these advertised
or hear anyone mention where they can be obtained. Any chance you could
piont me in the right direction?
Thanks,
Bob Harris
|