At 09:51 AM 3/2/99 -0600, Bill Eastman wrote:
>....
>On a side note, I put new exhaust valves in last year without hardened
seats. As long as I take it easy, I am OK but at higher speed the valves
can close up in a hurry. If I run 75 miles at 75 (OK I push my limits
occasionally) I have to adjust the valves. I will probably have hardened
exhaust seat fitted this fall or sooner if do a lot of longer trips.
>
>How about some other input? What do you do, Barney?
I use hard steel valve seats and stellite exhaust valves and run the crap
out of my MGA trailer towing and autocrosing. Early on I ran standard
valves and seats, and I did notice some valve recession, although not
nearly as fast as you mention (above). I once ran 13,000 miles (towing the
trailer) in six weeks, mostly with the cruise control set for about 75 mph
(4400 rpm). I adjusted the valves once early in the trip because of low
clearance (residual from prior mileage), and then again about 2/3 of the
way through the trip to take up a few thousandths more.
My first change was to hard steel seats when the 3rd or 4th valve lash
adjustment bugged me, and I had the head off anyway for a touch up of the
exhaust valves. I have since put another 100,000 miles on that head, and
the hard seats are still doing just fine. In fact, with just a minor touch
up to narrow the exhaust seat lands a little, that same head has now been
swapped onto another fresh engine for continued service. In short, I am a
firm believer in the economy of hard valve seats.
In the meantime, the same engine had gone through two sets of standard
exhaust valves in about 50,000 miles, and the iron guides were getting a
little loose (but not terribly bad). I then installed bronze valve guides
and stellite exhaust valves, which have now run over 50,000 miles. The
bronze guides still look like the day they were installed, and the exhaust
valves are only about half used up. So, for my kind of vigorous driving,
I'm also sold on the economy of these special parts.
>Lawrie, how often does a B series MG engine show up with a thrown rod or a
dropped valve?
Well hey, my first MGA dropped an exhaust valve two weeks after an engine
overhaul with all new valves. Four or five years ago my current MGA also
dropped an exhaust valve. Both times I was just cruising at about 60 mph
on the open road when it happened. That in itself is no coincidence, as
most of the mileage is on the open road. However, both of those incidences
were with standard exhaust valves, and I have yet to drop a stellite valve
(knock on wood). If that should ever happen I will certainly let y'all
know. But for the time being, my ego thinks the stellite valves are
somehow tougher in stress resistance, as well as more heat and wear resistant.
>Personally, I think that highway running is about the easiest thing we do
to these cars.
Ye speak fer yourself, Bill. Have you seen the "Trailering in Montana"
picture on my web site? I had the tach well above 5K and the temp gauge
nigh well pegged all day long. I'm sure that prolonged driving like that
contributes heavily to valve wear. And then all those gravel "highways" in
Canada and Alaska seem to have eaten the top rings off the pistons in a big
way. Anyone have an opinion on chrome faced rings for the top groove? Or
will this be something else I have to research on my own? I reckon my next
step is K&N air filters.
>....
>Bill Eastman
>61 MGA who likes to be given a little reign and would much rather blow up
at 75 than be forced to run at 55.
Amen to that,
Barney Gaylord
1958 MGA with an attitude (and no respect whatsoever for engines,
gearboxes, brakes tires or fuel economy, other than to keep up a good
maintainance program and have confidence)
http://www.ntsource.com/~barneymg
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