[BOUNCE triumphs@Autox.Team.Net: Non-member submission from ["Robert M.
Lang" <blang@MIT.EDU>]]
Date: Tue, 30 Dec 1997 10:56:35 -0500
From: "Robert M. Lang" <blang@MIT.EDU>
Subject: Re: Unleaded Gas
Hello folks.
Hopefully, by the time you read this the discussion of unleaded fuel and
Triumph engines will have slowed down - a bit. But I need to air my two
cents worth.
I see three possible scenarios:
1. You have a car, you drive it.
2. You have a car, the power is down a bit and you decide to "freshen" the
engine.
3. You have a car, the power is way down and you to a leak-down and
discover that the head has problems (blow-by on one or more valves).
In each scenario, the owner has to make choices about how to fix things up
given that unleaded fuel is the only fuel available. Now, the folks in
Europe are repidly approaching the situation that we've had hear in the
states for over ten years - the phasing out of lead in fuel.
In all three scenarios above, you do not need to replace your valve seats
UNLESS YOU HAVE MEASURABLE VALVE RECESSION.
Take my advice: don't waste your money on hardened seats unless the valve
faces are flush with the combustion chamber. By installing hardened seats,
you are doing several things: one you are doing unnecessary work on your
head. You are adding a potential failure point (ref. Mr Guyot's valve seat
failure) and you are spending money that you don't need to spend.
As for driving at 55 m MPH, I have news for you. I've put close to 60,000
miles on my TR6 since they stopped allowing lead in the US. I have had no
problems with valve recession in my car. I've had the engine apart several
times and measured everything and there is no appreciable wear. Oh, I drove
over 5000 miles round trip to Ft. Worth, TX for the VTR at considerably
over 55 the whole time - more like 70 mph or more as that is the posted
speed limit on the other side of the Mighty Mississippi. Well, I admit - I
drove like I was in Texas the whole trip. Shucks. Less than 24 hours
driving on the trip home.
And I drive my car pretty hard. Come for a ride with me some day and I'll
show you some twisty little New England Roads at appreciably more than the
posted speed. And I race my car in local Autocross events at least 10 times
a year (more if my car is not torn apart). So, it would be safe to say that
I represent the upper threshold of applied engine stress...
Now, don't get me wrong - if there is valve recession, there is not a lot
of choice about new valve seats. But if you don't need them - why bother?
As for valve guides - that's another thing that you don't need. The stock
cast iron valve guides are plenty servicable for a long time. If you have
the head off the engine and you do a valve job, if the valve guides are
worn - then replace them. If you do a lot of FULL THROTTLE driving, then
you should consider the silicon-bronze replacements. If you drive more like
your grandmother (well, not like my grandmother - I'd have put the
silicon-bronze valve guides in her car) then the cast iron stock valve
guides are plenty adequate for a long service life - maybe over 100k miles.
I'll let you know when I finally replace mine - they only have 98,000 miles
on them and they are still okay.
Bottom line: Triumphs work fine with no-lead - really. And I'm not some
tree-hugging, save-the-whales type. If you really beat on your car, then
you might need the "full treatment (silicon-bronze valve guides and
stellite seats)", but for most of us, the stock setup is just fine for a
long life.
And, keep in mind that a lot of folks with these cars only drive them 2k
miles a year. That's 50 years of service on a standard valve job. Why pay
more money when there will be no return on investment??? I put over 9k
miles on my car this year and at that rate I shouldn't need another valve
job for about ten years.
Food for thought.
regards,
rml
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