Hi,
Tony, maybe you can clarify a little on what you've been doing when setting up
your engines... And perhaps I can add a bit about?a?possible?reason?this
happens...
My understanding is that the "unleaded" bronze valve guides we?have to
use?today tend to expand more with heat than the originals "leaded" ones?did
(cast iron of some sort, I believe).
As a result, it's an all too common mistake to "follow the repair?manual specs"
when honing the new guides, which will leave the bronze ones?far too tight once
the engine has warmed up. This?can lead to stuck valves?or worse.
Now, I don't have a repair manual at hand, but seem to recall that the original
specs for honing showed a range and?with modern guides you'd better?NOT hone
for the minimum. Instead hone for the largest dimension shown.?On the
original?guides the larger dimension?would have indicated wear, that?the
guide?was reaching the end of its useful life and would soon need replacement.
But, again, with modern guides it's best to hone for the largest dimension
shown, or you?may see the valves start sticking.
Can anyone check confirm the original TR2/3/4/4A?repair manual specs for valve
guides, especially on the exhaust side (if it differs from the intake)?
The most likely valves to stick with the too-small dimension are the exhaust
valves because they have to deal with considerably more heat.?And, yes as Tony
points out, #4 is the one that tends to run hotter on a TR engine,?even if
it's?seen some mods to improve coolant flow back to the rear of the engine &
head.
Alan Myers
San Jose, California
amfoto1@aol.com
'62 TR4 CT17602L
http://www.triumphowners.com/640
-----Original Message-----
------------------------------
Message: 3
Date: Sat, 19 Sep 2009 11:51:19 -0500
From: Tony Drews <tony@tonydrews.com>
Subject: Re: [TR] Sticking Valves?
To: Michael Lang <mlang99@comcast.net>, triumph list
??? <triumphs@autox.team.net>
Message-ID: <20090919165151.73ECF187644@autox.team.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed
The valve guide clearance is a key factor in our engines.? With too
small clearance, we have stuck valves in racing conditions -
especially when the engine starts running hot.? With a high lift cam
so the valve can potentially hit the piston, the result is
disastrous.? With the stock lift, there shouldn't be interference, so
the result is much less catastrophic.? The #4 cylinder is more prone
to run hot than the other cylinders.? So, your theory is
plausible.? BTW, we specify 0.004" with new guides.
Normally I would suspect a fuel delivery problem, but the "valve
train clatter" is suspicious.
- Tony Drews
At 11:32 AM 9/19/2009, Michael Lang wrote:
>I have now got about 2000 miles on my freshly rebuilt TR3 engine and am
>having a sporadic problem. I drive a lot of hilly back roads on the way
>to and from work. When I climb one particularly long hill at about
>65mph, the engine starts missing on one cylinder and I begin to hear a
>lot of valve train clatter. If I back off a bit, it stops missing and
>runs fine. It continues for such a short time after reducing load that I
>have never been able to stop and diagnose the problem.
>
>When I rebuilt the engine, I had the head done with new valves, bronze
>guides and hardened seats. I think that I have a valve that is sticking
>when running hot under load. Is this a common problem with these
>engines? Any other thoughts an what might be happening?
>
>Thanks,
>
>Mike
------------------------------
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