cautionary tale

I suppose you could do it that way, but I've been doing valves for almost
30 years and have never left the gauge in.

All I do is to make careful note of the position of the screwdriver slot at
the correct clearance setting, and make a tiny adjustment down to allow for
the slight gain in clearance you get when you snug the nut again.

 

That's also kind of silly (to my mind) because it's REDUCED valve
clearances that do the big damage. You can't hear reduced clearances.

 

That's also kind of silly (to my mind) because it's REDUCED valve
clearances that do the big damage. You can't hear reduced clearances.

 

I think it also has a lot to do with oil change intervals. The engine in
question may have had an inadequate frequency of oil changes.

 

I think it also has a lot to do with oil change intervals. The engine in
question may have had an inadequate frequency of oil changes.

 

head gasket,or valve cover gasket?

--
Jim Yanik
jyanik
at
localnet
dot com

 

That's also kind of silly (to my mind) because it's REDUCED valve
clearances that do the big damage. You can't hear reduced clearances.[/QUOTE]

Further proof that the marketing department writes the owner's manuals?

"Oh, look, the person who owns THIS vehicle will spend only $136 PER
YEAR in maintenance!!!" Yeah, right.

 

That's also kind of silly (to my mind) because it's REDUCED valve
clearances that do the big damage. You can't hear reduced clearances.[/QUOTE]

Further proof that the marketing department writes the owner's manuals?

"Oh, look, the person who owns THIS vehicle will spend only $136 PER
YEAR in maintenance!!!" Yeah, right.

 

Head gasket. The valves can't be removed with the head installed, and
that's the lion's share of the labor, usually. In addition to the head
gasket and labor, there may be valves that need to be replaced and seats
that need to be machined. If the head's off, resurfacing all the valves
and seats at the same time is moderately cheap and nobody I know "just
fixes the problem" while the head is off. Valve guide replacement costs
somewhat more, but if the valves have been sealing OK with the old
seals, then let the engine's age, the car's probable future life, and
your conscience be your guide.

Valve lash is both increased and decreased by engine wear.

At least three things can contribute to an increase in the installed
height of the valve. The first is normal seat and face wear causing it
to rise in the head. The second is wear at the junction between the
keeper and valve. The third, a particularly nasty problem that plagued
exhaust valves in older Datsun L-series engines run at high
(particularly, higher than recommended) engine speeds, is valve stretch
(culminating in stem failure at the keeper if you didn't catch it soon
enough).

Valve lash is decreased by an increase in installed height, and
increased by wear of the cam lobe, rocker arm, and lash pad. If the two
balance out, the lash will stay about the same essentially "forever."
If they do not, then it is helpful to know what is normal for the engine
you are working with. I have found our Hondas (late 80's, early 90's)
to be pretty balanced, rarely needing more than a thousandth or two of
adjustment for two or three valves at the Honda-specified intervals. I
don't know how later-model Hondas fare.

Although knowing what to expect can be important, a reasonably reliable
guide is consistency. If one valve is substantially different from the
rest, and the locknut wasn't loose, and it was about the same as the
others the last time, look further until you know why.

If you have time to burn, there is absolutely nothing wrong with
checking on things more often than recommended, and I used to do this.
These days, though, I treat my cars rather more gently (though not *too*
gently ;-) and have not had an engine problem in over a decade and a
half. YMMV.

 

That was my first thought, that the owner had run some additive-free,
buck-a-quart, SA rated oil, or hadn't bothered to change it at all. But
in that case, it seems you'd expect accelerated cam lobe wear that would
tend to open the lash clearance, if anything.

Does the minuscule volume of blow-by oil aid valve seat lubrication in
any way?

Regarding the original picture, I've got to agree with Jim, that lots of
high RPM and/or heat has worn or peened the valve to death. I'd like to
see pics of the seats too.

 

That was my first thought, that the owner had run some additive-free,
buck-a-quart, SA rated oil, or hadn't bothered to change it at all. But
in that case, it seems you'd expect accelerated cam lobe wear that would
tend to open the lash clearance, if anything.

Does the minuscule volume of blow-by oil aid valve seat lubrication in
any way?

Regarding the original picture, I've got to agree with Jim, that lots of
high RPM and/or heat has worn or peened the valve to death. I'd like to
see pics of the seats too.

 

I haven't seen a valve that bad since my brother in law pulled in the

Hey I resemble that remark, sold off my 1971 Fiat circa 1979
in just about that state! Replacedit for with Alfa and drove it until it
ate a (sodium-filled) valve about eight years later.

So far, in my experience, Hondas don't do that!

J.

 

I haven't seen a valve that bad since my brother in law pulled in the

Hey I resemble that remark, sold off my 1971 Fiat circa 1979
in just about that state! Replacedit for with Alfa and drove it until it
ate a (sodium-filled) valve about eight years later.

So far, in my experience, Hondas don't do that!

J.

 

the seats are fine.

the damage you see is not just heat [and definitely not peening], but
actual hot gas erosion. if you've ever used an oxy-acetylene cutting
torch, you'll have created gouges like this in the steel you cut, only
on a larger scale.

bottom line, there are actually two potential causes of this:

1. insufficient valve lash causing leakage, heating and then erosion.

2. defect in the valve - a "soft spot" could start the leakage, and
erosion takes hold from there.

#1 is completely avoidable.

 

the seats are fine.

the damage you see is not just heat [and definitely not peening], but
actual hot gas erosion. if you've ever used an oxy-acetylene cutting
torch, you'll have created gouges like this in the steel you cut, only
on a larger scale.

bottom line, there are actually two potential causes of this:

1. insufficient valve lash causing leakage, heating and then erosion.

2. defect in the valve - a "soft spot" could start the leakage, and
erosion takes hold from there.

#1 is completely avoidable.

 

well, provided the locking nuts are not crudded up, you can leave the
gauge in and the adjuster won't turn as you tighten the lock nut. makes
it a quick one-handed operation. if there's crud in the threads, you
need the screwdriver and two hands as you say.

 

well, provided the locking nuts are not crudded up, you can leave the
gauge in and the adjuster won't turn as you tighten the lock nut. makes
it a quick one-handed operation. if there's crud in the threads, you
need the screwdriver and two hands as you say.

 

My valve mechanism is squeaky-clean, with hardly any varnish, let alone
crud. I cannot tighten the locknuts without holding the screwdriver still,
otherwise the adjuster attempts to turn, even with a gauge in the way.
You're putting 18ft/lbs of torque on that locknut, which is sufficient to
push a lot of things around.

 

My valve mechanism is squeaky-clean, with hardly any varnish, let alone
crud. I cannot tighten the locknuts without holding the screwdriver still,
otherwise the adjuster attempts to turn, even with a gauge in the way.
You're putting 18ft/lbs of torque on that locknut, which is sufficient to
push a lot of things around.

 

my daily d15 is clean also, and the adjusters stay put as described.
the patient in the valve surgery case however, is crudded up, and a
screwdriver is essential.