<VV> Valve adjustments

[Mark Durham]

Kirk, I'm pretty sure all the other guys are trying to help, however, in
their exuberance to show their point, its gotten confusing. Bits and pieces
are correct but not in the same email.

You adjust the valves once and leave them alone. The only reason to readjust
is if something breaks, like a lifter quits working, or if you have wear in
the system, like a cam, lifter, or rocker arm wear. Or, you have one making
noise and you want to find it and see what is going on. Sometimes its a bent
push rod (at which point adjustment won't help), or, the engine is new and
being set up.

My procedure:
If you are assembling an engine, you can do a cold adjustment to be close. I
use as close to zero lash at TDC compression stroke for that cylinder I can
get, by feeling when the rocker gets snug as you tighten the nut, then go in
1/4 turn. Then start and run the engine and when warm, adjust out until the
lifter clatters then in until zero lash, then make your final adjustment.

The book says 1 turn in past zero lash, and I suppose that is OK, however,
I've also been told by several Corvair mechanics that worked on lots of
engines that 1/4 turn is sufficient and if you go more it puts additional
load on the lifter and cam lobe. I was told this by a local Corvair mechanic
when I had my first one back in the 60's. So, I've always used the 1/4 turn
method and put upwards of 80-90K miles on the engines without another
adjustment.

However, the only extra pressure I could think going the 1 full turn might
place on the system is from the spring in the lifter and that becomes a moot
point when the lifter fills with oil and locks in place by the check valve.
Maybe that is enough to cause extra wear, however, I can easily push in the
plunger when there is no oil in the lifter, so the extra pressure would be
nil, in my mind.

All the spring does is hold the cup up against the push rod until the oil
fills the lifter body. That locking action happens each time the car is
started and oil pressure is applied to the lifter body so it automatically
adjusts for wear on its own to zero lash.

For as long as adjustment takes, you could just run the engine until warm,
shut down, then remove the valve covers, start the engine, and quickly do
the adjustments, and let the oil drip, however, its better to cut a valve
cover down into two one third pieces,or get the one from Clark's with holes
in it. There may be a few of these laying around with members of your local
club, or maybe someone from the forum will allow you to borrow his/hers.

Make sure you do not turn in the nut more than 1/4 turn at a time, because
with the engine running, it has to compensate for the extra oil in the
lifter body and will keep that valve open for a few revolutions as it
compensates (engine will run rough then go smooth when it is done
compensating).

If you are doing a new engine and just adjust the lash to 1/4 turn, you may,
after the break in period, have to readjust due to the normal "wear in" of
all the valve train components.

So, its up to you to decide if you want to use 1/4 turn or the book value of
1 turn, or something in between.

I know what I was told, this was a Corvair only shop, and the two brothers
were experts, but it might be a wives tale, or maybe there was a round of
bad cams or lifters in the 60's. I also have applied engineering logic to
the valve train and can find no reason why adjusting to 1 turn would be
hurtful to your engine. It just pushes the plunger 3/4 of a turn further
into the lifter body. This would also compensate for more wear and tear on
the system over time, (a good thing, if you don't want to know).

Hope this helps :):)
Mark Durham




On Wed, Aug 25, 2010 at 7:08 PM, Kirk Johnson <
ragstheratrodrampside at yahoo.com> wrote:

> How often do you folks adjust your valves???
>
> Kirk Johnson
> 1964 Rampside
> De Soto, Kansas
>
>
>
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