<VV> Lifter operation

[Roger Gault]

The issue that's not being mentioned here is that the Corvair lifter is on
it's side.  When the oil flows into the "botom" chamber, the air has to come
out.  If has to go into the "upper" chamber and be flushed away by the oil
flow "up" there.  The problem is, that isn't "up" there - it's "over' there.
The air has no place to go.  The openings are through the checkvalve and
through the clearance between the lifter body and the piston.  The piston
clearances are long, really tight, and full of oil - the air has a tough
time pushing out there.  In the standard SBC orientation, the "bubble" of
air is up by the checkvalve, and can leak past the seat pretty easily.  In
our engines, the checkvalve is covered well before all the air is out.  This
is why it's so hard to get our lifters pumped up.

When we're driving the pump with a drill, it is basically impossible to fill
the lower chamber.  If we get the oil up to 30 psi, then we can squeeze the
air volume down to 1/2 its original size (and the lower chamber 1/2 full),
but that's all.  Both "exits" for the air are at the same pressure as the
trapped air, so it's not going anywhere.  When we stop pumping, a little of
the air might escape.  If we cycled the pressure a number of times, we might
get most of it out, but we'd have to let the lifters bleed down between
cycles, and we don't have enough patience (or beer) to do that.

So, if you want your lifters pumped up quickly, do it before you install
them.

Roger


----- Original Message ----- 
From: <BobHelt at aol.com>
To: <chsadek at comcast.net>; <mark at noakes.com>; <virtualvairs at corvair.org>;
<vairologist at juno.com>
Sent: Saturday, July 21, 2007 1:36 PM
Subject: Re: <VV> Lifter operation


> In a message dated 7/20/2007 8:40:21 AM US Mountain Standard Time,
> chsadek at comcast.net writes:
>
> With all due respect, Bob, not true. That is not how current  hydraulic
> lifters work.  I have OBSERVED the oil going to the  rockers, while
priming.  You
> need to disassemble a lifter and take a look  at how it meters oil. I
have.
>
> Chuck S
>
> And.....
>
>
> Smitty Says:  You are usually right about things Bob but not this  time.
> Better go to the garage and take one apart yourself.  I don't  think
anyone has
> done more hours of research trying to find out how lifters  operate in the
last
> three years than I have.  I lost three sets of heads,  thousands of
dollars,
> and in effect, an engine because of the crappy SBC lifters  we are pretty
much
> forced to deal with.  I have torn down more lifters than  I would have
> believed existed and they all have one thing in common.
>
>
>
> Hi Guys,
> I can see that despite your many years of experience and disassembly of
many
> lifters, you both still have an incomplete understanding of how a lifter
> operates. So please allow me to enlighten you so you will know.
>
> There are two oil compartments within the SBC or Corvair hydraulic
lifters.
> The upper one receives the flow of oil from the gallery and is filled with
oil
>  by the pump oil pressure. To get any oil into the lower compartment, oil
> must be  forced past a check valve. This requires some oil pressure to
accomplish
> and  only occurs after the upper chamber is completely filled. This is
done
> by  use of a metering valve at the top of the upper compartment. When the
> lifter is in operation (engine running) this metering valve is thrown by
inertia,
> first, up against its upper seat (lifter moving down). This   blocks-off
any
> flow to the pushrods and rocker box allowing the oil pressure to  force
oil
> into the lower chamber. The point here is that unless this flow to the
pushrods
> is blocked-off, the oil won't be forced into the lower compartment.  Then
> when the lifter is moving up, the metering valve is moved off its upper
seat by
> inertia and the oil flow is diverted to the pushrod instead of the lower
> chamber. This lower chamber by the way is what fills with oil to raise the
> internal piston to take up any slack in the valve train.
>
> So if you both are correct and you have just installed a new lifter, or
> lifters, without first filling them with oil, both chambers are basically
empty
> (maybe containing a little kerosene, and maybe not). So when you  finish
engine
> assembly and use your electric drill to run the oil pump, you want  the
> metering valve to be pushed up against its upper seat so as to force oil
into the
> lower chamber. However, as you both assert if THIS DOESN'T HAPPEN, then
oil
> is now allowed to flow only into the upper chamber and from there to the
> pushrods and rocker box, where you now observe it. The problem here is
that if  the
> metering valve is allowing oil to flow to the rocker box, then little if
any
> oil is actually being forced past the check walve and into the lower
chamber,
>  pumping the lifter up. No oil in the lowed chamber means the lifter is
not
> pumped up.
>
> So AGAIN, I suggest that watching for oil dribbling out of the pushrods
> after installing new lifters and running the oil pump with a drill motor
is NOT
> the best way of assuring yourself that the lifters are pumped up. You are
only
> seeing oil that has flowed into the upper chamber and then into the
pushrods,
>  and little if any going into the lower chamber. You certainly have no
way
> of knowing how much oil is being diverted (if any) into the lower
chamber.
>
> Regards,
> Bob Helt
>
>
>
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