Advanced Engineering Tech - Lilfter Preload vs. Pump Up

Is lifter pump up a function of preload and RPM or RPM only?

I would say just rpm as far as pump up is concerned with regards to the two items you've asked above. If you are talking about the lifter compressing then maybe pre-load would be something to look at as well as not enough may allow for compression to occur druing the lifting of the valves. Also, something else to consider would be if not enough spring pressure is used the lifter may pump up as well I would think as not enough pressure will be there to hold the pushrod against the cup as the lifter travels over the centerlines of the lobes and back down the lobe. I'm sure the experts will chime in here in a second though. Should make for an interesting thread.

Maybe I can clairify, if I understand your question correctly.

Lifter pump up is a process that occurs with every start-up to some degree. Every time the engine is stopped, the valve springs on the valves being lifted by the cam lobes are pressing against the oil pump plunger/piston built into each hydraulic lifter. In time, this squeezes the oil out of the oil chamber in the lifter and there is slack in the valvetrain. On the next start and warm-up cycle, the the lifters pump-up (fill the oil chambers with oil) this is due to the oil pressure rise from the main oil pump and the plunging/pumping cycles within the lifters themselves due to actuation by the cam.

Pre load is akin to setting the valve clearances on mechanical lifters. Net or zero lash ocurs hen the heel of the cam is against the lifter (no lift applied) and there is no slack in the valve train (rocker arm to valve, rocker arm to push rod, pushrod to lifter, and lifter to cam lobe. Also, the piston/plunger within the lifter should not be compressed, thus squishing the oil out of the oil chamber. Once zero lash is determined, if you have adjustable lifters, you can now set the pre load with the adjusting nut ant lock it down. Alternately, if you have non-adjustable lifters, you can adjust the pre load by a combination of selecting the correct push rod length and shimming the rocker arm base if necessary.

I hope that this helps.

Steve

I was under the impression that pump up, atleast atleast in the context of the question that is being asked, is the plunger in the lifter actually moving up relative to the body of the lifter during the time the lifter stops lifting (once it has reached the centerline of the cam lobe) and starts going down the down side of the cam lobe.

I have been reading in several threads that too much preload results in pump up and holding the valves open. Some have found too much preload on the Morel lifters have done this, and some with stock. I thought pump up was the result of the onset of valve float, not vice versa. Everything I have read in technical articles states that pump up results from slop in the valve train usually when the springs can't keep up and the lifter tries to take out the slack. But many threads on this forum are indicating that lifter preload can cause pump up to occur.

I have been reading in several threads that too much preload results in pump up and holding the valves open. Some have found too much preload on the Morel lifters have done this, and some with stock. I thought pump up was the result of the onset of valve float, not vice versa. Everything I have read in technical articles states that pump up results from slop in the valve train usually when the springs can't keep up and the lifter tries to take out the slack. But many threads on this forum are indicating that lifter preload can cause pump up to occur.

I wonder if more valve spring pressure would also help solve the valve float issues here? Ofcourse just reducing the pre-load, if it fixes the valve float/pumping up issue, would be a lot easier and cheaper.

I think this is the root of my question, is pump up the cause or the effect. Recent information about altering (lowering) preload providing better RPM capability makes me wonder.

I think this is the root of my question, is pump up the cause or the effect. Recent information about altering (lowering) preload providing better RPM capability makes me wonder.

Ahh.... I see. Yeah, maybe there is something there. I guess one thing to note would be that too much pre-load may really load the spring underneath the spring cup and make it try harder and harder to push the spring cup back out, specially during the time when the lifter travels over the lobe centerline, which would result in this "pump up".

In my opinion, the main danger of too much pre-load is that the valves can unseat when on the heel of the cam, cutting compression, reducing power and burning valves. Too little pre-load and the valve train is noisy, wear is increased and you don't get full valve lift.

Steve

Too little pre-load ... wear is increased and you don't get full valve lift.


I'm not sure I understand the reason for not allowing full valve lift, or increasing
wear?

I'm not sure I understand the reason for not allowing full valve lift, or increasing
wear?

Well if the lifter has too little pre-load is it possible that the spring cup will compress during the lift cycle which will not follow the true profile of the cam? I think that is what is being suggested.

That's right, too little or no pre-load and you get a fair amount of movement of the piston within the lifter, thus reducing valve lift. This is not desirable, it's just what happens.

Steve

That would also be tough on the clip holding in the piston.

I have been reading David Vizards book and he states that pump up is usually the result of slack in the valve train (onset of float) rather then the lifter causing float. But I also thought that valving could cause the lifter to pump up as well holding the valve open and the resulting loss of power.

That's right, too little or no pre-load and you get a fair amount of movement of the piston within the lifter, thus reducing valve lift. This is not desirable, it's just what happens.

I've never heard of setting pre-load to achieve additional valve lift. The function
of Pre-load is to self adjust and take up slack as the valve train parts wear down.

Once you have correctly figured pushrod length, rocker tip alignment, etc., the
pre-load can be set to maintain a certain amount of correction as parts wear down.

The seat is always slopping around to some degree causing a variance in lift
at the valve. For this reason, I believe high output race motors will use a solid cam.

For peformance setups, modest amounts of pre-load can be set to limit the
travel of the plunger...which is getting closer to the function of a solid lifter.
This is one of the tricks I was shown to get a little more power.

As far as I'm aware, the lifter will pump up if the valve floats and creates clearance
between the cam lobe and valve tip.

The intial pre-load amount will always return.


.

I think all the right info is here, just scattered a bit. Here's my version:
o 'Preload' per the factories is the setting/adjusting of the hydraulic piston in the lifter somewhere near it's mid-travel point, so that it can extend to account for heat expansion or contract to compensate for wear.
o 'Pump up' as the word is normally used by performance enthusiasts, is the lifter doing it's thing and taking up what it sees as 'clearance' but which is actually valve float. Thus, when the cam rotates to the base circle, the valve is still propped open, leaking compression, until the lifter adjusts itself back to normal.
o By setting the preload very small, the lifter seat cannot move far enough to prop the valve open very much, so the power loss at and immediately after valve float is reduced. Clearly this is a band aid. If it's happening regularly, you need better valve gear or less RPM!
o Vizard actually makes another point I hadn't though of, namely that even at the best of times, oil contains a fair bit of very compressible air which, especially with stout springs and high lift, means that as much as 0.020" 'collapse' can occur during a valve event, robbing lift and duration from the nominal cam profile. His solution is to select longer push rods and adjust the lifters within a few thous of bottoming out completely when cold, thus limiting the potential collapse. He says this rarely fails to give a 20 HP gain.
o He also says that in his testing, Royal Purple oil seems less prone to air entrainment and so reduces collapse and adds power in hydraulic cam applications.

Lifter pump up is a function of llifter pre load, valve float, and oil pressure. You are pretty limited on valve spring pressure so valve float is pretty much a given if you push the rpm too high.

In a hydraulic lifter racing engine you adjust the valves for zero preload on a hot engine. That way the lifters can not pump up during valve float and hold the valves open. You need lifters with strong tru arc clips holding the push rod cup and piston in place. Most stock type lifters have cheap bent wire clips.

Street engines can be adjusted with about .010" to .015" preload hot. You obviously need adjustable rocker arms to do this.

As Bill stated, if the oil is aerated the lifters will collapse a bit reducing both lift and duration. Increasing the oil pressure will help. The best solution is dry sumping the engine if you indeed want or need to keep a true hydraulic lifter in the engine.

Stock eliminator racers have another trick. They prop up the push rod cup -piston with a steel pin inside the hydraulic lifter. The pin keeps the lifter from fully collapsing if the oil does get aerated - almost a certainty. Some cam companies sell these lifters but don't advertise them.

By the way, I've built hundreds of hydraulic lifter racing engines through the years.

Steve

I think all the right info is here, just scattered a bit. Here's my version:
o 'Preload' per the factories is the setting/adjusting of the hydraulic piston in the lifter somewhere near it's mid-travel point, so that it can extend to account for heat expansion or contract to compensate for wear.
o 'Pump up' as the word is normally used by performance enthusiasts, is the lifter doing it's thing and taking up what it sees as 'clearance' but which is actually valve float. Thus, when the cam rotates to the base circle, the valve is still propped open, leaking compression, until the lifter adjusts itself back to normal.
o By setting the preload very small, the lifter seat cannot move far enough to prop the valve open very much, so the power loss at and immediately after valve float is reduced. Clearly this is a band aid. If it's happening regularly, you need better valve gear or less RPM!
o Vizard actually makes another point I hadn't though of, namely that even at the best of times, oil contains a fair bit of very compressible air which, especially with stout springs and high lift, means that as much as 0.020" 'collapse' can occur during a valve event, robbing lift and duration from the nominal cam profile. His solution is to select longer push rods and adjust the lifters within a few thous of bottoming out completely when cold, thus limiting the potential collapse. He says this rarely fails to give a 20 HP gain.
o He also says that in his testing, Royal Purple oil seems less prone to air entrainment and so reduces collapse and adds power in hydraulic cam applications.

Excelent thread guys!!!

Good call on the pre-load setting. I'll set mine cold initially, then run
the motor to temp.

Using my dial indicator, I'll re-set the pre-load to 0.005" and then run the
motor. I have been able to get 3HP on the dyno by resetting the valves.
My idle vacuum picks up a few points as well which means it's not only a
high RPM application.

I still don't know of any hydraulic cams in Pro-stock, or similar race classes.
That is what I meant by 'high output race motor'. Sorry, I should have been
more specific.

So, is the aeration problem (which I first heard about on this thread) a reason that 1) LS1's seem to run such high oil pressure, and 2) GM dry sumped the LS7?

Overall, this just raises the question, especially with adjustable rockers needed anyway, that more LS1 engines aren't using solid lifters. Is it rule restriction in the racing classes?

Yes, the ls1 has been said to have a pretty poor oiling system from the standpoint of introducing a lot of air into the oil during high rpm operation. I believe alot of it comes from the undersized pick up of the oil pump and the way the oil just sloshes all over the crank shaft. I think this needs to discussed as a new thread. Anyone else???

Oil sloshing over the crankshaft is a windage and sump problem. Cured in a straight forward, if not easy manner (for that matter, you don't see too many (any) people mention no-hole balance here either). Similarly, it is not rocket science to design a pan that keeps the pickup in the oil.

That should be a separate thread.

Have you looked at the bottom of a LS1 compared to that of a stock SBC? The LS1 has oil control measures everywhere. I'm actually really impressed with the underside of the stock LS1 in terms of oil control.

There are a few things you can do to improve SBC oil pumps to get the aeration of the oil down. Haven't tried to over anaylize a LS1 pump yet so I can't tell you anything about that.

Bret

Guys it's my understanding of the following and if this is way off please tell me. The oil pick up of the oil pump is actually supplied oil by the pressure that is created in the oil pan from blow by and such which drives oil up the pick up tube to the pickup side of the pump and then the pump's gear rotor design distributes it to the rest of the block. Is this correct? It's also my understanding that the gear rotor rotates rather quickly and sometimes the pickup side of the pump can not compete with the dishcharge side and air is introduced by the gear rotor into the oiling system. Any thoughts on this?

Have you looked at the bottom of a LS1 compared to that of a stock SBC? The LS1 has oil control measures everywhere. I'm actually really impressed with the underside of the stock LS1 in terms of oil control.

There are a few things you can do to improve SBC oil pumps to get the aeration of the oil down. Haven't tried to over anaylize a LS1 pump yet so I can't tell you anything about that.

Bret


Doesn't the oil sling onto the cam from the bottom of the lifters via the enormous lifter oil galeys and from the cam to the crank and cause a good amount of aereation though??? Obviously a good bit of the oil recieved from the lifter oil galleys will go up to the top of the motor through the lifter through the pushrod but isn't a good bit doing what I described before. Once again, this is a question, not a suggestion.

The pick up of oil will not be affected by crankcase pressure because it is essentially constant throughout the engine, i.e., the only pressure difference existing to force the oil into the pump is provided by the suction from the gears themselves.

Doesn't the oil sling onto the cam from the bottom of the lifters via the enormous lifter oil galeys and from the cam to the crank and cause a good amount of aereation though??? Obviously a good bit of the oil recieved from the lifter oil galleys will go up to the top of the motor through the lifter through the pushrod but isn't a good bit doing what I described before. Once again, this is a question, not a suggestion.

Oil is picked up from a (hopefully) de-aerated pool of oil in the bottom of the pan or tank. Otherwise you pump air, not a good lubricant.

Suction from the pump picks up the oil. Oil galleries from the pump supply the main bearings and lifters under pressure. Oil passages in the crank supply the rod journals. In high performance applications, oil supplied to the piston pin via pressurized feed through the rod. Cam journals are fed under pressure from the pump. Cam lobes are lubricated from the lifter. Some solid lifters have pressurized feed holes for the lobes. Cylinder walls are lubricated from oil throw off the rod and main journals. The head is lubricated with oil fed through the pushrod.

Oil is typically returned to the sump via gravity. In a dry sump, scavenge section create a vacuum in the sump, and in some installations also in the lifter gallery and/or rocker covers.

Windage trays and scrapers ensure oil is removed from the crankshaft throws. A no-hole balance further keeps oil off the crank. Profiled throws help reject oil quickly. Block preparation focuses on a quick an uneventful return to the sump.

Since these passages are by and large cast into the block, there are frequently many compromises. One big SBC enhancement is to feed oil from the pump directly into the main oil gallery feeding the mains via a port above the water pump.

I believe oil pressure is typically read from a sensor on the oil gallery to the main bearings.

My question was if engine builders did modifications to increase the oil pressure to the lifters, increasing the load they can handle.

Please correct any errors. This is an area where my knowledge is far from complete.

My question was if engine builders did modifications to increase the oil pressure to the lifters, increasing the load they can handle.


I was under this same impression though I have no proof of my own.
At first thought, higher oil pressure still is no match for spring pressure.
I believe the spring force is multiplied by the rocker back to the lifter in that a 1.7 ratio rocker would add 70% to the spring pressure as measured at the lifter. A 300 lb spring would apply 510 lbs at the lifter. I see no way that oil pressure could compete with that. The liquid oil is not supposed to be compressable in any case.
The higher oil pressure may only prevent the existance of air bubbles in the oil which in turn could have benefit in extending the operating range.
This is only a deduction by the way. I have no proof.

Ever try to compress a fluid? ;')

Spring pressure would likely increase the bleed down rate, but once the lifter
is high up in the bore, I don't think the seat is easily swayed downward.

Oil is a imcompressable fluid... that's how it does it. Same way that the bearings can handle the forces of the crank, rods and pistons.... believe me there is much higher loads on the bearings than on the lifters.

AIR IN THE OIL IS REALLY BAD!

Bret

I was under this same impression though I have no proof of my own.
At first thought, higher oil pressure still is no match for spring pressure.
I believe the spring force is multiplied by the rocker back to the lifter in that a 1.7 ratio rocker would add 70% to the spring pressure as measured at the lifter. A 300 lb spring would apply 510 lbs at the lifter. I see no way that oil pressure could compete with that. The liquid oil is not supposed to be compressable in any case.
The higher oil pressure may only prevent the existance of air bubbles in the oil which in turn could have benefit in extending the operating range.
This is only a deduction by the way. I have no proof.

Once the lifter is pressurized, it can only bleed down through a small orfice. Within the lifter it maintains a higher pressure.

Oil is a imcompressable fluid... that's how it does it. Same way that the bearings can handle the forces of the crank, rods and pistons.... believe me there is much higher loads on the bearings than on the lifters.

AIR IN THE OIL IS REALLY BAD!

Bret

It is my understanding that the bearing pressure isn't supported by pump supplied pressure. A 'hydrodynamic wedge' forms that supports the crank.

This article may have some info: http://johnsonsoilpumps.com/perform_frame.htm

The article is explaining why you only need 45psi or so in an SBC to achieve the needed 5 gal/min flow rate. That was another thing I didn't understand, by LS1s run such high oil pressures. Maybe it is those ridculous hydraulic lifters (oops, I let my opinion in.)

Hydo should be your key there..... it works because oil is a incompressable fluid... air is a compressable fluid. That's why a HYDROdynamic wedge works.

The pressure is not the key it's keeping the air out of the oil that's the key.

One more thing... the world works the way it does, it's not our job to tell it how it works, but to figure out how it does. You can think the wrong thing but the world can keep going on and doing what it always does.

Bret

Mad bill brought up the issue of aeration of the oil with this post:

Vizard actually makes another point I hadn't though of, namely that even at the best of times, oil contains a fair bit of very compressible air which, especially with stout springs and high lift, means that as much as 0.020" 'collapse' can occur during a valve event, robbing lift and duration from the nominal cam profile. His solution is to select longer push rods and adjust the lifters within a few thous of bottoming out completely when cold, thus limiting the potential collapse. He says this rarely fails to give a 20 HP gain.
Maybe he could address it further.

If your lifter plunger is only .005" from bottoming out inside the lifter body, then the maximum compression can be no more than .005". This means you would loose no more than a maximum of .0085" lift at the valve with a 1.7 ratio rocker. This would be the case no matter how much spring pressure you are running.
I believe this is one of the sneaky tricks that some racers limited to stock hydraulic lifters use to get 8000+ RPM with a hydraulic setup.

This is kind of the opposite of running with very little preload. If you run only .005" preload, then the maximum pump-up you can get is .005" or .0085" at the valve.

Now that depends if you set it hot or cold. If you set it cold, there would be a bit more than .005" when hot.

I thought this would be a good addition to the discussion.

Copied from Mike at www.chevelles.com

This tech paper will discuss the adjustment of
Chevrolet hydraulic lifters (“valve lash”).

The
procedure outlined here differs slightly from the Service Manual, and is
based on my years of experience doing this work in the quickest, least
painful, most economical way while keeping the level of quality high. It
is recognized that other people will have different methods of doing
things, and may disagree with specific methods and procedures that I
use.

Overview, Theory and my Thoughts on Lash Settings
Hydraulic
lifters are wonderful little innovations which reduce valve train wear and
virtually eliminate required valve train maintenance.

Without the
use of hydraulic lifters (mechanical lifters), the valve train must be
adjusted with a certain amount of “slop” in it
(“lash”). This lash is necessary, since the various
components in the valve train tend to “grow” and expand as
they heat up from normal engine operation. As the components
“grow,” they take up a large portion of the lash, but some
lash must still be retained as a safety margin. If there were no lash,
there would be a risk of the valves not closing fully, resulting in poor
engine performance and burnt valves. This lash, however, results in a bit
of valve train noise as parts “clank” together, and this
clanking induces wear of the valvetrain components. This wear, in turn,
requires that the lash be re-adjusted at regular intervals. If only there
were a way to eliminate the lash…. hmmmmm….

Enter the
hydraulic lifter. Believe it or not, but the internal components of a
hydraulic lifter are the most precise, close-tolerance parts on a vehicle.
The basic operation and principle of the hydraulic lifter is as
follows:

When the hydraulic lifter is at the “low”
point in its bore (the valve is closed), the body of the lifter is
exposed to pressurized oil in the lifter oil galley. The lifter body has
a little hole in it, and this hole allows oil to enter and/or exit the
lifter body. The pressurized oil in the galley thus enters the body of
the lifter, and pushes lightly on a plunger in the roof of the lifter
body. This plunger is about a half inch in diameter, giving it a total
area of approximately 0.12 square inches. If you’re running 60
pounds of oil pressure, that means that the oil is pushing upwards on the
plunger with a force of about 11 pounds max. This 11 pound force is not
enough to open the valve, but it will remove all slack out of the valve
train.

As soon as the lifter starts moving upwards in its bore (the
cam is opening the valve), the oil hole in the lifter body moves out of
alignment with the oil galley. The lifter body is sealed off, and oil
can’t get in or out of the body. The lifter, thus, goes into
“hydraulic lock,” and suddenly acts like a solid lifter. The
oil under the plunger is not compressible, so the lifter now opens the
valve.

As the lifter comes down the bore after completing its valve
opening chore, it is once again exposed to the oil pressure in the lifter
galley, and the pressurized oil once again assures that all lash is taken
out of the valvetrain before repeating the opening cycle. As the
valvetrain wears, the oil pressure simply constantly pushes the plunger
upwards to remove any slack caused by the wear. The plunger can be pushed
upwards in the lifter bore within the design limitations of the lifter,
and will eventually be stopped by a snap ring retainer in the top of the
lifter body. Once the plunger reaches the retainer, it can no longer
provide effective valve train adjustment, and the valvetrain will start
making noise.

The distance the plunger is compressed into the
lifter body when the lifter is at the low point in its bore is referred to
as “lifter preload.” This is the “valve lash” or
“valve adjustment” on a hydraulic lifter. The further the
plunger is depressed, the more wear the lifter can “absorb”
before reaching the snap ring retainer. However, the more the plunger is
depressed, the more prone the engine becomes to “lifter float”
or “valve float.”

As we noted earlier, the oil in the
lifter is not compressible. If, somehow, the lifter body were filled with
just a few drops of oil too many, and the lifter were moving so fast in
its bore that the oil did not have a chance to bleed out and re-stabilize
the valvetrain lash at the bottom of the lifter travel, the lifter would
keep the valve open when the valve should be closed. Further, if
aggravated, this condition could cause the lifter to open the valve beyond
its design limitations, out of time with the intended valve cycle. This
is what is known as “lifter float” or “valve
float.” It can have disastrous consequences if the valve were to
hit the piston. We, therefore, adjust hydraulic lifters with some
pre-load, but not too much. So what’s the right
spec…?

Obviously, we can eliminate valve float completely by
simply adjusting our lifter pre-load such that the plunger is right at the
top of the lifter body; right up against the snap ring retainer. The
problem with this approach is that there is the possibility of the same
hydraulic lock conditions exerting so much force on the snap ring that the
snap ring is forced out. With nothing retaining the plunger, we would
have the same disastrous ending to our engine… Also, with no
plunger travel available, the non-maintenance feature of our hydraulic
valvetrain is defeated, and we must now constantly adjust the valves as if
they were mechanical.

The factory setting on a Chevy lifter
pre-load is ¾ to 1 turn lifter preload with the lifter on the low side of
the cam (valve closed). This eliminates valvetrain maintenance for at
least 100,000 miles, and is a good compromise setting. However, it can
allow the valves to float at rpms as low as 5700. This, effectively,
becomes a factory-installed rev limiter: if they can make the valves float
lightly around 6000 rpm, GM can reduce warranty claims from customers
over-revving their engines. Hey… these boys and girls designing
this stuff in Detroit aren’t dummies, are they?

So for a
performance application, we split the difference. A ½ turn lifter
pre-load will raise the rpm limit of the engine, yet it will still provide
quite a bit of plunger travel so the lifter can do its valvetrain wear
adjustment thing.. It will also keep the plunger away from the snap ring
retainer, and it will keep our operation safe. Safe, reliable, improved
performance and good durability/life: what more could you ask
for?

Continued:

Procedure
This procedure typically takes me about
30 minutes from start to finish on a Chevy without air conditioning, but
I’ve done it a few times. Allow yourself an hour or two for a
leisurely pace of wrenching and beer drinking.

General
tips:
Keep your work area clean and organized. It’ll make the job
seem much easier. I like to lay a clean towel out on the ground by the
car or on an adjacent workbench. As each bolt, screw, nut and component
is removed, I lay the parts out carefully on the towel. Whenever
possible, I put screws back into the holes that they came out of after the
component is removed. Wipe up spills and sweep the area as you progress
to keep things clean and pleasant. You will be leaning across the fenders
on pre-C4 cars, so use a fender apron.


Step-by-Step:
·
Park the car on a level surface. Set the parking brake and block the
tires. On manual cars, put the trans in neutral. Pull the coil wire that
goes from the distributor cap to the ignition coil (on HEI cars,
disconnect the connector out of the distributor) and ground it.
·
Turn the engine over until you can see the timing mark on the harmonic
balancer. Using a piece of chalk or other visible marker, place three
more timing marks on the balancer: one mark every 90 degrees around the
balancer (one exactly opposite the factory mark, and two in between these
marks: just get it pretty darned eye-ball close, it doesn’t have to
be exact.)
· Remove the valve covers. You may have to remove some
accessory brackets in order to do this.
· Rotate the engine over
(either by “bumping” the starter or by inserting a socket and
breaker bar onto the harmonic balancer bolt) until the factory timing mark
lines up with “0.” Observe the pushrod for the exhaust valve
on the #1 cylinder: if the pushrod moves as you come up on Top Dead
Center, you’re on the exhaust stroke, and you need to rotate the
crank one more time. If neither pushrod moves as you come up on the
timing mark, you’re on the compression stroke and ready to go.
·
Loosen the adjustment nuts on both the rocker arms for cylinder #1 using a
deep socket and a ½” drive ratchet. One at a time, adjust them as
follows:
· Place the pushrod between you thumb and forefinger of your
left hand (or right hand if you’re left handed…). Rotate, or
“twirl,” the pushrod back and forth between your fingers and
notice how lightly and easily it spins. As you do this, slowly tighten the
rocker arm nut. The instant you feel the “twirl” friction
change between your fingers, you are at “0” lash. STOP. Now,
notice the position of your ratchet handle. Tighten the nut exactly ½
turn from your current position. Do the same to the other rocker arm for
#1 (when doing this, make sure that the friction you feel as you swirl the
pushrod is not caused by your ratchet and socket pushing or binding on the
rocker arm – keep things straight and aligned, and watch for false
indications caused by your tools). That’s it for #1.
·
Now, here’s the trick:
What’s the firing order for a GM
V8?
1-8-4-3-6-5-7-2
How often does a cylinder fire in a V8?
Every
90 degrees
That means we can now rotate the crankshaft 90 degrees at a
time, and go right to the next cylinder in the firing order for the valve
adjustment, with confidence that both of the valves for that cylinder will
be closed and ready to adjust.. So rotate to your next chalk line, and
adjust #8 as described above. Rotate to the next line and adjust #4.
After you’ve rotated the crankshaft twice over (using the starter
and “bumping” is the easiest way), you’ve finished your
valve adjustment! No oily mess, no worrying about if you missed a valve.
Just a nice, simple, structured procedure!
· Pop your valve covers back
on with a fresh set of gaskets, re-install any accessory brackets
you’ve removed, and start it up with confidence. You now have a
correctly adjusted valvetrain that will operate quietly and with
outstanding performance and reliability.:
__________________
Mike
TC#355
aces member #03260
69SS396
69 convertible
68 convertible
72 Olds 442 convertible
http://www.chevelles.com/showroom/69SSRat/chevelle.jpg

Anybody know how much plunger travel is in the lifter from min to max?

Mad bill brought up the issue of aeration of the oil with this post:


Maybe he could address it further.

I'd do better if I could find the recent Popular Hot Rodding (I think it was) that had the Vizard article, but basically he said that at the best of times, there's a significant percentage of air entrained in the oil (Smokey Yunick said it takes hours to dissipate after an engine is shut down and that much of it is bubbles so fine the oil just looks a little murky) and that with normal lifter adjustment, depending on spring force and RPM-induced inertia loads, there will always be 0.010" or more loss of lift and some degrees of closing side duration compared to the actual lobe profile. He details a procedure (he doesn't say, but I would think it applies to iron block SBCs) to set the preload only around 0.005" shy of bottoming out with the engine hot, to limit the potential collapse.
He also mentions that modern aggressive hydraulic roller profiles exert quite high side loads (high pressure angles) and that several brands of lifters were found to distort and haemorrhage oil under load, thus often collapsing a further 0.020" or more.
Additional points he made included that Royal Purple was the best oil he had found for minimizing air entrainment and that Morel was initially the only roller lifter with sufficient rigidity to avoid distortion-induced leakage, but that Crane, CC and others had now improved their products to match.

A couple of points of my own:
o Per a question above, I believe typical hydraulic lifters have ~1/8" travel.
o It's actually the volume of oil contained, not the available lifter 'down' travel, that determines potential for collapse, so a near-bottomed out lifter with an appropriately longer pushrod should have less collapse than one with a travel-limiting spacer. (unless the spacer is large enough diameter to displace almost all the oil)*
o Adjusting lifters to near bottomed out is a balancing act: Are we sure we know when component thermal expansion/contraction will result in minimum lifter seat travel, especially with aluminum blocks? Who wants to burn a few valves finding out?**
o In Mike's well-detailed write up above, if the oil pressure exerts only 11 lb. max. force on the lifter seat, how can it beat out the circlip? Although the internal pressure rises much higher during lift, the pressure is due to force transmitted by the pushrod, and so will hold the seat down.
o *Maybe there's a new product opportunity here: Minimize the volume of oil in the lifter and you minimize the potential loss lift due to compressing the oil/air mixture that passes for lubrication in an engine!
o **Case in point: A well-know West Coast Porsche tuning/race shop was checking the effect of valve lash on engine power. Output kept improving with tighter lash until they broke for lunch. When they came back, the engine wouldn't start. The valve lash had closed into negative territory as the air-cooled all-aluminum mill dropped to ambient temperature...
o When you try to rev your Mom's '56 Dodge station wagon to 60 MPH in first gear, it pumps up the lifters at 57 MPH and the engine won't re-start for almost an hour. (Don't ask me how I know this...)

Now that depends if you set it hot or cold. If you set it cold, there would be a bit more than .005" when hot.


I'm not sure I understand this??? If you set .005" cold and when the block expands there will actually be lash in the system more then likely, therefore no pump up would occur. Ofcourse, other problems will arise then. It's been said that the ls blocks expand roughly .010" when warm.

Edit: Are you suggesting the valve train components expand more so then the aluminum block and heads do???

Net, net, net...is this all a case for solid lifters in a modified engine?

I'm not sure I understand this??? If you set .005" cold and when the block expands there will actually be lash in the system more then likely, therefore no pump up would occur. Ofcourse, other problems will arise then. It's been said that the ls blocks expand roughly .010" when warm.

Edit: Are you suggesting the valve train components expand more so then the aluminum block and heads do???

That was .005" of the bottom not the top. The discussion was about limiting compression in the lifter. It would expand with the block expansion when hot, because, as you said, the block expansion is greater.

Net, net, net...is this all a case for solid lifters in a modified engine?

Sorry, i'm rather slow at times. Could you please elaborate??? Thanks.

edit: Nevermind, see above. The confusion was generated from the gentlemen above you speaking of .005" pre-load, not .005" from bottoming out. I got it now:)

As I mentioned, there are a lot of variables. For example, what if the car has a great cooling system and say a 170 thermostat, but is being track raced with an inadequate oil cooler. The oil in the sump reaches 275 F. but as is known, may well be 25 higher internally. This means the lifters and push rods are running 130 degrees hotter than the block and expanding proportionally...

And yes, I think there's a great case for solids: More power and RPM potential, even with similar lobes, tons of lobe families to choose from (I think CC alone has probably 20 or more, with dozens of lobes in each) and they don't need attention all that often unless you go pretty radical on the profile and use the top end of the tach often. (My factory solids '70 Z28 would go for many thousands of mile without adjustment, but the rocker arm 'lock' nuts would back off any time I ran it over 6,000, until I switched to aftermarket ones) And if you do drive it hard all the time, you should be checking things regularly anyway. Running the lash is a fine opportunity to look around...

Guys it's my understanding of the following and if this is way off please tell me. The oil pick up of the oil pump is actually supplied oil by the pressure that is created in the oil pan from blow by and such which drives oil up the pick up tube to the pickup side of the pump and then the pump's gear rotor design distributes it to the rest of the block. Is this correct? It's also my understanding that the gear rotor rotates rather quickly and sometimes the pickup side of the pump can not compete with the dishcharge side and air is introduced by the gear rotor into the oiling system. Any thoughts on this?

Yes as the oil pump spins and creates a void with lower pressure, the air in the crank case is pushed up the oil pump pickup tube and into the pump's low pressure inlet side of the housing. At best the pump could drop the inlet pressure down to absolute zero PS1 so the true pressure differential existing between this low pressure side is directly dependent on the oil pan pressure. This is also why you start seeing rods flying often when peoiple run a lot of vacuum on wet sump engines as well.

I'm not sure I understand the reason for not allowing full valve lift, or increasing
wear?


I love your sig, yeah everyone is a mechanic here with a 10 second car.

I love "Z"'s signature too.
It looks like we race books, not cars in this section.

Rich

As I mentioned, there are a lot of variables. For example, what if the car has a great cooling system and say a 170 thermostat, but is being track raced with an inadequate oil cooler. The oil in the sump reaches 275 F. but as is known, may well be 25 higher internally. This means the lifters and push rods are running 130 degrees hotter than the block and expanding proportionally...

And yes, I think there's a great case for solids: More power and RPM potential, even with similar lobes, tons of lobe families to choose from (I think CC alone has probably 20 or more, with dozens of lobes in each) and they don't need attention all that often unless you go pretty radical on the profile and use the top end of the tach often. (My factory solids '70 Z28 would go for many thousands of mile without adjustment, but the rocker arm 'lock' nuts would back off any time I ran it over 6,000, until I switched to aftermarket ones) And if you do drive it hard all the time, you should be checking things regularly anyway. Running the lash is a fine opportunity to look around...
So why isn't every one here running solids?

Well, I now have an aluminum 495 big block in the Camaro, with the factory ZL-1 solid flat tappet cam (Trivia question: What engine has the highest lift cam ever factory installed in a GM production vehicle? Hint: It's not the LS7...), soon to be replaced by a custom solid roller, and my last two daily drivers ('87 Metro and '03 Vibe) both were factory-fitted with solids, so I'm doing my part! :burn:

I'd conisder a solid cam for a weekend driver. Valve cover access on my second
gen is a snap.

I don't think most people are prepared to spend the coin to properly fit a solid
cam and valvetrain in a daily driver. I doubt they'd want to check lash every
other week on top of that.

A friend of mine runs Top Sportsman and he will check/adjust the valves after
every pass. It's a high maintenance setup, I think that's the main reason most
shy away.

I'd conisder a solid cam for a weekend driver. Valve cover access on my second
gen is a snap.

I don't think most people are prepared to spend the coin to properly fit a solid
cam and valvetrain in a daily driver. I doubt they'd want to check lash every
other week on top of that.

A friend of mine runs Top Sportsman and he will check/adjust the valves after
every pass. It's a high maintenance setup, I think that's the main reason most
shy away.

There is a thread elsewhere on LS1Tech where people discuss how much they spent. Doesn't sound like $$$ are the issue. If using an AFR, ET, Dart, or World head, the cost is set of shaft rockers.

Your friend is probably a great racer, but not the last word on valvetrain maintenance. They have been used extensively before the latest phase of emissions laws. For example, my Supra TT's direct action valve train is solid.

Actually my friend isn't all that good at bringing home the win, but that's Ok.
I wont say he's god when it comes to motors, but he's pretty good at what
he does. Checking valves after every pass might seem overkill, but when
you're spinning a motor to 8000 RPM rods can bend, and things come loose.
It's a sanity check if nothing else and could save the top end from damage.

I'd say people will shy away from solid cams due to maintenance over costs,
and possibly the justification of actually needing a solid setup.

As for the mechanical considerations, I wouldn't stop at rockers alone.
Depending on the lobe profile springs might need to be changed, harder rods,
maybe stronger studs or a girdle. Maybe costs are an issue for some at that
point. Who knows. Just sharing some info.

Shaft rockers don't need girdles and replace the studs with bolts.

Yes, the adjustable shaft rockers would be a nice upgrade for high RPM stability.

I installed my stock rockers on my 408,afr headed motor,with 7.4 pushrods.I tighten the rocker to zero lash and then turned it 1 full turn then it got tight,am I good as far valve lash is concerned?

I'm sure you'll be fine for the most part, but it's tough to gauge the seat
depth using the 'wrench turn method'.

I think it's a little too much when comparing the wrench angle for 0.005-0.020"
on a standard thread stud. For example, 0.005" is about 1/8th turn of the
wrench.

With a roller cam, you don't need much pre-load at all. You will pick up some
RPM and power with a well adjusted valvetrain.