1993 Yukon crate motor hydraulic roller lifter cleaning and adjustment journey - (Solved)

[Road Trip]

Just watched your video. Big picture, the engine really seems to be running smoothly.

Since this is the hardest thing to achieve, I don't think that you need to second-guess
your work. To me, a smooth idling engine means that the valves are seating properly.
And this is of key importance, because the only time that the sealing surface of the exhaust
valve gets to cool off is when the valve is firmly seated and conducting heat into the
surrounding water jacket.

In English, you have maximized your Reliability, so most of the pressure is off. But
of course our very next challenge is to figure out are the remaining noise(s) a warning
of trouble down the road? Or is it a minor nuisance that the current assembly of parts
will continue to generate no problem for the next 5+ years?

Given this, next in importance to us is how quiet this smooth-running engine is. There
are a *lot* of variables here, since oil pressure varies all over the place. (For example,
@Keeper in reply #89 has a valid point, especially if air got temporarily sucked into the
system due to where the oil pump pickup is vs where your oil in your sump was situated
due to the way you parked?)

I know that I fear most what I understand least. And when I listen to something, I want to
be able to figure out which sounds are normal/forgettable for a specific design, and which
sounds are abnormal and next to be addressed without delay?

****

In the next 2-3 replies, I am going to do my best to give a big picture overview of the
various sounds in a adjustable hydraulic lifter valvetrain. Whether or not disturbing
the valvetrain in a long-running engine has put us afoul of internal varnish deposits or
other issues can't really be decided until the following info is read for comprehension.

 

[scott2093]

Thanks. I just started the truck since this morning. Was sitting level in road for I guess a few hours...It tapped 3 or 4 times and went away...... if that's a clue... kinda how it's been going though. Seems like next morning starts are where the action is

 

[Road Trip]

Hydraulic Lifter noise - Part I -- Does it pass visual inspection?

Hydraulic lifters are both the highest precision and highest stressed parts inside
the Chevrolet pushrod V6 & V8 motors. Without the precision fitting between
the internal plunger and the lifter body the lifter won't 'pump up' and act like a
solid lifter while riding the cam lobe from the base circle to the lobe peak.

And with pressures ranging between 200,000 & 300,000 PSI between the lifter
base and the cam lobe, if everything isn't right, even brand new parts can fail
in the first few minutes of operation after a rebuild. (!)

One more thing to consider. Back when your truck was being manufactured,
the Big Three were ordering *millions* of full sets of flat tappet hydraulic lifters
in order to help keep those vehicles popping off the assembly line one a minute.
And those of us building engines back in '93 had more OEM-quality lifters to choose from
than we knew what to do with. (!)

But here in 2024 new car manufacturers are no longer buying flat-tappet hydraulic
lifters in any kind of volume. Companies went out of business. Production of these
precision assemblies was sent offshore. Instead of the people involved having 30+
years of experience, you now have people with 30 weeks of experience trying to make
very precise things at a very low price point. It has been a race to the bottom, and
even very talented engine builders were being bitten by the confluence of lower quality &
higher spring pressures, and had thrown up their hands, and moved to only roller-lifter
builds.

The more you dig into all this, the more you find that finding a
OEM quality flat-tappet lifter is about as easy as finding top quality vacuum tubes
for your highly resolving audio system in your listening room. :0)

So once upon a time folks would tell you that if you had any noise in your valvetrain
just replace it all with good, affordable fresh bits. But we no longer have that luxury,
so in order to make the best of what we have to work with, we need to understand
the valvetrain more than we used to. Not as much as the designers, but at least enough
to be an informed consumer or careful troubleshooter.

****

There are 2 distinct categories of lifter noise:

* Physical exterior deformation/failures that create extra clearances/sudden audible shock forces.

* No exterior physical wear, but excess play due to installation misadjustment or out of tolerance
internal clearances. (!)

****

To make this short enough to actually be read, I am going to rely mostly
on photos & links to relevant articles.

In order to appreciate all the hidden engineering on the flat tappet hydraulic lifter,
here's a diagram explaining how a new one is actually shaped:

You must be registered for see images attach

NOTE: Illustration is exaggerated for visualization. Actual radius is subtle -- visualize the base of the lifter as part of a large wheel with a radius of ~35". (!)
Also note that the top of the cam lobe is cut with a slight angle to encourage rotation -- this is what spreads the load/wear evenly. This lifter spinning
helps to provide a constant freshly lubricated lifter base to the cam lobe. A non-spinning flat tappet (hydraulic or solid) will lead to rapid wear.

Even though subtle, 2 new lifters placed end-to-end will wobble slightly instead of sitting straight up.


Here are 4 different wear modes as shown in a late '50s Buick shop manual:

You must be registered for see images attach

(credit: hometownbuick.com: LINK)

Upper left used lifter with acceptable wear - reusable, but only with the exact cam lobe it came from.
The 3 other lifters show typical failure modes, and must be scrapped.

****

Here's a photo of an actual failed cam & lifters:

You must be registered for see images attach

Delphi lifter with hardened base ("B") is regarded as one of the best choices available today:

You must be registered for see images attach

(credit: Motor Trend / Car Craft article on flat tappet lifter reliability: ARTICLE)


And here's another failure to take a look at, courtesy of @PlayingWithTBI: (5,000 mile cam failure)

****

To summarize, there are 2 primary sources of noise. If the sound cannot be fixed via adjustment,
then the next step is to perform a careful visual inspection.

 

[Road Trip]

Hydraulic Lifter Noise - Part II - Theory of Operation / Reliance on a Steady Oil Supply

In order to understand how oil flows inside your lifter, here's a pic from an animation
showing how it operates:

You must be registered for see images attach

NOTE: This is a slightly different physical implementation, but the spring-loaded ball operation is the focus. (Watch it over here: Hydraulic Lifter Animation)

Now I've found that in order to find the best technical explanations of any given technology, the best
ones are from the time that the technology was introduced. Here's an old school hydraulic lifter training
slideshow from 1954 by Chrysler. Seems that a lot of these new lifters were being replaced by dealer mechanics
on cars under warranty due to excess noise, and the company was trying to help them understand that too
much or too little oil could adversely affect this new technology that relied on engine oil that was not aerated:

xc_hide_links_from_guests_guests_error_hide_media

Training was a lot different 70 years ago. The trainer would play a record
and then change the slide every time there was a beep. But the actual
content of the training was actually pretty high quality. Enough theory to
help their mechanics to better troubleshoot these new-fangled hydraulic lifters
instead of just replacing them blindly. Goofy delivery maybe, but good stuff
that's easy to remember.

The bottom line is that clean, unaerated oil is key to keeping our lifters as
quiet as possible.

 

[Road Trip]

Hydraulic Lifter Noise - Part III - How to Quantify Leak Down Rate (FSM)

Back in the '50s, hydraulic lifters were new technology, difficult to manufacture to such
precise tolerances (so tight that it's documented that the assembly was performed by
skilled workers using the 'select fit' method) ...and expensive enough that it was considered a
good business practice to have the dealership mechanics be able to clean and then test hydraulic
lifters for proper operation.

In the '51 Buick Service Manual (had the best photos I could find) here's test fixture
J-5095, showing a lifter being tested in a precise mixture of 12 oz of SAE 10W engine oil
added to 116oz of kerosene, for a gallon of test fluid:

You must be registered for see images attach

(credit: read the whole procedure on hometownbuick.com: LINK)

Check out that stopwatch. With the correct test fluid, the test stand with a calibrated weight, after
cleaning the hydraulic lifter and purging all the air the goal was to have the lifter bleed down between
"9 and 38" seconds. And if the lifter was any kind of flaky, you were supposed to retest it 3 or 4 times,
and it still didn't fall into the window, replace it. Wow.

NOTE: By 1959 they had added a nifty cleaning station, recommended a "Hydraulic Lifter Test Solution"
sourced from Kent-Moore, and changed the time goal specification to "12 to 40" seconds. LINK

Now to tie the detailed test description from the '50s to the GMT400 repair manuals 40+ years later. I found
the briefest description of testing hydraulic lifters tucked away in the '94 GM Light Duty Truck Unit Repair Manual:

You must be registered for see images attach

****

My goal in pulling together this info about how the GM Service Manuals went about quantifying how
long a healthy hydraulic lifter will take to leak down using calibrated test fluid is not to talk anyone
into buying a test setup like this. Or become a 21st-century hydraulic flat tappet engineer.

Instead, when you read the 2 attached 'lifter noise diagnostic charts', my goal is for anyone
reading this (including @scott2093) to be able to follow the fact that some lifter noise can be cured
via external adjustment. (that we've discussed in detail)

But there is a category of noise that can remain due to internal lifter issues, which is why maybe
back in the day one or two of the older mechanics in a dealership service department might check
the leakdown rate on one or more hydraulic lifters in a car under warranty.

And when you read the 2 Lifter Noise diagnosis attachments, please note that if the lifter noise
is only on startup & goes away, the manual claims that there is 'no issue', and no repair required. (!)

****

I was going to go into all the trouble that experienced engine builders have had with flat tappet
engine builds over the past few years, but this would be rehash for anyone still reading this. But
since I can troubleshoot to one or more lifters that are sticky/noisy due to varnish buildup,
AND I can't just throw a new lifter onto an old cam lobe without suffering sure failure...then
I find myself in a 'Back to the Future' moment, where if I was fixing a GMT400 motor with sticky
lifters, I would end up taking each one apart, one at a time, cleaning it, putting it all back together,
and then hopefully @Schurkey would loan me his calibrated hydraulic lifter leakdown tester so that
I could *prove* that when the lifters go back in they are good to go.

One last thing. Ticky lifters are discussed a *lot* by the LS motor guys. Interestingly, not only
does the LS motors share the same 4.400" cylinder bore spacing as the 1st-Gen SBC, they also
happen to share the same lifter diameter: 0.842". And there are those who actually run the
current LS7 lifters in roller-equipped GMT400-era SBCs. So after spending so much time in the
past, here's a glimpse of what I'm considering running in a 383ci SBC that we originally pulled from
a upstate NY Treasure Yard '97 pickup: LS7 Lifters

****

That's pretty much all I have to say about that. Bad hydraulic lifters tick all the time.
Even good hydraulic lifters can tick if you get a little air in them. Or if your loosest
lifter (of 16) wins the engine stop lottery and sits on the nose of it's cam lobe while
you jet away for a holiday in New Zealand. :0)

Hope the past 3 replies was helpful to anyone who's ever chasing hydraulic lifter noise
in their pushrod GMT400 vehicles.

Cheers --

 

[scott2093]

If the sound cannot be fixed via adjustment

I'm reading about my symptoms (tap cold) possibly being a sign of not enough preload?...reduce the air ingestion of the lifter is to lash it tighter...etc......and that it doesn't matter....of course...

I think I'll pull the covers and find #1 tdc just to see what things feel like there........then 180* and see what things feel like??
Don't really want to pull any plug wires if I can avoid it....
Would I get any useful info from checking this way? Like would stuff feel too loose?etc..or because I'm already 1/2 turn, nothing will be too loose? and this is an exercise in futility?

 

[AlaskaBill7591]

I respectfully disagree, because if all the valves were cracked off the seat this would
prevent the engine from starting up, much less a smooth idle.

When adjusting a hydraulic lifter, when you first adjust for no clacking,
you are now at the *top* of the hydraulic adjustment travel that the
inner plunger has to work with. And on the GM engine assembly line
(using factory lifters featuring factory machining & tolerances) they are
supposedly set at 1 full turn, putting the plunger midway in the travel.
(ie: OEM lifters have 2 full turns worth of adjustment available.)

The problem that I and others have run into is that aftermarket hydraulic lifters
will sometimes bottom out with only 3/4 of a turn preload. This is one of those
times when I deviate from the FSM because things have changed with what
gets delivered to the doorstep for me to use while trying to keep these engines
running in the 24+ years since the General originally put ink to paper.

So that's the short version of why I recommend that all 16 lifters are set to just quiet,
and then afterwards a 1/4-1/2 turn of preload is added to the 'just quiet' adjustment point.
I've done this for years & years, and it's the only way I've found that puts a long
term fix on a SBC hydraulic lifter adjustment.

You must be registered for see images attach

For what's it worth, I used to set the hydraulic lifter preload cold,
twirling the pushrods feeling for resistance while at the same time watching
for the lifter internals to just come off the lock ring. After making sure
that the lifters were pumped up prior to placing them in the bores.
And when you used to get all 16 lifters with the same leakdown rates,
they would all act the same and even I could get it pretty close to right
using the prescribed method.

But now when you purchase 16 hydraulic lifters and pump them all up,
then most of them will act the same, but in some the plunger can be
depressed much easier than the others, (due to looser internal mfg clearances)
...and this is why it's so hard for me to do these by feel anymore.

Given all this, my #1 preference is setting the lash on solid lifters. So
much simpler, so many less variables.

My #2 preference is to set the hydraulic lifters with a running preload
adjustment after a best-effort cold adjustment during assembly.

And the rest of the methods? Well, I just don't do it anymore. Instead, I
just excuse myself and resume my spot on the bench. But if asked I'll
jump back in later if the engine is clattery (too loose) and/or exhibits a
rough idle. (Too tight.)

This is just one more data point to add to the mix. No doubt that there are others
who can deliver the same/even better hydraulic valvetrain adjustment using the
cold preload method. Maybe if they can share their process then I can do it too.
No doubt less messy to boot. :0)

Cheers --

PS: Here's a good article from Chevyhardcore about lifter state of the art. Will cure insomnia: (Detailed Lifter Tour de Force)

Sounds to like you already know what you are doing. You are just going to have to verify what changed. Unlike the gasoline engine I don’t think a small intake manifold leak on a diesel affects the running of the engine at idle, plenty of air and stoichiometric ratio not an issue. Do you have any vacuum users to consider, EGR, MAP sensor, or disturbed coolant temp connector for computer, etc.

I’m sure you’ll find it, let us know what you find!

 

[scott2093]

domo arigato.....

So I ran through the passenger side...they were all still half turn...Wanted to make sure I didn't forget one or something....
Tightened another 1/4 turn on them and did the same with driver's side... a few were a bit off from 1/2 turn so glad I caught that....

Truck felt like it idled better with half turn...maybe I'm imagining...
Didn't hear tapping at startup but truck is warm... I need to go listen to how everything sounds but I already put a hose in the pcv hole on passenger side cover after I put it on and could hear louder tapping than I'd like... sucks...



Wonder if I'll be stuck with noisy all the time vs noisy at startup....
going to play some more before it gets too late here....may take an 1/8 off everything...idk...

left the brake booster line off by accident and boy that woke up the lifters...that oil was trying to break long jump records... I'm tired of fighting driver valve cover with booster line at tbi...so much easier without it...

 

[scott2093]

Ate some dinner and went back out and started truck....5 taps from passenger side... Something tells me it'll be worse in morning.... Not sure.. This minor few taps at startup happened several times after my initial intake gasket replacement and lash adjustments and left for oot. So I know it's related to whatever I've done...Hopefully when I set preload cold and it was too tight, I didn't goof something. It ran pretty rough til I decided to hot adjust with running..But I didn't drive the truck...Just idled for a few minutes...maybe a couple or few light revs...

I noticed just now a miss feeling when holding the rpms to 1k...Not liking where it is now.. And idles lower.. doesn't feel tight....

. Looks like I'm going to loosen the rocker nut I'll try an 1/8 and see what it feels like...Already know I'm going to be dealing with cold start tapping....
It's pretty ridiculous sounding... when I started truck to pull in garage earlier , it was way too loud...for way too long....crazy...

 

[tayto]

what oil filter are you running? what weight oil?