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

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scott2093

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So I got some valve covers and cut them up. Have them installed so I can adjust the valves.
So the first one I started loosening started clacking but then quieted down by the time I got to switch the wrench direction. Loosened again, clacked ..same thing. It quieted down.....,tried again, same thing. I just shut it down because I'm not sure if this is normal.?
This is with taking the socket off every time. Truck at full operating temp.... There's really good oil flow so I'm worried it's quieting down from that and I'm not listening right?

Obviously don't want to remove the rocker nut..
Any advice??
Thanks!

edit...I think I got it...Just took a little more loosening.... kinda hard to tell if I'm listening to lifter noise or clacking at some point when I'm tightening but I will see.....
 
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Road Trip

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So I got some valve covers and cut them up. Have them installed so I can adjust the valves.
So the first one I started loosening started clacking but then quieted down by the time I got to switch the wrench direction. Loosened again, clacked ..same thing. It quieted down.....,tried again, same thing. I just shut it down because I'm not sure if this is normal.?
This is with taking the socket off every time. Truck at full operating temp.... There's really good oil flow so I'm worried it's quieting down from that and I'm not listening right?

Obviously don't want to remove the rocker nut..
Any advice??
Thanks!

NOTE: Answer to your question at bottom. What you described makes sense to me,
just have to define some mechanical relationships so that we can discuss why this is happening.


****

Hmmm. I think I know what's going on, but this is one of those things that
will be a bit hard to describe with the written word, so bear with me. Note: This
is also a little bit tricky to pick up the first time or two that you try it, but if you
persevere then this is a very, very powerful diagnostic for sorting out exactly what's
going on with a pushrod engine with individually adjustable hydraulic lifters.

Before I go any further, you may uncover valuable adjustment/misadjustment data
that can be used later on for misfire troubleshooting/resolution. So I need you to
have a pen and paper handy to write down how much you had to back off each individual
rocker arm before it started clacking...and stayed clacking. More in a minute. (!)

****

Converting degrees of fastener rotation = thousandths of an inch upward or downward adjustment.

1) In order to be able to reason through the lifter preload adjustment, we need to translate
horizontal wrench movement into vertical adjustment. In order to do this,
we need to find out exactly how many threads the rocker arm studs and locknuts
have been machined for per inch.

EDIT: In reply #44 below Schurkey correctly pointed out that I was using the rocker arm
ball as the fulcrum in my example, but in reality just as soon as the rocker arm touches
the valve tip then *that* is the fulcrum, and I must now include the 1.5:1 rocker arm ratio to
calculate my vertical adjustment. Tip of the hat to Schurkey - I got it close, he got it right. :0)


Looking up the specs, the SBC rocker arm studs are 3/8" fine thread. Or 3/8" x 24 threads/inch.
Mr. Calculator tells me that 1" divided by 24 = .0416666" per thread. In order to make the rest
of this conversation easier (and also easier to document in the engine bay) let's just call it ~.040" .060"
("Sixty Thousanths") per full turn, and ~.010" .015" per quarter turn.

2) Now let's discuss what we are trying to do via careful listening. The way I understand it,
we have 3 distinct areas of adjustment for the SBC rocker arms. From too loose to too tight,
this is how it will sound:

* Too loose = constant clacking. There is excess play in the entire moving assembly from
cam lobe > lifter > pushrod > rocker arm > valve tip. From constant clacking, we should be
able to transition into just quiet. No excess play in the system, but at the same time no
net preload into the hydraulic lifter.

* Preload window. Using the OEM lifter, the total preload window for the inner adjustment
mechanism (from just quiet at the top to fully bottomed out) is 2 full turns. (Or ~.080" .120")
The factory setting is documented to be 1 full turn, which of course is ~.040" .060" in. This is
so that as normal wear occurs (either slightly shorter as the valve seats recess upward or longer
as the cam lobe wears downward) the hydraulic lifter can compensate for these changing
measurements and keep things quiet during the normal service life...or at least through the warranty
period. (!)

* Too tight = lifter bottomed out, and rough running. NOTE: Way too tight is a solid miss due
to the associated valve being held open/off the seat. Hung open intake can lead to backfire out of the
throttle. Hung open exhaust can lead to backfire out the tailpipe. Both hung open = ?

NOTE: There is a *lot* of discussion about how much hydraulic lifter preload should be run. And
the reason for this is that experienced mechanics following the FSM have set aftermarket lifters
to the "1 turn preload" cold setting, and then had starting or misfire issues afterwards, which
could only be cleared up with a 'running preload' resetting of the valves?

As discussed elsewhere, aftermarket lifters were machined so that they only had a total of ~3/4
turn from the top (just quiet) to the internals being bottomed out.

So now, based on hard-won experience, you will hear the following recommendations:
(All from zero play {cold} or just quiet {running})

* 1/4 turn (~.010" .015" preload) ; works for everything
* 1/2 turn (~.020" .030" preload) ; works for everything
* 3/4 turn (~.030" .045" preload) ; OEM lifters
* 1 turn (~.040" .060" preload) ; OEM lifters per FSM

Personally, I use the 1/4" preload. Why? Back in the day, if I got a little too enthusiastic with
the go pedal (and no rev limiter) then not if but when I floated the valves and the lifters
took up the extra momentary clearance, then I only allowed them to 'pump up'
an extra ~.010" .015", which meant that they recovered quicker than if I had them set to the
full ~.040" .060" from the full turn of preload.)

The second reason is why I do it today. If I build a motor, set everything running to a quarter
turn, and then a year later one lifter starts clacking, then this tells me that there is now a ~.010" .015"
worth of wear I need to investigate? (Or hopefully I just find a loose locknut that needs replacement.)

****

Finally, let's answer your question.

From your description, it sounds like you are loosening the adjusting nut until the lifter starts
clacking. Sounds like you are at the zero-lash point, right? But what's happening is that it
because of the tight clearances, the hydraulic internals take a few seconds to readust to the
new effective length of the entire assembly, and then it goes quiet again. This is expected
behavior, especially if the lifter got set pretty deep into it's preload window.

The solution? Loosen until just clacking Wait a few seconds? Went quiet again? Loosen
a bit more. Wait. Repeat until you loosen the lifter, and it stays clacking steadily. NOW when
you tighten this valve until it is just quiet, you will reach the 'zero lash/zero preload' point.

At this point you have now regained control over the true adjustment of this valve.

Helpful hints while doing this:

* Have pen & paper. Write down exactly what it took to adjust each valve to the zero position.

* Work 1/4 turn (90° swing) at a time. This allows you to quantify all this in .010" .015" increments
if you wish, or want to talk to a machinist, camshaft support hotline, etc.

Example:

#1 exhaust: (3) 1/4 turns (~.045") ; no change in engine
#1 intake: (2) 1/4 turns (~.030") ; no change in engine
#3 intake: (6) 1/4 turns (~.090") ; engine smoothed out after adj. (!)
#3 exhaust: (2) turns (~.030") ; no change in engine
(and so on through the remaining 12 valve settings...)

****

The whole reason for going through this exercise is simply to find the
magic 'zero lash/zero preload' spot for all 16 lifters. Then if you set
the lash for 1/4 to 1/2 turn additional (I do this after finding the
'just quiet' spot sequentially on all 16 lifters, shutting down the
engine, and then setting the desired preload for all.)

If life is good, once you fire up the engine after all 16 have been
preloaded, it should be perfectly quiet. (No bent pushrods, no
carboned up sticky valve stems in guides, etc)

And if you set the preload to 1/4 turn, then as long we don't lose
more than .015" of lifter base/cam lobe to wear, then the valves
will stay quiet for a good, long, time.

Hope this made sense. Good on you for pursuing this. Once you
get all the way through this adjustment I'd really like to see what
you uncovered with your SBC "running preload" (old mechanics 'hot lash')
adjustment.

Quiet valvetrain / smooth running engine vibes in your general direction. :0)

Cheers --
 
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scott2093

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Thanks!
You were probably responding when I was still going at it and was able to get constant clacking. Surely I didn't do it right the first time a couple of weeks ago because I remember it being a quicker process and I'm assuming it is because the preload must have been close if not at fsm spec..Not sure...hmm

The thing that has me confused is the quiet part. Just when it becomes quiet?
I tried having my wife hold a hose to my ear while listening and it's hard to distinguish where to stop as opposed to what I can hear myself standing over the motor with all the noise pollution. It's pretty clear when the clacking stops but, listening real close, you can hear more ticking...Not clacking....

I ended up ditching the hose method and just doing it by ear and 1/4 turn..
I'd really like to dial it in as best I can while it's open obviously... Just not sure When I'm supposed to define the stop point of quiet enough....
The video you linked earlier, he seemed pretty fast and loose with adjusting so I'm feeling pretty good I'm in the ballpark... would be nice up at bat knocking one out obviously...
 

Schurkey

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Looking up the specs, the SBC rocker arm studs are 3/8" fine thread. Or 3/8" x 24 threads/inch.
Mr. Calculator tells me that 1" divided by 24 = .041" per thread. In order to make the rest
of this conversation easier (and easier to implement in the engine bay) let's just call it .040"
("Forty Thousanths") per full turn, and .010" per quarter turn.
^^^ The only thing you missed was rocker ratio vs. thread pitch.

Then NUT drops .041 per turn. The pushrod end of the rocker arm (and therefore the lifter plunger) drops more than that due to the lever action of the rocker. Given the nominal 1.5:1 rocker ratio of the SBC, the pushrod socket of the rocker arm drops closer to .062.
 

Road Trip

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^^^ The only thing you missed was rocker ratio vs. thread pitch.

Then NUT drops .041 per turn. The pushrod end of the rocker arm (and therefore the lifter plunger) drops more than that due to the lever action of the rocker. Given the nominal 1.5:1 rocker ratio of the SBC, the pushrod socket of the rocker arm drops closer to .062.

Schurkey, we're in total agreement at the valve tip regarding the 1.5:1
ratio. In my mind's eye my focus was the adjustment window inside the lifter
itself, and was assuming that from the fulcrum up to the pushrod tip was essentially
a 1:1 ratio, and the the 1.5 multiplication was between the fulcrum and the valve tip?

This could be wrong, but I'd have to stop, make both measurements,
and possibly amend the above?

At any rate, just wanted to introduce the correlation between wrench swinging
in degrees translated to up/down vertical adjustment inside the hydraulic lifter.

Never tried to describe this before via the written word, so I would categorize
reply #42 as version 0.1. No doubt there's room for improvement. :0)

Good input. More food for thought. Thanks for reading + thoughtful response. (!)

Cheers --

EDIT: Based on your explanation in reply #46, I went back to my reply #42 and
corrected the numbers. (For the benefit of future hydraulic lifter preload researchers.)
 
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Schurkey

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Rocker arm is essentially stationary on valve end. Nut drops .041. Pushrod end has to drop more than that.

Valve tip is the fulcrum. Cranking the nut down is the load. This results in force on the pushrod trying to shove it into the pushrod socket of the rocker arm at the top of the pushrod (arrow up) and a corresponding force shoving the bottom of the pushrod into the lifter plunger (not shown.)

If the load (rocker nut) moves the middle of the lever down by .041, the far end of the rocker (pushrod end) has to move farther than .041.
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But you're absolutely correct that the rotation of the nut in degrees has a corresponding depression of the lifter plunger in thousandths of an inch, once free-play is taken up, and with a nod of acceptance to some minimal amount of deflection in the valvetrain since nothing is absolutely rigid.
 

scott2093

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Jeez...Put it back together and it's idling like poo..
And I'm getting some kind of diesel knock sound for a couple of seconds at startup... sounds like it's coming from #1 but haven't looked further...

IAC counts are at 47 which seems off...O2 is lazy at 30-40mv..even with some throttle.....new Delco that's been fine....no cross counts at idle....see up to 4 cross counts if I give it some throttle...Everything else looks good...It's almost running like when I had too much preload the first time I adjusted preload cold but not as bad....

I did hit the alternator stud with the socket one time but alternator is outputting correct voltage... Wonder if I could have goofed something...? socket wasn't grounded except to me...
Not sure what that knock is at startup...It's not done that before...

Guess I'll do it again tomorrow and take some notes... I was alternating from closed to open loop so maybe I caught the o2 in closed....but iac doesn't seem right....If I give it some throttle it goes up to 60s in counts ... 47 seems high at idle?
Ugh...lol
timing at 0....

What's weird is the second time I did the adjustments and drove it when I had the residual smoke out of the exhaust, when I started this thread, , it ran better than ever... Then I adjusted everything again the next morning because I knew I rushed before because oil was going everywhere and I wanted to give it another shot. It ran great after that but not like the night before....



And here I am today going backwards....
 

scott2093

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The solution? Loosen until just clacking Wait a few seconds? Went quiet again? Loosen
a bit more. Wait. Repeat until you loosen the lifter, and it stays clacking steadily. NOW when
you tighten this valve until it is just quiet, you will reach the 'zero lash/zero preload' point.

You have no regained control over the adjustment of this valve.

Helpful hints while doing this:

* Have pen & paper. Write down exactly what it took to adjust each valve to the zero position.

* Work 1/4 turn (90° swing) at a time. This allows you to quantify all this in .010" increments if you wish,
or want to talk to a machinist, camshaft support hotline, etc.

Example:

#1 exhaust: 3 1/4 turns (~.030") ; no change in engine
#1 intake: 2 1/4 turns (~.020") ; no change in engine
#3 intake: 6 1/4 turns (~.060") ; engine smoothed out after adj.
#3 exhaust: 2 turns (~.020") ; no change in engine
(etc)
I'm trying to follow the part where there would be a change in engine. Are you saying that after I get to my zero lash/zero preload, I should then tighten 1/4 turns at a time and take notes for future reference but go back to zero lash and do my preferred preload? Just confused because it's mentioned in the context of finding the zero lash/zero preload by loosening . Sorry if it's obvious what you are saying.

I wish I lived out in the country. I'd be out there now stinging my eyes and aggravating my once broken rib but it'll have to wait 4 more hours..lol

yes 3/8" x 24 is what i was able to thread with the several threads above the rocker nut...just to confirm thread...

I did notice that there were a couple or few valves where the nuts just seemed tighter than the rest. I need to look at where they sit in relation to the others. But loosening and tightening was very smooth on most, these others not so much...
 

scott2093

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hmmm.
Decided to start prepping for the morning..
Couldn't tell you if I did this removing the cai just now or if it was bumped installing it earlier....Hoping the latter obviously...

I thought it was strange that the engine would run good after doing the adjustments but fall apart after I put everything back in it's place. Was suspecting a coincidence sensor going bad or something goofed from hitting the alternator stud with socket.
I notice that injector's push clip half on the firewall side is snapped so it probably makes for easier movement. Not sure if some loctite 498 I have here will repair that well enough... Will try..

Jeez... paranoid now the injector was hanging when I did my adjustments??that doesn't make sense...now I'm second guessing..as if forgetting if I set the preload on a valve and going through again wasn't enough before...
 

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scott2093

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Of course that was the issue... still very interested in my questions about taking notes on adjustments as it relates to loosening or tightening
Will see how a test drive goes....
 
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