Problems setting hydraulic lifter preload
Thread Starter
Drifting
Joined: Aug 2005
Posts: 1,289
Likes: 3
From: East Waterboro Maine
Problems setting hydraulic lifter preload
I'm in the process of preloading the rockers on my BBC and am running into an issue. When I tighten the rocker until there is some resistance while spinning the pushrod, then go another 1/2 turn, some of the springs start to compress a little instead of the lifter. I previously set the lifter preload without any issues (quite a while ago) and the engine ran great.
The engine has been in storage for a while now (over a year) and before putting it in storage I loosened all of the rocker arms. Now that I'm getting ready to fire it back up I'm having an issue with the lash adjustment.
Any suggestions on how to deal with this?
The engine has been in storage for a while now (over a year) and before putting it in storage I loosened all of the rocker arms. Now that I'm getting ready to fire it back up I'm having an issue with the lash adjustment.
Any suggestions on how to deal with this?
Last edited by Maine Vette; Nov 12, 2012 at 04:46 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
There is no "preloading" involved. You are trying to set the pushrod to the center of travel of the lifter piston. If you actually feel resistance when you tighten the nut, you have adjusted completely through the piston travel.
Instead of 'spinning' the pushrods as you tighten the adjustment, shake the pushrods up & down. When you feel all slop go out of the adjustment, tighten the nut an additional 1/2 turn.
Instead of 'spinning' the pushrods as you tighten the adjustment, shake the pushrods up & down. When you feel all slop go out of the adjustment, tighten the nut an additional 1/2 turn.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
When you tighten a loose rocker arm until all the lash is gone (hydraulic lifter), the plunger internal to the lifter is at the top of its travel. When you turn the rocker nut another 1/2 or 3/4 turn, this will eventually force the plunger down about .050 into the lifter, BUT if the lifter is already filled with oil, it will take several minutes before the oil can escape enough to let the plunger go down; in this case, the valve spring will depress a bit first until the oil can bleed out from below the plunger. Bottom line: Don't worry about it - by the time you're finished installing the valve covers, all will be ok, especially after the engine warms up.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
There is no "preloading" involved. You are trying to set the pushrod to the center of travel of the lifter piston. If you actually feel resistance when you tighten the nut, you have adjusted completely through the piston travel.
Instead of 'spinning' the pushrods as you tighten the adjustment, shake the pushrods up & down. When you feel all slop go out of the adjustment, tighten the nut an additional 1/2 turn.
Instead of 'spinning' the pushrods as you tighten the adjustment, shake the pushrods up & down. When you feel all slop go out of the adjustment, tighten the nut an additional 1/2 turn.
Otherwise you take the chance of valves hitting the pistons.
Thread Starter
Drifting
Joined: Aug 2005
Posts: 1,289
Likes: 3
From: East Waterboro Maine
I was installing the rocker arm nuts by tightening the nuts by hand and, at the moment they made contact with the rocker arm, I then turned the nut another half turn. Using this method some of the plungers were getting depressed, while others seemed totally bottomed out and the valve would start to open. I'm confident that I wasn't compressing the plunger when I was spinning on the nuts on by hand because I was watching the push rod and didn't see any movement.
The whole idea of there being oil in the lifter may have some merit. I did prime the engine last week and it has been pretty cold. Maybe the oil just can't get out of the lifter.
The whole idea of there being oil in the lifter may have some merit. I did prime the engine last week and it has been pretty cold. Maybe the oil just can't get out of the lifter.
Melting Slicks
Joined: Dec 2009
Posts: 3,222
Likes: 651
From: Thunder Bay
When you tighten a loose rocker arm until all the lash is gone (hydraulic lifter), the plunger internal to the lifter is at the top of its travel. When you turn the rocker nut another 1/2 or 3/4 turn, this will eventually force the plunger down about .050 into the lifter, BUT if the lifter is already filled with oil, it will take several minutes before the oil can escape enough to let the plunger go down; in this case, the valve spring will depress a bit first until the oil can bleed out from below the plunger. Bottom line: Don't worry about it - by the time you're finished installing the valve covers, all will be ok, especially after the engine warms up.
I've noticed the same thing when adjusting lifters. It just takes a little time for the oil to bleed out of the lifter.
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Drifting
Joined: Mar 2009
Posts: 1,253
Likes: 4
From: East Wenatchee (2hours from n e where) WA
When you tighten a loose rocker arm until all the lash is gone (hydraulic lifter), the plunger internal to the lifter is at the top of its travel. When you turn the rocker nut another 1/2 or 3/4 turn, this will eventually force the plunger down about .050 into the lifter, BUT if the lifter is already filled with oil, it will take several minutes before the oil can escape enough to let the plunger go down; in this case, the valve spring will depress a bit first until the oil can bleed out from below the plunger. Bottom line: Don't worry about it - by the time you're finished installing the valve covers, all will be ok, especially after the engine warms up.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
I'm in the process of preloading the rockers on my BBC and am running into an issue. When I tighten the rocker until there is some resistance while spinning the pushrod, then go another 1/2 turn, some of the springs start to compress a little instead of the lifter. I previously set the lifter preload without any issues (quite a while ago) and the engine ran great.
The engine has been in storage for a while now (over a year) and before putting it in storage I loosened all of the rocker arms. Now that I'm getting ready to fire it back up I'm having an issue with the lash adjustment.
Any suggestions on how to deal with this?
The engine has been in storage for a while now (over a year) and before putting it in storage I loosened all of the rocker arms. Now that I'm getting ready to fire it back up I'm having an issue with the lash adjustment.
Any suggestions on how to deal with this?
Bill "
I'm assuming you are following the correct procedure... adjusting each lifter when it is on the base circle of the cam ? Had to ask JIC.
Thread Starter
Drifting
Joined: Aug 2005
Posts: 1,289
Likes: 3
From: East Waterboro Maine
Yes, I'm adjusting with the lifter on the base circle of each lobe. I turned the crank to TDC and made sure the push rods for cylinder 1 were not moving as I approached the "TDC" mark on the balancer. I then adjusted the two rockers for cylinder 1. Then I turned the crank 90 degrees and adjusted the two rockers for cylinder 8. I continued this procedure, following the firing order of the engine, until all rockers were adjusted.
I'm following the procedure developed by Lars - http://www.corvette-restoration.com/...Valve_Lash.pdf
Thanks for the input guys. I did notice that after about 10 minutes or so the push rods that were previously compressing the valve spring loosened up and could be spun by hand (they couldn't be budged after they were originally adjusted). I think this probably confirms it was oil within the lifter that was causing the issue.
I'm following the procedure developed by Lars - http://www.corvette-restoration.com/...Valve_Lash.pdf
Thanks for the input guys. I did notice that after about 10 minutes or so the push rods that were previously compressing the valve spring loosened up and could be spun by hand (they couldn't be budged after they were originally adjusted). I think this probably confirms it was oil within the lifter that was causing the issue.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,361
From: At my Bar drinking and wrenching in Lafayette Colorado
Sounds normal and correct to me. If there is oil in the lifter when you set the lash, the 1/2 turn pre-load will, in fact, open the valve slightly. This will bleed off once you have rotated the engine 2 turns. Sounds like you're doing all the work accurately and correctly - good job.
Lars
Lars
Le Mans Master
Joined: Oct 2002
Posts: 7,098
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From: Las Vegas - Just stop perpetuating myths please.
Man,every-time i read a post on adjusting the lifters i read like a new science has been discovered with how the pushrods should feel. I think we need a list of possible correct feels and a list of incorrect feels to adjust the pushrods and post it as a sticky.
It would be funny except there must be a new motor here every week that eats itself on startup. Some of the results are hard not to laugh at though. I like the posts with some bent push rods and blame it on weak valve springs - think again bubba.
cardo0
It would be funny except there must be a new motor here every week that eats itself on startup. Some of the results are hard not to laugh at though. I like the posts with some bent push rods and blame it on weak valve springs - think again bubba.cardo0
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
Folks who have set lots of hydraulic lifters 'cold' have no trouble with the 'spin' method. But, first-timers have difficulty with it, if someone who is experienced didn't show them how to do it 'in person'.
You can describe the 'shake' method over the computer and a newbie doesn't seem to have problems with doing it right. The folks who ask about how to do it are, in fact, newbies. That's the part that is often overlooked by folks who respond to them.
You can describe the 'shake' method over the computer and a newbie doesn't seem to have problems with doing it right. The folks who ask about how to do it are, in fact, newbies. That's the part that is often overlooked by folks who respond to them.
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
I used try explain how to adj vlvs by the spin method but ya know there are plenty here that still argue against it and the owners seem to ignore what i said regardless. My feeling is many new enthusiasts have a dangerous amount of overconfidence and may only learn the hard way by themselves.
I think u have an exceptional understanding of vlv adjustment 71. And i nominate you to provide assistance to all requests or even perceived weaknesses in skill.
Yes, for any new enthusiast (newbie) cam swapping or rebuilding his/her engine we will call on u to provided coaching/consulting.
I will support your posts at every chance in an effort to rid the forum of wiped cams and start up engine self-destruction.
U are the one to carry the torch 71, for the betterment of this forum,
cardo0
I think u have an exceptional understanding of vlv adjustment 71.
And i nominate you to provide assistance to all requests or even perceived weaknesses in skill. Yes, for any new enthusiast (newbie) cam swapping or rebuilding his/her engine we will call on u to provided coaching/consulting. I will support your posts at every chance in an effort to rid the forum of wiped cams and start up engine self-destruction.U are the one to carry the torch 71, for the betterment of this forum,
cardo0
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
I have no problem with the 'spin' method. I also have no problem with the 'shake' method. Either will work as well as the other, IF the person applying said method understands it [correctly] and can tell when "zero lash" is actually attained.
My only interest is to help folks who ask for it, and that what I describe in "words" can have a good likelihood of being executed by folks with not a lot of actual experience. This stuff isn't "rocket science"; but if you have no prior knowledge or experience, simple engine work can seem like rocket science to them. Our task (all of us trying to share knowledge/experience on this Forum) is to pass on usable info to those in need. I think we all need to 'share' "waving the flag" on this one. It's not something just one person can do.
My only interest is to help folks who ask for it, and that what I describe in "words" can have a good likelihood of being executed by folks with not a lot of actual experience. This stuff isn't "rocket science"; but if you have no prior knowledge or experience, simple engine work can seem like rocket science to them. Our task (all of us trying to share knowledge/experience on this Forum) is to pass on usable info to those in need. I think we all need to 'share' "waving the flag" on this one. It's not something just one person can do.