The Stovebolt Site Forums The Shop Area Engine Shop valve lash terminology question

235 with hydraulics. Based on PO's other mistakes I want to check the valve lash cold at this time.I have read and read the threads on this (and the manuals)but the one question remains. At firing position each set of pushrods spin but some can be pushed down away from the rocker. (some can't)Actually pushing against the springs. Is this the "lash" that should be adjusted out or is this normal? I don't know what to do and would really appreciate some help.
Thanks

You should be able to push down on the pushrod side and create clearance. If not the lifter is siezed. When running they are filled with oil.

I also need to understand this. The hydraulic lifters pump up with oil as oil pressure is applied. This is a 'lagging' thing. It doesn't happen right away. During short starts and stops, I am also wondering how much it is happening and how you really know when they are pumped up properly.

So you have a cold engine, and you want to adjust the valve lash. From what I saw on Horsepower TV, you turn the engine until the intake (or exhaust) on a single cylinder is at the very top of its cycle. Once there, you set the valve to completely tight PLUS 1/4 turn. You then turn the engine until the next valve is at the top of its cycle and do the same... until you are done.

RIGHT?????? Please if you have no hydraulics, don't reply to this because they are totally different from solids. I may not have any idea what I am talking about, but its real important for you engine gurus to put this to rest once and for all.

If you do the valve adjustment procedure on my website, you can get it running okay, but that's a solid lifter procedure. I want to fine tune it for hydraulics. ??

Cassie and Deve, I'd be inclined to follow the factory manual procedure, adjusting both valves on each cylinder at top of compression stroke [valves closed], and ultimately when the engine is "normalized", which means at operating temperature ... the TV procedure should get them close enough to start and warm the engine, but there's also a procedure in the manual for assembling from scratch

Bill

I just found it interesting that if you follow the solid lifter procedure, it means you are using a gapping gauge to be precise when if using hydraulic lifters, you crank it down ALL the way plus 1/4. It does get you much closer to do the latter on hydraulics. I will look over the factory manual and I am sure I will learn something! Thanks!

you use a feeler guage for solids because there's supposed to be a gap, with hydraulics the "gap" is in the hydraulic pistons movement, they're adjusted to be partly compressed, which is why you need to do them hot [and oil filled]

Bill

If I'm reading this correctly you have your piston at TDC on compression stroke and your push rods for that piston are loose?

At each TDC each pushrod spins but sometimes one can be pushed down and the other is tight and can't be pushed down. What should I do? I think I have 3 or 4 that can't be moved other than spinning. The others will move down a little against spring pressure and then come back up. Which is correct?

Both are correct. Some lifters just bleed down quicker then others.

Run your engine till its up to operating temperature. Forget the cold setting as the books say.

Once warm, pull the rocker cover,

Rotate engine till both rocker arms on one cylinder are closed, you should be able to tell pretty easy. Watch the intake valve, when it shuts, go a little farther and stop.

Loosen the adjusting nut and back it off till the push rod rotates and has some slack

Going real easy and with a light touch, tighten the adjusting nut till the push rod just makes contact, rotating the pushrod as you tighten. Stop!

Now you have zero lash when they just make contact.
The correct setting is, 1/2 turn more after the contact point.

Don't worry about weather or not you can push down the lifter or spring, they will pump up when running.

Do both valves on one cylinder then rotate the engine to the next one. Watch each intake valve. Pulling the spark plugs will make turning it over much easier.

Valves are in this order,
Exh, int, int, exh, exh, int, int, exh, exh, int, int, exh

1/2 to 3/4 turn after zero lash is right in the center of the lifters travel.

DO NOT tighten the adjuster tight plus a 1/2 turn, this will only hold the valve open. You must find zero lash, and it takes a very light hand on the wrench. If you are off a slightly, thats OK, hydraulic lifters make up for that.


When you have them all set, the adjusting nuts should have approximately the same hight and threads showing. If one is way off from the others, recheck it,
Joe

Thanks Joe and others. This makes sense. However I don't see why bleed down is a factor since the engine has not run for months. Is it possible to test the lifters when the rocker arm nuts are loose and backed off by just pushing the pushrods to see if they go down and then return to the upper position themselves?

Howard

Here are the instructions for the 1955 car engine in the manual, stating the correct adjustment to be 1 1/2 turns. GM Manual Valve Adjustment The previous pages give a good explanation of the mechanism.

I have read this several times but I could never understand the "side play". There is no side play unless you push the pushrod down and then there is. That is what I don't totally understand. And then like I said some pushrods will not push down at all.

why are you 'pushing the rod down'? does it tell you to do that in the manual? the reason some will not push down may be because the last time the engine ran [years ago], that cylinder stopped with enough pressure on the lifter that it emptied ... and as pointed out above, those lifters need oiling via warming up the engine properly as called for in the manual ... what the manual is telling you is to tighten the adjuster just until there is no side play, ie: when the rocker is putting just enough pressure on the stem to stop that side play, there is no reason to manually push the rod down away from the rocker to obtain side play

Bill

OK. Thanks to you guys almost done. (back needed a rest!) The key was not to push the rods down. I had to do it cold but using a combination of Joe's procedure and the manual I'm sure it's in the ballpark. I got it to 0 lash and then tightened another 1/2 turn. It turned out to be 1/4-1/3 turn tighter than the PO's setting from a few years ago on each valve. It ran ok at that setting but had a small tick. Hopefully that will be gone, but if not I now understand the procedure and can do it again hot when it is running again. I appreciate all your input.
Howard

Sounds good Howard, the slight tick should be gone now. You can always add a 1/4 to each one if the feel the need. I tend to stay on the less is better when preloading the lifter. At higher rpm's you are less likely to hold a valve open.

The terms are little confusing when reading old manuals, the ideas are the same though.. Once you adjust a few it starts making sense. Coming from a drag race family, adjusting lifters was every week event it seemed like!

Joe

I have a rebuilt 56 235 in my 54 3/4 ton. It has hydraulic lifters. My question is this. Do you need to warm the motor when you live in Az. with 85 degree mornings? The lifters will quiet down in 5 to 6 blocks. We have about 3,000 miles on the truck. It drove with no problems from Missouri to Arizona in Feb. The lifters have never changed their clicking duration in the 3,000 miles.
Thanks
Sharon

Is it necessary to warm a motor with hydr. lifters when you live in Az. with 85 degree mornings? It is rebuilt with about 3,000 miles and the lifter clicking will go away in 5 to 6 blocks. Am I doing any harm? My truck pulled two motorcycles from Mo to Az in Feb with no problems.

Thanks
Sharon

Not so much of warming the motor, just be sure the oil is warm and the lifters are full. In your area, a few minutes or once around the block should be enough.

Sounds like you could have some loose ones, if it was a used engine, I might be concerned about a few dirty lifters. With good oil pressure and clean internals, you should not hear any tick if the truck is run everyday. Setting a while gives the oil time to bleed out, then you would a slight tick till the oil pressure comes up.

Joe

I may need to add this to my Blog but oil never bleeds out of a lifter when the engine is off.
They do bleed down but the oil just goes back into the top reservoir area of the lifter.
The first time the valve closes for that lifter the spring in the bottom of that lifter pushes the plunger back up and oil is drawn through the check valve back into the working area and the lifter is ready to go.
If they click on startup it is because the plunger gets stuck in the bottom of the body after they bleed down while the engine is off and cools. As the lifter warms the body expands more than the plunger and releases the plunger and the lifter starts working correctly. This can happen with new lifters where the plunger is too tight in the body, and it can happen on old lifters that have gummed up internally.
If it is happening with new lifters they will wear in after some wear in time and work correctly.

Dave, The engine has about 3,000 miles on a rebuild with new cam and lifters. I am using 20 w 50 Castrol here in Az just because it gets so hot. Maybe that's the problem. Thanks, you all give such quick answers.
Its a daily driver too.
Thanks
Sharon

Sharon, your oil choice is probable the reason for the delay in oil build up to the lifters. 20-50 is pretty thick and takes a while to heat up. 15-40 maybe a better choice.

Joe

Thanks Joe its about time for another change, I guess I'll try that thinner oil and see what happens. I'll keep an eye on the oil pressure to see what happens there.

Sharon

Let us know how it comes out.

20-50 is a really good oil for a well worn engine, it takes up a lot of room in the bearings, down side to it is it thick and takes more horse power to spin the pumps plus a lot longer to warm up. I have seen distributor gears worn 2/3s of the way away from thick oil, it just puts to much of a load on the gears trying to spin the pumps. You are right to run thick oil in high heat like you have, but modern oils are so much better then they were years ago, I think you can get away with thinner oil and still have the proper protection.

Joe

Joe H Thanks for the great info. This web site has great contributors. Going to work on the carb leak wed nite so the truck can sit allday on thursday and let the sealer harden.