jshepard77

I hope this isn't too long for a simple issue...

I replaced my old valve seals this week, which I had never done before (took me all week). All went well and after all the seals were replaced and the rockers were back on, I went through the process of adjusting the valve lash. As far as I know (and it's a pretty good assumption), the engine is pretty stock and is a 350 small block. So I believe the lifters are hydraulic.

I went through the shop manual process for adjusting lash. I set the #1 piston to TDC, then adjusted a bunch of rockers (it lists which ones in the book). Then I rotated once to #6 TDC and adjusted the other rockers. The book says to adjust to zero lash, then one turn further. I had read up in the forum here about beginners having a hard time finding that zero lash point, as it takes a bit of an experienced feel. So I turned until I felt a slight change/drag on the pushrod, and then turned 1/4 turn. My thinking is that perhaps I would be a little late in feeling the zero lash point... and one turn past zero seemed to be a bit much from what I read. Also I thought that it's better to be loose than tight, from a potential damage standpoint.

After I had adjusted all the rockers, I turned the engine over a bunch of times. I checked the compression on all cylinders and it was pretty much 170 on all. Then I went over each rocker and wiggled it to be sure that it was tight. One was loose (#2 exhaust I think). I re-adjusted that rocker and got no compression on that cylinder. I then rotated the engine to the correct TDC point for that valve and re-adjusted again. I was back to 170, but the rocker was loose at different points in the engine cycle. I figured "oh well, follow the book and see what happens" I started the engine. I get a definite tapping sound from the engine. Seems obvious to me that I didn't adjust the lash quite right and I'm a little loose. I can't quite tell if the tapping is coming from all over, or just that #2 valve.

I have a few questions:

1) It's a pain in the but to get the valve covers off to make these adjustments. I clearly have to take them off again to make an adjustment. Should I abandon the #1 and #6 TDC procedure? I've seen people adjusting without regard for the timing mark, by adjusting the exhaust rocker when the intake valve is open and vice versa...or something like that. I don't have old valve covers to cut a window in to adjust them while running.

2) I tested my compression a couple weeks ago before all this. It was 145-150 across the board. Now they are reading at 170 on all. Is that a concern? I guess that's partly an effect of my valves closing tighter now? Maybe an effect of the new seals I put in? I just want to be sure that it's not too concerning. I kind of thought that more is better with compression.

3) I have a mechanic that I can take this to if I need to. Is it bad to run this engine with a tapping for a bit (across town). Or, should I not let it run at all until I re-adjust. I just don't know how quickly the loose rockers will cause damage to things.

Sorry for the long post. Half these details may be irrelevant.

TimAT

I use the book method for initial setting, then start the engine with the 1 cover off and re-adjust, then do the other side. It's messy for sure. Back off until it rattles, tighten it until it just quits, then another 1/4 turn. Hasn't missed since 1971.

wombvette

You dont understand that the valves on a hydraulic cam, get loose when the oil is not circulating, so when you readjusted that valve you tightened it too much.

Use Tim`s method and tighten them just enough to stop the tick. But for a stock engine, one more turn is correct to center the plunger.

1971corvette

Since you have it close and it runs,do as stated above,one side at a time,back off one at a time ,tighten until the noise on that one stops and I tighten another 1/2 turn.
There are some clips availabe to cover the holes in the tips of the rocker arms,they help control the oil mess as you adjust.
These serve the same as what you mentioned with a valve cover with a window cut in it.

Sounds like you are on the right track,give us an update when you finish your chore.

jshepard77

I just wanted to update this thread...it's nice to see how the issues resolve sometimes.

I didn't adjust the lash with the engine running...i just didn't want to make the mess. I'm going to keep an eye out on ebay or craigslist for some old cheap rocker covers and cut some windows in them. I cleaned and re-painted mine during this process and can't bring myself to cut them. But I plan on revisiting that process later.

Instead, I used the process of adjusting the intake when the exhaust just opens and the exhaust when the intake is just closing (or something to that effect...I had a cheat sheet in front of me because I was forgetting when to adjust each one). What I found was that the #2 exhaust and the #3 intake were both pretty loose. Just must have done them wrong before.

In each case what I noticed was that when I adjusted to 1/4 past zero lash, I lost compression in the cylinder. Part of this could be attributed to me establishing the zero lash point incorrectly...but I would turn the nut back and forth a few times to hone in on that zero lash point...so if I was off, I don't think it was my much more than 1/8 turn or so. What I eventually had to do was turn to the point I lost compression, then while turning the engine over, I would back the nut off until the compression returned to the cylinder.

Now I'm running very well with no tapping. I don't think I'm adjusted perfectly, and I think that I'll revisit it later with the cut valve cover method. But for now I think it's pretty good.

Thanks for the suggestions and comments!

7T1vette

The hydraulic lifters need to be submerged in oil and then "pumped up" using a pushrod. Chances are, a couple of your lifters were 'dry' and just felt loose because they were 'empty'.

71406

Just curious, why the difference in lash between a stock and non-stock motor? I always thought you centered the plunger but many people on this forum state 1/4 turn past zero lash. Again, just curious, not arguing the point.

wombvette

It is said for HP applications the lifters don't have as much tendency to pump up if adjusted loose. That's why people will adjust 1/4 turn instead of 1 full turn. Original specs call for one turn.

MotorHead

When you adjust a hydraulic lifter it doesn't matter if there is any oil in it or not, soaking then just gets some oil into the new lifter so when you start it the lifter isn't dry inside and and pumps a few cycles dry depending on how far forward the lifter is before oil gets to it.

When you are getting zero lash you can turn the pushrod or move it up and down. I find it difficult with guide plates to move it up and down unless the intake is off.

The extra 1/4, 1/2, full turn whatever in merely pressing down on the spring inside the lifter, no oil necessary

I also like to do it running, easy job once you get two old valve covers on with a slot in them to adjust the valves it takes 5 minutes

wiseman79

When I've got the top end apart for valve seals or whatever, and when everything is going back together with the same parts, I've always measured how much thread on the rocker stud is showing from the nut with a mic. I check them all but they are usually all almost identical measurements. Then when I reassemble I tighten down until again that much thread is showing. That's plenty accurate to get it started then just to make certain I'm there I do the above process of backing off till it ticks then going 1 turn past them getting quiet.

jshepard77

Before I took the rockers off the first time, I marked each nut at 12:00 as a reference for when I put everything back together. The thinking is that after adjusting the rockers again, the mark on the nut should be in about the same 12:00 location. Of course my marks were all over the place...anywhere but 12:00. I think that's a similar idea to measuring the exposed threads on the stud.

I have a lead on an old valve cover, so I should be able to adjust that way shortly.

c69vete

Here is my tip to keep down the oil mess when adjusting rockers. I use a strip of heavy duty aluminum foil to catch and return the oil to the head. The bottom edge tucked into the lip of the head and wrapped around the ends a bit. Make it as high as needed for the type of rockers you have. Works great, easy clean up, no cutting up good valve covers and CHEAP.

billla

Hydraulic lifters do not need to be "pumped up" to adjust - they have a spring that will hold the cup up very firmly. Take an old hydraulic lifter, put it on the bench and push down on the cup just to get a feel for this.

There's also no reason to set valve lash running, and doing so will almost always result in far too much preload. No engine builder or tuning shop does it this way, and with a little experience you can easily and consistently set this correctly. Too much preload means lost power and the possibility of premature cam wear.

If you were losing compression with that minimal amount of preload, most likely you weren't finding zero lash quite right - it does take a bit of "touch".

This is a repost of an article I wrote for another site...

There are two aspects to correct hydraulic lifter adjustment:

Making sure you have the engine in the right place to adjust. Many mechanisms for this and most are good...except for doing it running which does nothing but make a mess. The two methods that work the best are the exhaust opening/intake closing (EO/IC) method (always works) and the companion cylinder method (good for all but the most extreme cams).

Both of this require you to either manually position the engine using a tool that fits on the flywheel/flexplate (PITA), or more commonly to "bump" the engine with the starter. "Bumping" is a bunch easier with a remote starter switch.
Finding zero lash. Reliably finding zero lash is critical - and the most common area people make a mistake on - generally on the way-too-tight side. The process is very easy; with the engine in the right position as noted above, loosen the rocker to be adjusted until it's fully loose. Slowly roll the pushrod between your fingers while tightening the rocker...and the FIRST TIME you feel ANY DRAG AT ALL on rolling the pushrod is zero lash. Go back and forth a few times until you can comfortably, consistently find zero lash.

Once you've found zero lash set the appopriate preload - refer to your cam instructions or the service manual. Most but not all aftermarket cams want 1/2 turn, most but not all factory cams want 1 turn.

7T1vette

If you are familiar with adjusting hydraulic lifters, then there is no "need" for pumping them up. But, if you do this once every 10 years...or maybe just once, having oil in them makes it easier to 'find' the zero lash point [IMO]. I have never liked the 'spinning push rod' method; especially for novices trying to set them for the first time. I much prefer the 'shake the push rod' method for finding zero lash point.

MotorHead

My method is simple for a street or even semi-radical street cam. Both #1 cylinder and #6 cylinder fire at the O deg mark ( tuned and advanced this could be 15-20 deg doesn't matter )

When the #1 cylinder fires the #6 cylinder is going to be in overlap. There is going to be pressure on both rockers but what is happening is the exhaust valve is closing and the intake is opening.

I have a degreed balancer all the way around marking the entire 360deg now but this is the first one. Before that what I did and this is what my buddy does at his engine shop is:

When you are getting close to TDC on #1 there is very little movement of the rockers on that cylinder. You look at #6 and you will see movement on the exhaust valve closing. Now once the exhaust valve stops moving the intake will start to open. This is overlap on the #6 cylinder and once both rockers look equal you can be assured you are within 1 or 2 deg of TDC on #1 cylinder and you can look at the balancer and see you are right on the money. Now you can adjust both intake and exhaust on #1 cylinder.

Next you rotate the motor to 45 deg to adjust #8 rockers exactly the same only this time you are looking for the rockers to be equal on #5 and so on according to the firing order below. I have done this for many years and while it sounds complicated it is not

1843
6572

GM and other manufactures never adjust the valves with the motor running because it is a new engine and you have to set them with the motor off just to get the motor running in first place. And this is how they tell they tell their
technicians to do it from that point forward I assume.


I have had ticks after setting the valves with the motor not running after a year or two for whatever reason and there are many. The simple fix is to use the cutout valve covers and that method has never failed me. You back the rocker off until you hear it ticking then crank the nut down until the noise goes away and turn it down a little more 1/2 turn or whatever turns your crank

billla

I'm interested in how having oil in the lifters makes it easier to find zero lash. The cup is at exactly the same height either way...so how does this help? It's a sincere interest.



I understand there are different preferences for how to move the pushrod to find zero lash. Personally, I find it easier to do and teach the rolling pushrod method, but whatever is used it needs to be practiced until it can be done consistently.

I don't know of a single aftermarket engine builder that adjusts the valves with the engine running - even on the dyno. Does anyone?

For hydraulic cams, they usually are a one-and-done set. Most commonly if it's going out of adjustment on a regular basis it's probably a rocker nut that's loosening over time.

noonie

You have no choice the first time.

Just easier to do it running afterwards.

jshepard77

This sounds about like I expected...there are about as many "best way" methods to adjusting as there are people working on cars. I think everyone's way is correct, if it gets the job done for you.

At this point I've used the "companion cylinder" method to get started, resulting in a little ticking. I then used the "EO/IC" method to basically locate the loose rockers (there were 2) and re-adjust them. After that the engine sounds good, has good compression, accelerates and idles better than it ever has. My thinking was to re-visit this with the engine running, but now I'm thinking to leave well enough alone and call it good. I have plenty of other projects waiting for me on this car

7T1vette

Cold oil in the lifters provides a bit more resistance to the compression of the pushrods when searching for 'zero lash'. As I stated, an experienced person doesn't need to do that. A novice can use all the 'help' he/she can get.

tonak

I recently replaced all valve springs and went with the EO/IC and spinning of rods to get the engine started. I then went to the open valve cover to adjust it while running. As far as experience, it was the first and potentially the last time I will do this. My educated guess is that if lash is set without the engine running, one of the first things checked is whether or not there is lifter click upon running it. Setting lash on a car is more difficult than during the building phase, which partly explains why builders don't do it while the engine is running. Just my personal observations...