I did do a search about "valve adjustment".

The comments and experiences are very different about tighten the valve rocker arm nuts:

1.- ZERO lash + 0 turn .
2.- ZERO lash + 1/4 turn.
3.- ZERO lash + 1/2 turn.

How could run the engine with these alternatives?

Example:

Alternative 1: More rich, smooth, too many noise, etc.

Alternative 2: Lean mixture, fuel economy, etc., etc.

Alt. 3: Other possibilities, etc., etc.

Thanks for your opinnion.

 

The goal in adjusting the valves correctly is to have them seal completely when necessary and open as much as necessary. The point of adjusting the valves properly is to link each individual piece of the valvetrain together - camshaft to lifter to pushrod to rocker arm to valve - and in doing that create a smooth properly running engine and assure the lifetime of the parts. If you've got your lash set too loose for a while it's going to shorten the life of many little parts of your engine and make noise, and too tight could run badly or not at all. I always go half of a turn after zero lash.

I don't completely understand your second question. The valves sealing incorrectly will only cause the engine to run badly - which may include noise, roughness, and I guess valves that do not seal could cause the o2 sensor to sense a rich condition and adjust accordingly. Valve adjustment must be done within certain specs(let's say 1/4 to 1/2 turn after zero lash, just to give some numbers). If your engine is not there, it's not right and it won't run right.

 

O.K., Thanks,

The second question is if it's possible to move, control or "manage" some parameters like power, emissions, fuel consumption, etc. using different "valve adjustments turns" (0, 1/4, 1/2...).

Yesterday, I started with valve adj.. I used ZERO lash + 0 turns(only 1 socket + my hand pressure, turning the rocker arm nuts with hot engine). At the end, the idle at P/N was very good, but when I put "Drive" the power was very bad and some loud noises, like CLANK, CLANK, ..CLUNK, TUNG!, coming from valves, camshaft or so, were heard

 

The whole point to adding turns after you can't turn the pushrod anymore is to give the lifter some "preload" Since the lifters are hydraulic, they must have some oil in there to ensure complete transfer of the cam lobe lift pushing up on the rocker arm.
You spin the pushrod while tightening the rocker nut, and the very point that you can no longer turn it is 0 lash. You must put at least 1/4 to 1/2 additional turn of the adjustment nut in order to provide "pump up" clearance (internal to lifter) or else the lifter will accumulate air inside the passage, preventing the oil from going up into the pushrod and subsequently lubricating the rocker arm.

Loosen them all up, then follow the manual's directions for adjusting the rockers, with 1/2 turn after 0 lash. It will run smoothly and all the valves will operate correctly.

hth,

 

Umm, I thought Zero lash was spinning it till you feel slight resistance, that's the way I was told and the way I did it.

 

I agree with Mark.

Just remember not to over tighten the adjustment or you will have a good chance of burning a valve from the valve not staying on the seat long enough to transfer heat. I killed a set of heads playing around with this same topic.

From all the engine guys I have hung out with (TRACO, KB Engineering, Lingenfelter, Paul Pfapf, Dick Gazon, Vic Edelebrock and others) I will have to say this has been a great topic of discussion over the years.

The general consensus is: With engine running and warm, backoff the nut until it makes noise. Tighten until noise stops, add 1/4 turn. Move to next nut.....

 

You're both correct. Spinning an oiled pushrod in your hand is impossible with even a slight drag if you grip it lightly. When you're at zero lash if you continue to grip the pushrod lightly, you should not be able to spin it because of the oil. If the pushrod is dry enough you're going to encounter some drag before your ability to spin it ends.

 

Hydraulic lifters "self-adjust" to a zero-lash condition. If you adjust them while the engine is running, you'll notice that after the clacking stops (the "zero-turn" point), turning any further causes the engine to miss - for awhile, then it smooths out again as they adjust to zero lash. The factory used to adjust them to one turn down (not sure what they've been doing lately), which put the lifter plunger at about the mid-point of its total possible travel.

However, hot rodders who put more agressive cams in their engines noticed that the maximum RPMs they could reach was reduced if they went a full turn down, because at high RPMs, the lifters weren't able to "adjust" as well, causing a condition typically called "pump-up", which would leave the plunger higher up in the lifter bore, causing the valve to remain slightly open. The hot rodders went to 1/2 turn down to solve this "pump-up" problem.

Zero turns down will provide no benefit, and will likely clatter. Possibly also keep the valves from operating consitent relative to each other. 1/2 turn seems to work under most conditions, I've never tried 1/4 turn personally. But, there wouldn't be any emissions or economy differences between 1/4 and 1/2 turn down (assuming the lifters are in good condition).

Solid lifters - that's a whole 'nuther story...

 

The most accurate way is with a dial indicator. Adjust to zero lash. It takes very little effort to go beyond zero lash. You don't want the rocker to start pushing down on the pushrod. The most accurate way is to now have the rocker tighten down on the pushrod so that the pushrod moves down .030" into the lifter after finding zero lash. .030" isn't very much but is very close to 1/2 turn. One way of finding zero lash is with a feeler gauge. Use a .0015" feeler gauge on the valve. When you tighten the rocker, stop when there's drag felt on the feeler gauge. It will only be brief because the hydraulic lifter will release the pressure if tightened too much.

It all has to do with the way a hydraulic lifter works. The .030" preload sets the internal parts of the lifter to where they're supposed to be.

 

Thanks for the replies,
but the last problem to solve is:

Why ZERO lash position change from day to day?.

Yesterday, I put all the valves at ZERO lash tighting the nuts only with a long socket in my hands (engine running at normal temp.). No more tighten was possible.

Today, was possible tighten some nuts again. What happened in the night?

When I can arrive to final ZERO lash in order to add 1/4 or 1/2 turns?.

Regards,

Denis V.

 

When there's no oil pressure the lifters bleed down. The only way to readjust them is to back the rockers right off and allow the plunger inside the lifter to rise up. If you try to tighten the rocker down further after the lifter bleeds down, you're just preloading the lifter more and can cause damage if the pushrod is pushed down too far.

Once hydraulic lifters have been adjusted properly the first time they should never lose adjustment unless the rocker nut backs off. If a rocker starts to get noisy and the rocker nut hasn't backed off there's usually 2 things that can cause it. A lifter can be collapsed. It won't pump up with oil pressure. Or a cam lobe is wiped out. This can be seen by watching the rocker when the engine is running. If the rocker moves very little compared to the others then there's no cam lobe left.

 

When I used to beat on the car a bunch, I actually had to adjust more often.....So, I looked into why.

I found out that the nuts were a little used, from many years, and I went a bought a new set at GM.....problem went away.

Secondly, I found that the studs were slightly pulling out too. So, off with the heads and I ended up putting pins in the press-in studs. (it was a crate motor, so there were no screw-ins from factory).

Food for thought

 

Hmmm: Nuts used: good topic.

Thanks.

 

UUAAAAAAAAAHHH. Problem fixed!


TWO NUTS ARE BAD!


(then, ZERO lash is changing and 1/4 or 1/2 turn can be 0 or (-) 1/2 turn and idle is irregular).


I'll buy new rocker arm nuts.



Thanks for the help and replies.


Denis V.

 

I often just buy some regular nuts at the parts store to use as jam nuts...

 

I used diferent methods for comparison purposes.

Engine warm, engine hot, engine running, engine not running, turning engine with a socket + torque wrench, cold & warm, etc.

With all of them (using Zero + 1/2 turn) I arrived to similar rocker nut position: about 1 milimeter between the top of the nut and top of the stud = all the nuts at the "same level" (other valve adjustment system?).


Regards,

Denis V.

 

Good deal.......