Rocker adjustment

[needlenose]

There are a million examples of this, but I still have a question about it.

My lifters are already pressurized; there is no spring to them. I adjusted to zero-lash, + 1/2 turn. But I measured the valve height with a caliper before/after and the valve drops right at .025". This means I have a .025 gap in the valve seat. Seems like a terrific way to get a burnt valve to me.

It seems some of the examples show that the lifter can be pressed down a little after tight. Mine don't move at all. This is on cyl 1 at TDC and no lift on the lifters when looking down the drain hole.

Does the lifter soften a little when there is oil flow? All my hydro experience is working on 5.0 roller Fords; you just run them down tight. And that was a looong time ago.

Thanks!

 

[Supercharged111]

Is that on all valves? Are the lifters new? I had a couple on my 1500 that did that so I took them apart and cleaned them out when I did my cam. They were just gummed up inside and wouldn't travel properly. The valve spring should eventually overcome the lifter.

 

[Hipster]

There are a million examples of this, but I still have a question about it.

My lifters are already pressurized; there is no spring to them. I adjusted to zero-lash, + 1/2 turn. But I measured the valve height with a caliper before/after and the valve drops right at .025". This means I have a .025 gap in the valve seat. Seems like a terrific way to get a burnt valve to me. I have had stock hydraulic flat tappets hold the valve open at a half turn.

It seems some of the examples show that the lifter can be pressed down a little after tight. Mine don't move at all. This is on cyl 1 at TDC and no lift on the lifters when looking down the drain hole.

Does the lifter soften a little when there is oil flow? All my hydro experience is working on 5.0 roller Fords; you just run them down tight. And that was a looong time ago. I'll just toss this out, you want to make sure your on TDC compression stroke and not TDC exhaust stroke.

Thanks!

It can take quite a few minutes for the lifter to bleed off and the valve to settle down right after you adjust it if they were fully pumped when adjusting them that way. Typical standard type lifter plunger ends up about .030 down from the circlip that retains it on stock stuff. On a fresh build new cam etc. I usually dial indicate 1 to .030 to figure out whether it takes 1/4.2/3. or 1/2 to get there then run the rest.

Fast bleed type lifters don't hold oil pressure so you can push them and feel the spring and usually call for .030-.060 preload. Hy-rev type usually call for .001-003 preload. If using something other then stock type lifters look at the paperwork for the preload number.

.025 sound right about on the money. Set the adjustment at 1/2, wait 10 minutes, and come back and see it you can spin the pushrod, if so, then spin the engine to the next valve. If not back it off up to a 1/4. I'll just toss this out, you want to make sure your on TDC compression stroke and not TDC exhaust stroke.

 

[needlenose]

Thanks guys! I just replaced a single head with a bent ex valve, so everything else is stock and still installed.

I adjusted cyl 1 and left it untill I figured out what to do. So I will measure it again now that it has sat overnight.

 

[Schurkey]

The USUAL problem here is not getting "true" zero-lash. Plenty of folks go WAY PAST "zero lash" until the lifter plunger is totally collapsed, then they add their preload--which pushes the valve open.

The nearly-universal cause of this is the guy doing the work has been told to "spin" the pushrod as if that was a good way to determine zero lash. It's not. Both ends of the pushrod are polished and oiled, and they turn inside similarly polished sockets at the lifter plunger and rocker arm. Depending on the strength of your fingers, you can spin that ol' pushrod right to the point where the lifter plunger won't drop any farther.

One of the wonderful things about "Poly-lock" rocker arm adjusters is that they're low-friction. You can turn 'em with your fingers, no wrench needed. It's startlingly simple to find zero-lash when adjusting "Poly-locks".

Given a choice, I like to have the intake manifold OFF so I can see the lifter plunger. Since that's not always practical, wiggling the pushrod UP AND DOWN in-line with it's normal motion, or rocking the rocker arm, instead of "spinning" the pushrod keeps me out of trouble. As I turn the nut, I can feel the clearance decrease.

Or just adjust the rockers with the engine running. Messy, but really hard to screw up unless you're deaf.

 

[snipersm7]

I have a question in regards to valve adjustment. I have a new 5.7L vortec, have adjusted the valves acccording to Chilton's manuel. It indicates 3/4. What concerns me, is some intake valves are set on #1 top dead center, but when I rotate the crank 360 degrees and have #6 on top dead center and there is alot of slop or play in some rocker arms that I adjusted when #1 cyl was on top dead center? The cam is a factory roller.

 

[Schurkey]

some intake valves are set on #1 top dead center,

TDC INTAKE, or TDC EXHAUST. H-U-G-E difference.

when I rotate the crank 360 degrees and have #6 on top dead center and there is alot of slop or play in some rocker arms that I adjusted when #1 cyl was on top dead center? The cam is a factory roller.

You're doing it wrong.

Probably by not getting TDC Intake vs. TDC Exhaust correct.

Try this instead.

Mark the damper and timing pointer so you have a reference mark. Or, use the existing timing mark on the damper, and "0" on the timing pointer. Doesn't matter--either way will work. It DOES NOT MATTER where the crank is positioned, if you make your own mark.

Loosen ALL rocker arms so there's play in the pushrods.

Tighten ALL rocker arms to just eliminate the free play, but no tighter. This is called the zero-lash point. See my post above. Zero lash is critical, and easily screwed-up if you're spinning the pushrods instead of moving them up and down along their axis.

Turn the crank EXACTLY one revolution, so that whatever mark you're using lines up again.

Some rockers/pushrods will be loose again. Tighten ONLY the loose ones to just eliminate the free play in the pushrods, but no farther.

Tighten ALL rocker arms 3/4 turn.

Put the valve covers back on.

Have a beer. You're done.

(I got this method from Motordaddy. Thanks!)

 

[evilunclegrimace]

The factory manuals indicate ONE full turn from zero lash

 

[Schurkey]

The factory manuals indicate ONE full turn from zero lash

It's sort of like ride-height. The only ride height that folks hate is the one that the factory specifies. Lifted is good; slammed is good, stock is hateful.

Some guys want the lifter plunger towards the top of it's travel, so that it can't "pump up".
Some guys want the lifter plunger towards the bottom of it's travel, so that it can't collapse.

I said 3/4 because that's what Chilton told him.

One full turn as the factory specifies, works just fine on most applications.

 

[Jesse_Wenting]

So a few weeks ago I replaced my head gaskets and I at the time I ended up over tightening the rockers, so I went back in and reset zero lash from scratch plus a a half turn. After that there was a slight rattling so I went back in, gave them all an additional quarter turn and now the engine feels a bit rough through the entire rpm range.

Could a quarter turn really take me from a pinch loose to past acceptable preload?