Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

[Wayne M.]

Using method for cold engine; TDC mark on harmonic balancer opposite "0" degree mark on timing tab. Confirm piston #1 cyl at top [thru spark plug hole]; adjust following valves: Exhaust 1, 3, 4, 8; Intakes 1, 2, 5, 7.

Adjust valves by backing off rocker arm nut until play in valve push rod, then tighten nut to remove all clearance, check by rotating push rod between thumb and forefinger until resistance makes it difficult to rotate any further.

What do you guys do next ? tighten nut an additional full turn, or a fraction of a turn ? Chevy says full, but I've heard other preferences.

Finish the other half of the valves by rotating crank one full turn (again, balancer mark opposite "0" timing tab [ie. #6 cyl is at TDC]; adjust the following: Exhaust 2, 5, 6, 7; Intakes 3, 4, 6, 8.

[George T.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

I turn the nut 3/4 turn

[Duke W.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

You can't always tell by just turning the pushrod, but wiggling it up and down will definitely tell you when zero clearance is reached, so that's what I recommend.

The amount to turn beyond zero clearance has been debated about as much as engine oil.

The more you turn it down the more wear allowance in the adjustment, but the longer the engine will take to recover from pump up.

So anything between about 1/8 turn (if you expect to hit pump-up speed once in a while) to one full turn (if you never want to remove the valve cover for the rest of your life) is okay, and the best compromise is probably 1/2.

New valvetrain parts might see a little run-in wear, so maybe 3/4 turn. If you are just readjusting a well run-in engine in good operating condition that doesn't show any signs of excess wear in the valve train, I'd go 1/2 turn.

Duke

[Ronald L.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

Duke,

I have tick, isolated to mostly #2 and #3 valve train and that pair of rocker arms seemed looser that the others. 66-427, supposedly 50K miles on a relatively un touched engine.

I was thinking to take the rockers off, inspect for wear and re install.

What I am uncertain of is how to do this knowing that the lifters might not be "pumped up, or worse, if that one is partially plugged - collapsed.

What do you reccomend as a diagnosis process, re install and adjustment included?

[William P.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

Rather than putting the engine on Top Dead Center and setting half of the lifters and then rolling it 360 to do the other half I prefer to use a remote starter switch hooked to the solenoid.
I then do each cyl individually . Bump the engine untill the exhaust valve starts to open and set the intake valve, bump it again until the intake valve just closes and adjust the exhaust . Do each cyl 1 at a time .
Bill Purdy

[Ronald L.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

I have one of those and that makes a lot of sense.

What I am looking for is should I take them apart, pull lifters and can I see if one of them is - not pumping up by looking? I do not expect to see any varnish on moving part surfaces in that I have pull the covers before and looked to see if anything is abnormal.

And on re-install a clear torque down, with the hydraulics I've heard 1 1.5 1.25 turns past contact, etc Not sure what is best in this regard.

Thanks.

[Duke W.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

Duke,

I have tick, isolated to mostly #2 and #3 valve train and that pair of rocker arms seemed looser that the others. 66-427, supposedly 50K miles on a relatively un touched engine.

I was thinking to take the rockers off, inspect for wear and re install.

What I am uncertain of is how to do this knowing that the lifters might not be "pumped up, or worse, if that one is partially plugged - collapsed.

What do you reccomend as a diagnosis process, re install and adjustment included?

The rocker arms with a hydraulic lifter cam should never be "loose" like they are with a mechanical lifter cam and the lifter on the base circle. I assume you have the 390 HP engine with a hydraulic lifter camshaft.

Removing the rocker/ball and pushrod for a wear inspection makes sense and is not hard to do. Also, carefully inspect the valve springs. If all is okay reassemble with a half-turn preload and see what happens.

If it there is still ticking you either have to live with it or pull the manifold to inspect the lifters.

Duke

[Ronald L.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

Duke,
Yes 390 HP.

When you say loose, say I go out for a drive, come back, car is hot, immediately pull the covers, in any position there should be no looseness?

What I am thinking since we do not know what happened in 1975, was to loosen and re adjust so nothing is set too tight.

Recall from another thread I am close to re-installing the original intake so looking at the lifters - what to look for, or just change them is a piece of the guidance I'm looking for.

[Duke W.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

Either hot or cold they should not be loose in any position including when the lifter is on the base circle.

It would be a good idea to loosen all and readjust all to a half-turn preload.

Hydraulic lifters can be taken apart and cleaned, although most just change them if they are sticky.

Others with more hydraulic lifter experience may be able to offer advice. I've never owned a car with hydraulic lifters.

Make sure you are using C-category oil. Also, there are some commercially available supplements with a heavy dose of detergent that can unstick sticky lifters.

Duke

[Chuck S.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

My experience with Chevrolet hydraulic lifters is that improper adjustment does not cause a "tick", but more like a ominous hollow knock. It's louder than you would expect for a lifter. I thought something terrible was wrong with my new Chevy until I discovered one hydraulic lifter out of adjustment.

The CSM gives instructions on how to adjust hydraulic lifters cold and/or hot (running). Adjust them cold as directed. Then with the engine warm and running, you turn out the rocker adjustment until you just begin to get noise. Turn in the adjustment until the "knock" just disappears, then add in the amount of preload you desire.

[Timothy B.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

How much of a risk is there if new lifters are used with a good used camshaft. I have a 097 camshaft that looks to be in very nice condition but the lifters were tossed.

If the lifters are treated with 600 sandpaper will this be smooth enough to use on a used camshaft..

[Joe C.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

How much of a risk is there if new lifters are used with a good used camshaft. I have a 097 camshaft that looks to be in very nice condition but the lifters were tossed.

If the lifters are treated with 600 sandpaper will this be smooth enough to use on a used camshaft..

Post a few photos of your used cam lobes.

Lifter must have at least .001" (to .002") crown on its foot. In other words must be convex with .001" - .002" mound in center.
Use wet dry paper, 600-1000 grit with a surface plate. Keep the paper wet with WD40 or light machine oil. Use a figure-of-eight pattern while keeping the lifter square to the surface plate. Rotate the lifter 1/4 turn in your grip every 15 seconds or so.

A "quick" check is done by putting 2 finished lifters foot-to-foot. You should see light all around the outsides of both.

[Ronald L.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

FWIW - the 1966 CSM has zippo about adjusting hydraulics. One sentence on the solids.

I pulled the LH cover, all clean, rocker tips polished, no wear. Re set each to half turn as described above closed. #5 intake is still ticking, cold, when hot still and I put another half turn on that - when hot to a lesser degree #5 & 7 intakes ticked too with the hose test, but #5 I is the one making the noise. Heard worse in the car just off idle.

I noticed that rocker you could rock slightly to the side when cold.

[Chuck S.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

FWIW - the 1966 CSM has zippo about adjusting hydraulics. One sentence on the solids.

I pulled the LH cover, all clean, rocker tips polished, no wear. Re set each to half turn as described above closed. #5 intake is still ticking, cold, when hot still and I put another half turn on that - when hot to a lesser degree #5 & 7 intakes ticked too with the hose test, but #5 I is the one making the noise. Heard worse in the car just off idle.

I noticed that rocker you could rock slightly to the side when cold.

Just to be clear, CSM stands for "Chassis Service Manual", the original GM Chevrolet version, ST-72, published by Helms in 1966.

I can't attest to what other brand manuals or reproduction manuals include or don't include. I found the information I needed in my original Helms version ordered more than 44 years ago, and it's still there.

Cold adjustment of hydraulic lifters is covered in the Engine Mechanical section, page 6-29 (about six column inches). Hot adjustment of hydraulic lifters is covered in the Engine Tune-Up section, page 6-13, in six easy steps (about five column inches).

[John H.]

Re: Late '60s BB hydraulic valves adjust rocker nut down (full turn, 1/2 or 1/4 ?)

How much of a risk is there if new lifters are used with a good used camshaft. I have a 097 camshaft that looks to be in very nice condition but the lifters were tossed.

If the lifters are treated with 600 sandpaper will this be smooth enough to use on a used camshaft..

Tim -

There will be other opinions on this, but mine is that I wouldn't do it; that camshaft has worn-in to that set of lifters, and may not be happy with a set of new lifters. You might get lucky and not have a problem, but on the other hand, if not, you've got a mess on your hands that requires a full engine teardown to resolve when lobes start disappearing.