Valve Lash Adjustment

[jor]

87 Suburban, 5.7L TBI

I've been doing a lot of work on this Suburban (running gear) and decided to replace the valve stem seals while I was at it. All went well (I thought). Anyhow, I started it this morning and boy does it run rough. I checked the firing order and all is well with that. The only thing I can think of is I messed up on the valve lash. I'm following the shop manual instructions: putting it at TDC on #1 and adjusting the indicated I and E rockers, then moving to TDC on #6 and doing the same. I guess I could have messed up there. Anyhow, one question. The book says to take it to zero lash so I'm spinning the push rod and when it stops spinning I figure that's zero. Then the book indicates to tighten it "one full turn" so I am tightening each one 360 degrees or four 1/4 turns on a ratchet. I am making these babies too tight? Thanks.
jor

 

[ryoken]

yup... I go 3/4 turn on sb's... and I actually don't go till they wont spin.. just when they start to bind...

 

[trikstark5]

There is always the old fashion way. It is a little messy unless you purchase the clips for the rockers, but all you have to do is remove the valve, install the clips, and loosen one rocker at a time, with the engine running until you hear the valve start tapping, then tighten 3/4's of a turn and it is set. You can do all of them that way, but I wouldn't recommend it unless you have the clips so oil doesn't go everywhere.

 

[ryoken]

even with the clips, it'll dribble over the head lip sometimes... I have old sets of BB and SB vc's cut with windows for doing them with the clips... Been hanging around the garage forever.. habit from back in the days of building solid cam Mopars...

 

[dyeager535]

Way too tight. You tighten the rockers while spinning the pushrod, as soon as you feel DRAG on the pushrod, that is zero lash. You may need to loosen/tighten the rocker nut a couple of times to get the feel for it. Then whatever setting you believe from there. Typically in the area of 1/2 turn more.

You were doing it with each valve closed, correct?

Hope you didn't wipe the cam.

 

[jor]

Way too tight? OK. I was trying to follow the shop manual instructions exactly. It indicates on #1 TDC you adjust exhaust 1,3,4 & 8 and intake 1,2 5 & 7. Then the others on #6 TDC. Here's what the manual says:
"Back out the adj nut until lash is felt at the pushrod then turn in the adj nut until all lash is removed. This can be determined by rotating the pushrod while turning the adj nut. When play has been removed, turn the adj nut in one full additional turn (to center the lifter plunger).

so you go 1/2 turn which is 180 degrees? Wipe the cam? Jeez, I didn't even think of that. I did that one time years ago on start up of a new engine. Thanks.
jor

 

[dyeager535]

I won't comment on the pattern of tightening them. I forget too quickly, so I just make sure whatever valve I'm working on the cam is not on a lobe, and adjust. Rotate the engine for the next one, etc.

I *think* what they are talking about for lash is either that the pushrod doesn't have any vertical play, which you'd have to determine by watching the rocker and tip of the pushrod I guess. In any case, that's a pain, and hard to do with the very soft springs of non-pumped up hydraulic lifters. You can get the rockers close by eyeball, but once it looks like the pushrod is going to be in constant contact with the rocker, start spinning the pushrod. The instant you feel ANY resistance to spinning it, you've effectively reached the point you need to give it that extra 1/2 turn, which would TIGHTEN the rocker that much more.

Hydraulic lifters are pretty tolerant of "misadjustment" since they pump up with oil, and the spring seat has some play, but if you tighten up the rocker until you can't spin the pushrod, you've bottomed out the lifter seat, and the springs of the valve are now acting directly against the cam lobe.

In any case, since this motor is already well-broken in, you probably didn't hurt anything. On a new motor that you are trying to break in, that would probably be catastrophic to the cam lobes.

Disclaimer: Valve adjustment with hydraulic engines is a touchy subject, and there are plenty of ways to do it that work other than how I do it. I am only putting here what has worked for me.

 

[jor]

Thanks to everybody for your input. I got it going this morning. As everyone indicated I had set them WAY TOO TIGHT. It's running fine now and finally off the blocks. This has made my wife and the neighbors happy. I half expected to see a little group of them at the foot of my driveway, cheering. I think next time I do this (on my 69 Blazer) I'll pick up some of those clips and try the when-running method. Thanks again.
jor

 

[Busted Knuckles]

Don't rely on the spinning pushrod to put you at zero lash. If the ball at the top of the pushrod is an absolute perfect match for the cup on the pushrod, it'll spin easily when the valve is at full lift. Rattle 'em up and down, you'll feel the distance diminish as you tighten the nut. Once all the rattle is gone, you're at zero. 1/2 to 3/4 turn down from there and you're set. I always like to tighten and loosen until I'm sure I'm at zero, fiddling with it a bit to make sure it's right where the rattle stops completely.
On a big solid roller, the order is different (due to cam deflection from those honker springs), but on a flat tappet or hydraulic roller, I like to start with #1 at TDC on the firing stroke (just check the distributor rotor position to make sure you're not 180* out). Adjust #1. Turn the crank 90*, then go to #8. It'll take two complete crank revolutions but you can follow the entire firing order until you're finished. This way, you don't have to try to remember which pistons/valves are in which location.