Setting valves

Just bought a '72 Pontiac Luxury LeMans with a 350. After work this evening I was giving it a major tuneup, oil change, tranny fluid change, etc. I did a compression check on the engine and came up with one dead cylinder. After popping the valve cover I see one of the rocker arms has come loose and rotated 90 degrees. Flipped it around and was getting ready to tighten it up, but when I went to my Chilton's manual for the specs, I see they're not listed. They show the settings for a RamAir engine and for a 6-cylinder, but not the basic 8-cylinder. Can someone give me the valve lash settings?

Also...are there supposed to be locknuts on these rocker arm nuts? I was able to loosen the nut with one finger...granted, once I set it there SHOULD be sufficient pressure to keep it in place, and I didn't see locknuts on any of the other rocker arms. Do these nuts tend to vibrate loose over time?

Thanks!

Iv'e never had any pontiac 350's. Mostly 389's and 400's, but most pontiac v8's are generly the same. Pontiac rocker arm studs are bottle-necked, meaning there is no specfic setting for the valves. You simple tighten the rocker arm nut until it "bottoms out" or stops. I believe the toque spec on the nut is 25 ftlb. If you find your rocker arm studs are not tappered, you will have to set your lash. Different people set them different ways. Iv'e always set each individual valve per cylinder.
I start with #1 on go right up through. Rotate engine until #1 intake valve just starts to open, exhaust valve will be closed. Tighten rocker arm nut down until there isn't any up and down movement in the pushrod, that will be extremely close to 0 lash. Tighten rocker arm nut 1/4 to1/2 turn. I usually go 1/4 turn. Then continue onto the other valves. This method is quite time consuming, but Iv'e never had any problems when setting my valves this way.

Yes the valves are torque type,meaning you torque the rocker arm nut to a perfered setting.And on pontiac 350's there torqued to 25ftlbs.

I must have seriously screwed up in the past, but I could NEVER get anything NEAR 25 ft-lbs. torque on my '67 GTO 400 cid YS engine rocker arm nuts.

I've seen that spec in repair manuals, read it suggested in many forums, and heard people state in in conversation, but it has never worked for me.

The original reply by Scott Sheeder seems contradictory. At first he suggests the 25 ft-lbs torque, but then talks about the technique that has worked for me in the past - essentially tightening the rocker nut until the pushrod can no longer be twisted between two fingers. Which is it? My personal experience tells me the latter is the only way that works with the 400's (and therefore the 326's, 350's, 455's, ...)

To be safe, I'd recommend tightening the rocker nuts until there's no lash, start the engine with the valve covers off and rocker oil hole covered on each rocker. One-by-one, loosen the nut until it clatters, then tighten it 1/4 to 1/2 turn past the point when the clattering stops. That should do the trick. When I've tried to achieve 25 ft-lbs. of torque with the engine running, it would run like absolute CRAP after torquing one or two rockers. Any more than that and it would stall the engine!

Also, for that '67 motor, I threw out the stock Pontiac lock nuts (3/4 of them had stress fractures at the base), and used Chevy nuts that had the nylon lock ring pressed into the top. They worked great. I had around 15k problem-free miles on the engine before selling it.

I'd really like to know if I'm wrong, or if perhaps I had some odd-ball rocker studs perhaps in that '67 motor, so please don't hesitate to reply.



-Adam
'69 GTO

Forgive me if this is a stupid question, but why are you tightening them with the motor running?

Actually it's the fine-tuning I did while the engine was running. I initially tightened the rocker nuts until I couldn't twist the push rod any longer. Then started the engine and backed off the nut until tapping was heard, then tightened it 1/2 turn beyond when the tapping stopped. It can be messy if you're not deflecting the oil hole in the rocker end, but they sell clip-on deflectors just for that purpose.

I recall that I had 670 heads on that '67 GTO motor. Was it unique that the 25 ft-lbs didn't apply to these heads???



-Adam
'69 GTO

Once you torque the rocker arm nuts to 25 ft.lbs YOUR DONE.You dont have to tighten the nut done with the engine running,unless you have a chevy 350. Tim

I may be doing a cam in my '69 GTO this summer. I'll report back to the group if I have another oddball experience. It would be fantastic if this engine works with the 25 ft-lbs. That would save me a ton of time and effort.



-Adam
'69 GTO

If you guys would read my explanation more closely you will clearly see that I did not contridict myself! Most pontiac heads use the same type rocker arm studs, which mean they are bottle-necked. So you simply tighten the nut down until it stops and then torque to 25ft/lbs ..... If your studs have been changed and they are not tappered then you must set the lash the way I described before. I used the term "what works for me " because different people may set them differently.

I did not say to tighten the nut until you could not twist the pushrod between your fingers, I said to tighten the nut until there wasn't any up and down movement as that would be very close to 0 lash.

Adam your 670 heads from the factory would have had the bottle-necked studs. If you could not torque your rocker arm nuts then somebody had to have changed your rocker arm studs.

To explain myself, when I say most pontiac heads, I use that term because ther is one head I can think of that did not use tappered studs and that I believe is the ram air 5 head, and most pontiac lovers know that this engine was not used in a production model GTO that went to a pontiac dealer.

Believe me, I don't want to give anybody the wrong impression of myself. I do not know everything there is to know about pontiacs, but I have had a number of GTO's, mostly 65 & 66, and have learned quite a bit from personal experience with my cars.