[Baba O'Riley]

Car is a ‘71 Formula I’ve had 30+ years. It’s a YS code 400, original block / heads but recently rebuilt by a longtime local shop.

Four years ago, when the motor was close to rebuild time, I had a rocker arm come loose while driving. It’s on the passenger side – the fourth rocker from the back, fifth from the front. Instead of sitting crosswise to the head the rocker was lying diagonal, and so loose I could move it with my fingers. I bolted it back onto the pushrod and thought that was that.

As I said the motor got a long-block rebuild last year but the other night, the exact same thing happened with the new motor. Same exact rocker. (The rebuilder replaced the pushrods but re-used the rocker arms.)

The weird thing, of course, is that the same thing happened with a tired old motor and then again with a just-rebuilt one. Both times it happened at highway acceleration. Banging noise, loss of power, and this time it damaged the oil dripper on that side – it’s now bent at the front and the front mounting pedestal that bolts the dripper to the head broke at its base.

Some guys on this and other boards say these oil drippers aren’t really necessary, but this is a stock motor and Pontiac must have had these drippers under the valve covers for a reason. Unless you guys say don’t bother replacing it, I’ll hunt down an undamaged one. Thoughts?

After the rebuild I asked the mechanics: does the car need to come back at 500 or 1000 miles for you to re-torque the heads, adjust the valves, and so on? They insisted with the new rebuild kits that’s no longer necessary. Again, your thoughts? What in the valve train could cause this to happen before and after a rebuild?

Thanks in advance to everyone and have a great Christmas.

[b-man]

Original factory bottleneck rocker studs, correct?

I’d be replacing those with new ARP 7/16” straight big block Chevy style studs and either self-locking crimp nuts (enabling you to retain the dripper baffles) or polylock nuts.

People using aftermarket roller rockers can’t use the baffles because they don’t fit with the larger rockers and taller polylock nuts. The baffles weren’t used until the 1965 model year so it’s not like the engine can’t live a long life without them.

During the rebuild I’m thinking the rocker studs probably weren’t removed so that’s why the bad stud causing the issue stayed in the same spot. Your valvetrain will be stronger and more reliable with the ARP studs.

[steve25]

Seems like the basis for your issue is with that head.
Bad stock stud.

I have seen the stock rocker nuts fracture but not come apart from being over torqued.
If this had taken place the 20 ft lb factory setting will not hold.

You have to look for the fractures on the flat side of the, as the problem at times can’t be seen on the other side.

[Half-Inch Stud]

Could be the person or procedure in doing the Lash setting.

I had the bottleneck stubs on me 1st 68 LeMans, and yea some would go off AFTER the cam and lifter swap. Replaced the grooved studs with new press-ins and they all behaved. Soon went to a lifelong set of improvement: 16 Heads, 428, HEI...

[ta man]

Any chance your cam is going flat?? Just a coincidence?

[Half-Inch Stud]

Big guess: "What we have here is a failure to rotate"

[Skip Fix]

Originally Posted by ta man

Any chance your cam is going flat?? Just a coincidence?

My suspect also.

[b-man]

Regarding the chance of the cam lobe going bad, if that particular lifter bore is heavily worn or out of round and not allowing that lifter to rotate how it should that’s a distinct possibility.

If it’s simply the rocker nut loosening then you might have bad stud threads or worn out or cracked stock rocker nuts which were likely reused during the rebuild since they didn’t use new rocker arms.

New aftermarket 7/16” studs and adjusting nuts should have been installed anyway, the stock Pontiac non-adjustable valvetrain isn’t one of the good features of the design.

[Baba O'Riley]

First off, thanks to everyone for sharing your expertise.

Yeah, the fact that the same rocker arm did this before and after a rebuild all but proves those are the original studs, I mean it'd be a one-in-sixteen chance the studs were pulled and the bad one was put back in the same spot. Cam was replaced as part of the rebuild.

So this means pulling studs that haven't been wrenched since Jim Morrison was alive. My nightmare is that one or more of them break... to drill them out the head would have to be pulled to prevent metal shavings from getting down into the head, correct?

[b-man]

The rocker studs will be tight but will come out no problem, I’ve removed plenty from untouched junkyard heads and they all loosened up with no issues.

Just try to use a quality six-point socket when removing them.

[Baba O'Riley]

Okay thanks, will do. Hopefully being soaked in oil all along kept those studs from freezing into the head the way bolts do in components that carry water.

What should the new stud be torqued in at, on a Type 96 head? And the rocker nut, what about that?

[Baba O'Riley]

So I checked the threads on both the stud and the nut with a magnifying glass, and they look very clean, no signs of stripping or cross-threading at all.

Then I put a good six-point socket on the stud, with an 18" ratchet behind it, and tried to loosen it. No go. I didn't completely put all my weight behind it, but I pushed plenty hard. As I said, I don't want it snapping off in there.

I'm going to think about this, where to go from here. It's not a part of the car I want to put a torch on, to heat that bolt! I think my mechanic has this thing that clamps to parts like this and heats them electronically, maybe that would free it.

Merry Christmas, hope everyone has a good feet-up day tomorrow.

-- Dan

[steve25]

Pontiac rocker arm studs should only be torqued down to 75 ft lbs, your cars wheel nut take about the same force to bust free .
A 11/16” impact socket and a half inch breaker bar should make short work of busting it free.

[lust4speed]

As far as torqueing rocker arm studs my '67 service manual says 50 fp and the Wallace chart says 55 fp.

Oil drippers were originally installed because some engines were allowed to idle long periods of time - police cars and taxi cabs come to mind. Unless you plan on attending car shows and letting the engine idle throughout the show, I wouldn't worry about the drippers.

[steve25]

Your correct, my flub!

[Schurkey]

Do we know that this isn't a tight valve guide occasionally seizing, then the rocker flops when the lash becomes insanely large?

[steve25]

Are you seeing any signs like these?
All are signs of weak or failing valve springs.

1) multi rocker contact pattern on the top of the stem because the valve is spinning.

2) valve keeper scuffing .

3) shinny areas on the valve springs.

[67Fbird]

If you are STILL using the original press in 3/8 bottleneck studs....you have a head problem. Anything other than that you have a mechanic problem....or worst case a mechanical problem.

[Baba O'Riley]

These are all possibilities, and plausible ones, but nothing that looks definite. The valve springs are new, as are the rocker balls and valve guides. I can see what looks like socket marks at the base of the rocker studs, and the threads look new, so those might be new as well. They are the same bottleneck type that you typically see on heads from this era. Steve... I'll check the spring there in daylight tomorrow, see if there's any shiny / worn signs on that spring.

[johnta1]

Cam was replaced as part of the rebuild.

Know what cam?

I would do what b-man said in post 2

The stock studs and nuts are made to just bottom out on the taper of stud.
If you have a different valvetrain setup (like a different cam or lifter ball height) that factory adjustment is only good for original setup.

You need an adjustable valvetrain now probably. The stock setup only has one setting. Possibly too loose now. That cylinder probably has a bigger difference than the others but enough to cause the lifter to collapse or something making it too loose?

Anyway easier thing to do and an upgrade studs is always good.

The studs need an impact wrench to make it easy work. Deep well socket also.