Let me be clear about this, I am a novice. I adjusted the valves on the #8, #6 & #4 cylinders today because I was hearing a clicking noise from the right rear of the engine under the valve cover. I have listed details on how I did the valve job below. However, my question is this, “ if I push very hard against the side of the (stock) rocker arm when the pushrod is at its lowest point I can make the rocker arm come off of the spring.” Is that normal?

The engine seems to run OK, but I haven’t taken it out of the garage yet because of this question.

The engine is a ’93 LT-1 that I rebuilt last summer. I have about 9,000 miles on the rebuild.

I used Jake Cameron’s method for setting the valves, ie., when the exhaust pushrod of a cylinder is just starting to come up, the intake is on its base circle, and when the intake pushrod is almost down, the exhaust is on its base circle.

I measured these movements with a magnetic mounted indicator dial. (Note: Magnet doesn’t work on aluminum engine). Tricky to do, but it works.

Not having a good “feel” when the pushrod is at zero lash, I used a .0015” feeler gauge between the spring and the back of the rocker arm to determine when the pushrod had actually touched the rocker arm.

I also made sure that the socket wrench was not all of the way down on the rocker arm adjustment nut as I did these measurements. After zero lash I added ¾ of a turn on the adjustment nut.

I am an engineer, not a mechanic. I don’t have experience on this task, thus I don’t have a “feel” for the task; that’s why I used so many tools to measure rather than feel the zero lash, and pushrod position.

Thanks,

Larry…

 

Larry,

It is not normal to be able to remove a rocker off the valve stem without loosening anything. It is normal for correctly adjusted rocker arms to feel a bit loose (side to side but not up and down) between run cycles on hydrolic lifters aplications. When the engine is running oil pressure builds and takes the slop/noise out of the assembly. When the engine is off and oil pressure within the lifter is not present and the lifter is on the base circle portion of the cam lobe only a small spring (inside the lifter) holds pressure against the pushrod. Below is a picture of the interals of a non-roller hydrolic lifter just so you get the idea of what is going on inside the lifter....pretty much the same thing as a roller hydrolic lifter minus the roller on the bottom.

The FSM (Factory Service Manual) books will tell you to do "1 full" turn of preload after finding zero lash. This is always a hot topic -opinions vary on this preload methodology - depending on the method used to find zero lash (bump pushrod up & down, spin the pushrod or use a feeler gauge) this may vary the amount of preload you want to apply. Find zero lash and adjust each rocker nut one time do not spin the engine 180 or 360 and try to take the slop out of the rocker(s) again....this will cause the valves adjustments to be too tight. Too tight - usually you can hear it pop a little in the exaust/intake. Too loose - the valve train will make a hollowish (metal to metal) tapping sound. Of course these noise will be louder the further your further off from the correct preload.

Personally-I feel 1 full turn of preload is too much and I have success using less preload. I use the spin the pushrod apporach and apply 1/4 -1/2 turn amounts of preload depending on the type (roller or stamped) of rocker used. But again opinions vary.

I have not used Jake Cameron’s method personally but it is very sound apporach and pretty close to how you'd adjust a solid (non hydrolic) lifter application.

If your remember how much more/less preload you just did just the other day I'd put the preload of 4, 6 & 8 back where they were before. If your sure you found the proper zero lash before applying the same amount of 3/4 turns of preload to each the first time you adjusted them after the rebuild you can always loosen or tighten each rocker nut in 1/4 turn intervals to see if you can quiet down the valve train.

 

-OR- just adjust them while the car is running. Loosen until you hear a very slight clack, then tighten just enough to remove the clack, then give it another half turn.

After seeing 100 different methods from here and everywhere else I decided to do them with the car running. I expected a deluge of oil but I don't think a drop was lost.

Just be VERY careful to not drop anything!

 

[QUOTE=engle1147;1574630751]Larry,

It is not normal to be able to remove a rocker off the valve stem without loosening anything. QUOTE]


I was able to move the rocker off of the valve spring, not the pushrod. Does that make a difference?

 

no difference. Rocker should not be able to moved off the valve stem or pushrod without tools....if you can do it by hand then it has the potential to do it while running as well. Did you go on with self aligning rockers or are you running guide plates? Sounds like your running non self aligning stuff.

 

These are the stock rockers, thus I think they are self aligning. They little raised edges on both sides. The top of the valve rides between these two ridges.

I don't want to mis-lead here. The cam was at its lowest spot and I had to shove very hard to knock the rocker off of the valve stem. It was a pita getting it back on.

 

I think if the lifter was on the camshafts base circle, if the rocker is rotated hard enough, the raised edges of the self aligning rockers can ride up and over the valve stem. The pushrod will depress into the lifter just a little bit with some force and allow enough lash for this to happen. In the real world, there is not much lateral force for this to happen. I wouldn't worry about it.

 

Thank you everyone for your input.

I took the Vette out for a spin. My valve noise is gone, and the putt-putt sound is gone.

I drove it around the neighborhood, then on a busy street and then on the xway. Highest RPM I could do without upsetting the local police department was 4200. The car ran fine, and the valve stems did not jump out from under the rockers.

I believe it is working properly.

Once again, I have to thank the Corvette Forum and all of the people that helped me in this project. At this rate I can keep this '93 Vette running until we run out of oil... which may be next month at the rate BP is going.