stud mount rocker question(s)

[95CobraMike]

Can someone explain to me what lash is on rockers/springs?
i guess while you are at it, if you could explain preloading the springs too...that would all be helpful to me....thanks

im trying to adjust my rockers so they are on right...

 

[final5-0]

The range of pre load can be from zero to 3/4 of a turn.

Strip only will be on the less and street will be more.

More is usually quieter.

Pre load is the amount you go beyond the point of no clearance between the pr & lifter cup.

Grady

 

[Zero Signal]

When you adjust your rockers (aka setting preload), the pushrod pushes on the top piece of the lifter. It compresses a small spring inside the lifter and will push out any oil left inside the lifter body (slowly). When you adjust the preload, you are determining how far down the pushrod sinks into the lifter (say .020-.060").

When you start the car and the oil pressure builds up, oil fills the lifter back up and pushes the seat against the pushrod. It keeps that force on the pushrod at all times to keep the valvetrain tight and noise free.

Most people go with the 1/2 turn or so methods. I didn't like that so I picked up a dial indicator to measure the preload exactly.

 

[95CobraMike]

so if i were to put the stud into the head, slide the rocker over the stud, put the nut thing on finger tight, so the p.r. is in tight against the rocker and the lifter, then turn the nut 1/2 to 3/4 of a turn tighter... this is how you do it?

(this is all assuming the lifter is completely down)

 

[95CobraMike]

what about lash?

 

[R.J.]

I really like the method below because it makes it really easy to know when EVERY cylinders cam lobes are at their lowest point, not just #1(because #1 TDC is easy to find). This is the key to getting a perfect lifter preload. This method make the entire job really fun and easy.


With the piston at TDC with both valves in the closed position, do the following:

The first thing you want to do is verify zero valve lash. The best way to do this is to wiggle the push rod up & down as you tighten the rocker arm nut. At the point where the push rod no longer moves up & down, That is zero lash. You now have a starting point for verifying “true” zero lash & the lifter pre-load.

When you adjust the valves you are setting the lifter pre-load, Pre-load is the amount of distance the push rod seat (or “cup”) moves away from the retaining clip.

To set true zero lash & the lifter pre-load, We are going to follow the “EO / IC” procedure.

What is “EO / IC?

EO, is Exhaust Opening; IC, is Intake Closing.

We have the piston at TDC (Both valves are in the closed position), Rotate the engine in the normal direction of rotation (clockwise, if you are facing the front of the engine).
You will see the exhaust valve just starting to open, stop rotating the engine & back off the intake rocker arm.(You are going to back off the rocker arm & re-verify for true zero lash, As you are now positively on the base circle of the camshaft whereas the previous lash adjustment was just a pretty close ballpark guess.) You will once again wiggle the push rod up & down as you tighten the rocker arm nut. When all up & down movement is gone, tighten the rocker arm nut ½ turn, tighten the hex head set screw until it bottoms out on the rocker stud, tighten the rocker arm nut ¼ additional turn. You have now set the lifter pre-load at .045”.

Rotate the engine, You will see the exhaust valve fully open & then close. Watching the intake valve that you just set, You will see it open, You want to keep rotating the engine until it fully opens & then starts to close. When it is almost closed, stop rotating the engine. Set the exhaust valve the same way you did the intake valve.

Move onto the next cylinder in the firing order…

 

[95CobraMike]

thank you sir!! thats the kind of explination i was looking for!

 

[R.J.]

Glad I could help

 

[Methodical]

I really like the method below because it makes it really easy to know when EVERY cylinders cam lobes are at their lowest point, not just #1(because #1 TDC is easy to find). This is the key to getting a perfect lifter preload. This method make the entire job really fun and easy.


With the piston at TDC with both valves in the closed position, do the following:

The first thing you want to do is verify zero valve lash. The best way to do this is to wiggle the push rod up & down as you tighten the rocker arm nut. At the point where the push rod no longer moves up & down, That is zero lash. You now have a starting point for verifying “true” zero lash & the lifter pre-load.

When you adjust the valves you are setting the lifter pre-load, Pre-load is the amount of distance the push rod seat (or “cup”) moves away from the retaining clip.

To set true zero lash & the lifter pre-load, We are going to follow the “EO / IC” procedure.

What is “EO / IC?

EO, is Exhaust Opening; IC, is Intake Closing.

We have the piston at TDC (Both valves are in the closed position), Rotate the engine in the normal direction of rotation (clockwise, if you are facing the front of the engine).
You will see the exhaust valve just starting to open, stop rotating the engine & back off the intake rocker arm.(You are going to back off the rocker arm & re-verify for true zero lash, As you are now positively on the base circle of the camshaft whereas the previous lash adjustment was just a pretty close ballpark guess.) You will once again wiggle the push rod up & down as you tighten the rocker arm nut. When all up & down movement is gone, tighten the rocker arm nut ½ turn, tighten the hex head set screw until it bottoms out on the rocker stud, tighten the rocker arm nut ¼ additional turn. You have now set the lifter pre-load at .045”.

Rotate the engine, You will see the exhaust valve fully open & then close. Watching the intake valve that you just set, You will see it open, You want to keep rotating the engine until it fully opens & then starts to close. When it is almost closed, stop rotating the engine. Set the exhaust valve the same way you did the intake valve.

Move onto the next cylinder in the firing order…

Just as another option to set 0 lash, you can also twist the pushrod while tightening the rocker arm nut until you feel a drag on the pushrod.

Peace