rocker sweeps

[legalize420]

im trying to determine the proper pushrod lenght and need some help. from what i have read the sweeps should be narrow and centered. i started with the stock pushrod and the sweep is dead center but its wider than most of the pictures i have seen. its about a 1/4" wide. is that too much? next i went to use my pushrod lenght checker and started out with 6.30. the problem im having is the valve starts to open before i get to the torque spec. am i supposed to be using shims also to determine length. btw, i have ped mount rockers and i am using a modified stock lifter. what should my next step be? should i try the shims. i thought they were more for setting preload when setting up the valvetrain. any suggestions? thanks

 

[R.J.]

Here is a pic of what it should look like. Also this is a great procedure for adjusting the rockers:

This method of adjusting rockers will guarantee that the cam lobe of the cylinder that is being adjusted is at its lowest point.

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…


If the valves start to open when adjusting that is ok, just turn the engine over a few times by hand untill the lifters bleed out.

 

[legalize420]

thanks for the reply. i have ped mount rockers so the procedure is a little bit different for setting preload. from what i have read when checking pushrod lenght you can not use a stock lifter. i modified a stock lifter so it can not depress when spinning the motor over. the pic you posted is what mine looks like with the stock pushrod. i said above about a 1/4" wide but i meant to say its about an 1/8" wide. my concern was other pictures i have seen from other articles and post the sweep is much smaller. you think i will be ok if they look like the pic posted. the reason why i am checking now is i was having alot of valvetrain noise. i always had some noise but it was getting louder than in the past. i noticed some of the valve tips were damaged so i ended up pulling the heads and dropping them off at the machine shop to have new valves installed. i never checked pushrod lenght in the past so i wanted to make sure i have it right this time around. does anyone know if you are supposed to use shims to determine the correct pushrod lenght?