Adjusting Hydralic Valves

[Ray C.]

I am having a problem adjusting hydraulic valves on the base rebuilt 250HP engine. (Stock components) The valves were set cold after engine rebuild. The engine ran fine and there was slight rocker arm chatter. Today we cut an old valve cover so that we could adjust the valves with the engine running. We backed off on the rocker nut until the rocker arm started to chatter. The manual states to the tighten 1/4" turn at a time until 1 complete turn has been completed. The maximum tightness we could achieve on the left bank was 1/4 turn before the engine started to run rough. If we went more than a 1/4 turn and let the engine run for 30 seconds there was no improvement and engine still idled rough. If we backed off on the tightness the engine would idle fine. The right side was even worst. We could not get all the chatter out of the rocker arm with out causing the engine to run poorly. The engine actually ran better and quieter when we set the rocker arms cold. The heads were machined and an engine shop installed all new valves components with hardened seats. The lifters and pushrods are also new. I now plan to start from scratch, readjust the valves cold and then trying with the engine running and hot. What am I failing to do to get the valves adjusted correctly?

As Always,
Thanks for your help!
Ray

[Clem Z.]

Re: Adjusting Hydralic Valves

it sounds like the lifters have beem collaped and this can happen if you install the rockers and push rods on all cylinders and then turn the engine over to set the valves with no oil in the lifters. you should only install the rocker arm and push on the cylinder you are setting when you do the first valve setting. remove the intake manifold and check to see if all the pushrod cups are up against the clips. running the engine should have done that but check and if they all are up against the clips try adjusting them again so the have about .020 between the clip and the push rod cup

[John H.]

Re: Adjusting Hydralic Valves

Unlikely as it may seem, those are exactly the symptoms you'd see if it got solid lifters instead of hydraulic lifters; are you sure they put hydraulics in it? With hydraulics, there should be ZERO clatter from the rockers, and a full turn down from loose shouldn't have the effect you describe (unless they're collapsed as Clem mentioned).

[Ray C.]

Re: Adjusting Hydralic Valves

I checked with the engine parts supplier on the type of lifters provided. I requested original specs on cam, lifters and push rods, but did not specify GM. He stated that they were anti-pump up lifters. This is not what I had requested, but is what I now have in the engine. I called the lifter maker; Comp Cams and they stated that I should set the lifters using the engine cold process. Tighten the rocker arm nut until the pushrod just stops turning and leave at this setting. This should be close to 0 lash. I asked if I set them hot and with the engine running, where should I set them. They said 0 lash, do
not even tighten 1/8 turn and the lifters maybe noisy. Could some one please list the positives or negatives to this type of lifter?

Again, Thanks for your help!!
Ray

[Mike M.]

Re: Adjusting Hydralic Valves

POSSIBLE NEGATIVE ASPECT: IF YOUR INTENT IS TO HAVE IT JUDGED, IT WILL PROBABLY FAIL ITS p.v. IF THE LIFTERS SOUND LIKE SOLIDS WHEN RUNNING. MIKE