My engine has accumulated a little over 1000 miles since it was rebuilt. I now feel it's time to check the valve lash. It is a hydraulic flat tappet cam,and I know this might not be necessary, but I just want some peace of mind knowing that my valves are lashed properly. My engine has full roller rockers with the we adjustable lock nuts. I'm not familiar with adjustable valve train, so could someone please give me a run down of how I should properly set the lash, and tighten the nuts?

I know with a hyd. cam on the street, the lash should be set at zero, but is there any more power to be had by changing the lash? I've heard of it working on solid cams, but I'm not sure if would just pre-load the lifter. Any help would be great. Thanx graemlins/thumbsup.gif

Set 'em and leave 'em alone! If it was done right when the motor was built the preload should be fine now. After all they set them at the factory and they get run for a couple hundred thousand miles without adjustment, right?

If you have reason to believe yours need adjusting, then I think you will find that most hydraulic cam/lifter combos will work well with 1/2 turn of preload. Just find zero lash and tighten another half turn. You can find zero lash by loosening the adjusting nut then twisting the pushrod between your fingers while slowly tightening the nut until a slight resistance is felt.

I agree 100% with Eric. Unless they are making noise or you hear popping (too tight) they are probably just fine. I set mine the same way as Eric described. I never touch them again, unless I have had to disassemble for some reason. I don't know of any benefit in adjusting the preload. All the hyd. cams I have run have always said 1/4 - 3/4 turn preload.

If you're not having any problems theres probably no reason to do it but then again it won't hurt anything to check (as long as you do it right).

There are 2 ways you can go about it, I'd recommend this method: Start the car up and let it run for a few minutes to get some-what warm, take off the valve cover and, with the motor still running, slowly and gently back off each rocker until it starts ticking. be SURE that you don't apply any downward force on the nut! Once it starts ticking slowly tighten it until it stops. Do this on every rocker and then turn the motor off. Now, go ahead and tighten each rocker 1/2 a turn. From the factory GM usually goes a full turn to ensure they won't need servicing during their warrenty periods but thats unneccesary. It might be a good idea to get a peice of cardboard to sheild all the oil that might be splashing around while you're doing this also.

Second method would be doing it while the motor isn't running (much like a solid cam). This takes a little practice to get right but is much easier for me since my car is very loud, shakey and splashes a crapload of oil everywhere:

With the motor off, turn it over either with a remote starter switch or by hand at the crankshaft. Might be a great idea to remove the spark plugs so it turns over easier. Loosen all the rockers so there is a good amoount of slack in them to allow the lifters to bleed down. Slowly turn the motor over and watch a certain cylinder. When the intake valve of a cylinder just closes, adjust the exhaust valve for that cylinder. Now when the exhaust valve just starts to close, adjust the intake valve. You adjust them by slowly tightening the rocker until there is no play in the pushrod - wiggle the pushrod up and down. Remember! NO DOWNWARD FORCE. Turn the rocker nut a slight amount and then take the socket off the nut THEN check for slack between the pushrod and rocker. Even the weight of the socket will screw up the adjustment. Move onto the next cylinder. Once all are adjusted, tighten them half a turn. I don't recommend this to someone who doesn't have a lot of experience because its easy to screw up but its a lot easier for me.

I would adjust them with the car running. Use an old tall valve cover with the top cut off. Don't rev up the engine while doing the adjustment. Loosen one nut until you hear clacking, tighten it until it just goes quiet, then give it 1/2 turn on the wrench. I always do 1/4 past zero but many people prefer more. Do them one at a time and finish each one before you move on.

Thanks guys, I think I'm just gonna leave them alone. Don't fix it if it ain't broke...right?!? Just one question though out of curiosity. On the adjusting nut, there's this small allen head screw, what's that for? Does that lock the adjusting nut in place or what? It's a pretty cool design. Anyway thanks again. graemlins/thumbsup.gif

You have what is often refered to as poly locks. You need to back the allen screw out a few turns so they don't interfere with the valve adjustment while you are setting the valves. When the valves are adjusted down about 1/8 turn looser than where you want them, snug the allen screw down while holding the main nut with a wrench, then finish tightening the main nut the last 1/8 of a turn. The 1/8 turn is not an exact figure, but it works well with hydraulics...it takes a bit more finagling with solids. FWIW, I use 1/2 turn preload on hydraulics. I also always double check hydraulic valve settings after a few hundred miles just for peace of mind.