Copying and pasting this question I posted on the thirdgen board. This is for my 1989 Formula 350 but since it is the same l98 as the Corvette's (except aluminum heads) I thought I'd ask it here.

I know this has been gone over to death but I have to ask about it once again. I have installed some 1.6 roller tip rockers and thought I was doing the adjustment correctly but the engine idles high (1.5k) and misses when I accelerate......bad miss.
The method I was using was turning the engine and when the #1 exhaust pushrod started to push up against the rocker I stopped and adjusted the #1 intake rocker by tightening the nut until I felt resistance in the pushrod and then added another 1/2 turn of the wrench before tightening up the allen lock. Then rotate the engine again until the #1 intake pushrod pushes up and makes the rocker press down on the spring then just before the pushrod goes all the way back down(rocker just about to stop pressing the spring) I adjusted the exhaust rocker the same as the intake.
DO I have a reading comprehension problem and screwed up the instructions or is there something else I am missing???
Thanks

 

I would to see if you left a vacuum hose off somewhere. The large one that goes from the PCV valve hose to the driver's side of the intake?

 

several years ago, i adjusted the valves in my 85, and had major issues. now, i have adjusted valves for damn near 40 years, but for some reason, the #1 cylinder was giving me fits. three times i adjusted the #1 cylinder too tight, and the thing ran like crap - valves never fully closed. drove me nuts, because i never gave it a thought that the valve adjustment was an issue. seems like the "rotate the pushrod until resistance is felt" was the problem - at least on the #1 cylinder. after giving this a little thought, i readjusted the valves a little different.

for the adjusting sequence i pretty much followed the FSM - so with the engine in the #1 firing position, or TDC, adjust the following:

exhaust -- 1, 3, 4, 8
intake -- 1, 2, 5, 7

now here's what i did for valve adjustment: using a .0015" feeler gauge, between the rocker arm and valve stem, slowly tighten the adjusting nut until the feeler gauge "grabs". at that point, you should be within .001" of zero lash. then adjust the nut 1/2 turn. this method seems a little more exact, or precise than the "rotate the push rod while turning the adjusting nut" method, and should result in a more even adjustment across the board..

now, rotate the crank 1 revolution or 360 degrees, and adjust the following:

exhaust -- 2, 5, 6, 7
intake -- 3, 4, 6, 8

the 85 ran like a champ. several other forum members have used this method with success. give it a try...

 

A testament to Joe C's method. I have also been adjusting valves the old GM way of spinning the rod until you felt resistance for 40+ years. This worked most of the time. When I installed the ZZ4 into the Corvette there were several valves that were very difficult to get my fingers on the rods because of the Roller Rockets and the SuperRam. I tried Joe's method of using a feeler gauge and it worked better than anything I have done in the past.

Turning the crank until you line up the timing mark and adjusting 1/2 the valves and then turning the crank 360 degrees is the standard GM method and works well unless you have a wild cam.

 

Everything is stock except for the new rockers I installed.
Thanks for the vacuum reminder. I had disconnected the line from the purge valve to the throttle body. DOH! Idle issue resolved.
Took it for a drive tonight after I found that but it is knocking when I really hit the gas. Sounds and responds awful. I guess I will give the feeler gauge method a try or just redo them until there is no play up and down from the pushrod then turn another 1/2 turn. SOmething that sounds so easy can always end up being a complete PITA.

 

The best luck I've had adjusting the valves is to do it with the engine running. I just tighten until the valve shuts up and go anther half turn. Although this works perfect every time it kinda sucks *** as oil is leaking on the exhaust making a smoky mess.

 

I'll drive it or tow it to a shop before I go there. That just sounds like a complete mess.

 

 

It's not a mess at all if you use a little common sense. Use cardboard like in this video will make no mess at all. Just make sure the cardboard is down in the head so the oil will drain back to the motor. Get the motor up to operating temp and have at it. When the lifter quits tapping turn 1/2 turn more and tighten it down. Works great!

 

For megtom2. The mess can be managed. You can buy clips that divert the oil back onto the heads. Of course when I tried them I set the car on fire. OR you can get an old valve cover cut a slot from the top to access the valves for adjustment. Works well with no fuss , mess or bother. I am going to try Joe C's method on the 383 however. Sounds neat.

 

Yep, you did it correctly and didn't mis anything. The cause of your problem lies elsewhere.

I see you found the vacuum leak but the "knocking" doesn't seem like a valve train issue, which is usually described a "ticking", "tapping", etc. "Knocking" is usually more related to rod bearings.

Jake

My son, Ryan M. Cameron, graduated from West Point on 22 May 2010! He was commissioned as a 2nd Lieutenant and I pinned on his first pair of "Butter Bars" PROUDEST DAY OF MY LIFE!!

 

I'm going to pull the covers again and just tighten the nut until the pushrod just spins but no up and down movement. The only thing I can think of is that they are a little too tight. Once they don't move up and down I'll go with another 1/4 to 1/2 turn.
My guess is they are a bit too tight and are keeping valves open when they are supposed to be closed.......but that is a novice guess since the engine ran fine before I did the rockers.

 

Re-adjusted yesterday and it idles great but when I hit the gas hard to go it is still pinging. Has more power now but it is pinging. I guess maybe I'll go through it one more time and see what happens if I loosen them a little more. No racket at all during idle. It sounds great.

 

Check the timing. I doubt it's the valve adjustment.

 

I did that and advanced it a little and it seemed to help. Still pinging though. Only does it at WOT under load. Driving me crazy.

 

If its pinging more timing is the wrong answer.. retard the timing or look at the routing of your vac advance.. you may be running full vacuum when Ported is called for.. Pinging at WOT has nothing to do with valve adjustment.

In short I highly recommend a timing light and check your specs and vacuum.

 

What cam do you have in there?

 

Stock cam. Hate to sound stupid but if the damper mark is getting lit up before the zero mark on the timing mark is that advancing or retarding? My guesstimate was advancing but guesstimates can be wrong.
It definitely knocks under WOT. I'll check all vacuum hoses and reset the timing some more and maybe luck into a fix.

 

I have now gone through the ignition system and it is working as it should. It still makes a racket when I hit the pedal. It does ok if I just nurse it up and will go 50 mph no problem but if I hit the gas it makes the racket.
Looks like I need to go back in and readjust the rockers again. I'm guessing they are too tight but any help at this point would be greatly appreciated.

 

If you decide to adjust lifter preload again, remember this: When dealing with the exhaust, DON'T assume that just as soon as you begin to turn the engine over and the exhaust lifter immediately begins to move UP that you should stop.

The exhaust lifter could ALREADY BE ON THE RAMP and if it is, that'll give you a false reading. So TURN THE ENGINE until the exhaust lifter/pushrod is/are completely down (on the base circle of the lobe and NOT moving). Continue to turn the engine until that lifter JUST BEGINS TO MOVE up -that's when you stop.

This has tripped up a few guys in the past.

BTW, stand directly in front of the engine, when the damper timing mark is on the right side of ZERO (TDC) on the timing tab that's RETARD; on the left side is ADVANCE.

Hope this helps.

Jake

My son, Ryan M. Cameron, graduated from West Point on 22 May 2010! He was commissioned as a 2nd Lieutenant and I pinned on his first pair of "Butter Bars" PROUDEST DAY OF MY LIFE!!