93 LT1 vett, have had a valve/lifter noise for a couple of weeks now. Took valve covers off today and just wiggled the rockers that were on the cam base, there is a lot of play, you can jiggle the rocker back and forth very easily but not up and down, is that normal?

The FSM says to adjust valves; tighten rocker nut until lash is gone then go another full turn, is that a good recommendation for a stock motor? What about 3/4 turn?

Any comments appreciated.

 

It is normal for the rockers to have some side to side play with the cam on base circle. If you go 3/4 turn, your preload will be less and the valvetrain might be noisier. Might want to readjust all the rockers since you have the covers off just in case one of the adjusting nuts has backed off.

 

Not sure how normal that is; can you twirl the pushrod between thumb & finger?
If so they need adjustment.

 

yes you can twirl the pushrod on just about all the rockers, a couple are tight enough not to turn very easily but most are very easy to rotate in your fingers!?? I hope to get the adjusted today just not sure which method to try, while motor running or the old FSM way of rotating the motor to the #1 TDC adjusting then rotate 360 and do the rest. Thanks for the comments

 

Noise is trying to tell you something. It's saying "Somethings NOT RIGHT". Ignore it at you and your engine's peril.

I'm not specifically familiar with the FSM for your year, but the one for my 96 LT1 gives a preload range - ONE FULL TURN (+/- 1/4 TURN) Re-read yours and see if yours says something similar.

I've come to conclude that the preload adjustment depends on the lifters being used. Comp's lifters call for a different spec than GMs, but they're Comp's lifters. ISKY's and other may be different, so I let the lifters I'm running determine the preload setting. Their engineers know what works best.

I set my GM lifters and my son's GM lifters at 3/4 turn with no problem in many thousands of miles. I sincerely believe that any setting within spec up to ONE AND 1/4 TURN of preload would work equally as well. Crane's extensive testing showed there's NO downside to running the factory preload setting.

My advice is don't play the spin the pushrod game. Results are most often confusing and only lead to even more problems. Even CompCams has now moved away from their previously recommended "spin the push rod until slight resistance is felt" because what's slight to one person isn't to another. Guys have ended up tightening up the adjusting nut until the pushrod was COMPLETELY BOTTOMED OUT in the lifter. That's an example of how confusing that procedure can be.

Moving the rocker arm side to side isn't a proper test either. With the lifter riding on the base circle of the cam lobe the rocker is capable of being moved. That's normal. Up or Down NO!

Merely cranking in more turn(s) on the suspect rocker isn't the way either. If it's suspect, the correct way is to release all the preload and start over with the lifter on the base circle of the lobe. IC/EO method is the widely preferred method even though there are those who continue to cling to the "Old School", yet out-dated method.

If after doing that and you still have a problem it's time to dive deeper to find the cause. A couple of guys have recently posted they found their lifter rollers (cam end) were shot after hearing valve train ticking sounds.

Best to catch this kind of stuff early.

Jake

 

You know, I use to sort of get bent out of shape when I'd read "adjust(ing) valves" on a hydraulic cammed engine when, what you're doing is adjusting lifter preload. But I'm getting over it, LOL

Jake

 

Jake thanks for a little grace, I am trying to adjust the lifters but turning the nut on the rocker!!!??? haha, anyway I just took it out for a drive, ran great, no noise, smooth idle but when I got home and it was hot there is a definite miss at idle. I think it goes away above that but not sure (seems to run fine under WOT and cruise). I wonder if I got preload too tight on one lifter? By the way the FSM says "back off rocker arm nut until lash is felt in pushrod assy.. then tighten nut until all lash is removed. zero lash can be felt by rotating pushrod assy. between thumb and forefinger until there is no more movement, when all free play is removed, tighten rocker arm nut one additional turn? It seemed obvious to me when the pushrod was tight.
I tried the adjusting method with the motor running but when I backed off the nut until I hear tapping noise and then tightened it a full turn, the engine almost died, it bogged down really bad, scared me so I stopped and did the old method from the FSM.
Any comments?

 

When you were running the motor and backed off on the adjusting nut until you heard the lifter clacking, there was no preload on the lifter and the lifter was pumped up. When you cranked the nut down, the lifter did not have enough time to compress. Valves or pushrods can be bent doing this if the valve and piston contact.

 

so what should i have done differently, turn the nut more slowly, or is this adjusting with the motor running a bad idea altogether?

 

Turn the nut more slowly

 

Right. If you choose to use that procedure just give the lifter more time to adjust to the new preload setting as you tighten the nut. The engine will often stumble, but quickly smooth out.

Jake

 

Naw, it's not you. I've read this same thing in manuals where the author writes about "adjust(ing) the VALVES. My issue is/was that when dealing with hydraulic cams you'd be adjusting lifter preload but on mechanical cams you'd be adjusting valve lash. Just seems so inexact to refer to the procedures as etc.

One thing I still don't have a handle on is why it use (still?) bugs me. Maybe something in my DNA, LOL

One other point to consider is most of the FSM's/manuals we reference - which includes me and mine - were written a decade - (and often more) - ago. I'll have to do a check on my three FSMs to see when they were last revised, but I suspect some of the info they contain date back to their original printing date.

Jake

 

Ok now I am really going to look stupid but here goes. The noise is NOT lifter noise, it is fuel injector noise! I got the ole screw driver out and put it on the heads, rocker studs and could not hear the clicking I heard just listening to the motor run. Then I put the screw driver on the injectors and that's where the noise is coming from. Now I can see it is too fast of a clicking for a valve noise. Last fall I bought new Bosch injectors from Jon here on the forum, at that time it really improved performance but since this spring I have
had this miss from idle up to 1000rpm, I think it goes away after that but can't tell for sure. I unplugged each injector at idle and each time the motor bogged down, I don't think I can find an intermittent miss that way but was worth a try. Now I ordered new Delphi o2 sensors, I am getting no codes but I know they can be "slow" with out throwing a code, we will see if that helps unless anybody has other suggestions.
Sometimes I hear of people using a tech reader of some kind to check stuff on the motor, does any one know what reader this is or where to get one? Is it something a novice can use? Thanks
PS; Last night I went out for a 30min drive, started up - ran fine, no miss, drove 15 min, motor fully warmed up, stopped at light, miss was back, got home and sat in driveway, miss there for sure. Shut motor off for 15 - 20 min, and started back up, miss gone, drove it into the garage, let it idle for 5 - 10 min, no miss ??

 

I'd first check the easiest and most obvious stuff: plugs and wires. Another guy just recently went round after round trying to track down his backfire and posted a LOT on what he hbad checked. Turned out to be nothing more than a bad plug wire that crumbled in his hand as he tried to remove it.

So, sometimes it's the simplest things.

I'd next check for a crack in the porcelain on a plug - check the color while you're at it.

You can buy an expensive, easy to use noid light at most auto parts stores to check the injectors.

Run the engine is a REALLY dark environment and look for any arching spark.

Make sure no plug wire is running too close to the coil or the ignition control module.

Keep us posted.

Jake