Bad engine noise/rattle

My engine sounds TERRIBLE at idle. There is a rattling on the top end somewhere. I've had it off the road and uninsured for the last year or two. Noise goes away at about 1200-1500 rpm.

It will start fine, and I try to run it (idling) every month or so.

This evening I was tinkering with it and decided to take the valve covers off. The passenger side gasket was slightly exposed anyways. I started with the driver's side (easier) and the gasket was good. I tried tightening the 16mm bolt in the center of the rockers. I hope I didn't mess anything up be messing with these. I was able to tighten them all about 1/8 to 1/4 of a turn. I could have tightened them more, but I didn't want to screw it up. I only did a little to see if there was any improvement.
There was. So I did the other side too. I will get a new gasket set tomorrow as the pass side was damaged. After I tightened the rocker bolts on that side too and re-installed the cover (minus the gasket), I started the engine and it was quiet!

Will this adjustment damage the engine? Is it okay to run it now or should I give up and swap motors?

Thanks guys.

Steve

If you overtighten the rocker arms you can bend valves or cause compression problems.

On the oldskool stuff I'd leave the valve cover off put cardboard around the bottom edge to keep oil in the engine, turn the car on and then loosen each rocker till it chattered and then retighten until no noise was heard.

On an lt1 there might be torque specs that are extremely specific like : Xxx in lbs + 90* or something. I don't have a manual to look at right at the moment.

What happens is your compressing your lifters
You could tighten them more & the lifter would compress more.
Dont do it though
The trick is loosening them (to let the liften expand), then slowly tighten until the pushrod touches the roclker with no gap (=0 lash)
Its easier said then done
If you have some miles on the valvetrain & tightening only 1/8 or 1/4 stopped the noise....your good
Dont go further unless you loosen & start again
Hope I read your ? properly

As long as you didn't go more than 1/8 or 1/4 turn, you'll probably be ok. If you really want to redo it, like Indigo said, doing it running is easiest. Back it off til it makes noise, tighten it til it's quiet, then another 1/4 turn and you're good.

Thanks guys.

The car had 280,000+ miles on it. I'm going to replace the valve cover gasket today, then run it and see how it sounds... though only up and down my 200' driveway. until I get it road-worthy.

over the years the lifters build up varnish inside,.after it sits for a while they bleed down , the cup gets caught in the varnish where it never usually rides,.

In the future,.
If you,re doing a start up just to keep the battery good,. keep the rpms up for a few of minutes,.
2g's or so,. its better for it than just idling,. (just wedge a screwdriver in the throttle stop,.

a long term shut down is best done,. if you remove the battery and tend to it out side the car,.
leave the motor be,.

starting up a motor and letting it idle, over and over again,. is the worse thing for the motor,.


Nick