Ok, the other day I started noticing a tap tap tap sound coming from the engine. Sounded just like a loose rocker. So last night I took off the valve cover and attempted to fix the problem. I've narrowed it down to the #8 intake rocker. When I checked the rocker with the engine off it didn't seem loose. So I started the engine and attempted to adjust it that way. Nothing worked, it's still there. Now, the weird part ... the reason I know it's the #8 intake rocker is because when I have the engine running and I put the socket on the bolt, it quits the tapping sound. That's just with the socket sitting on it, not turning or anything. As soon as I take the socket off, it starts again. At first I thought it was a stuck lifter but the rocker arm is moving, indicating to me that the lifter is still moving. I pulled the push rod and looked at it and it seems fine as well. I'm really stumped on this one. The rocker arm isn't loose, the lifter doesn't appear to be stuck, and the push rod isn't bent but I still have this tapping sound ... which goes away when a socket is placed on the nut.

If anybody even has a clue as to what it going on, please let me know ASAP. Thanks!

 

Sounds like you have a wiped out rocker ball. If you could slow the tap down, it would be a squeeeek. The extra mass of the socket prevents the rocker stud from vibrating along with the scraping rocker and ball, so it stifles the noise (or at least most of it), but not the problem itself.

This is a typical cause of "mystery lifter noise", that's not created by the lifter at all of course. People blame this sort of thing on "collapsed lifters" (never actually seen such a thing) and stuff like that. It's amazing how many parts of the valve train can make noise.... I have a valve spring on my motor right now that makes a noise; while I was building it, as I turned the motor to adjust the valves, I heard a little faint "skreeeeekkkk" kind of noise sort of like a door hinge as that one valve operated, and sure enough, it makes what sounds like a faint little tapping sound now sometimes..... probably the inner spring rubbing the damper or something.

Anyway, take the rocker offand look at it, I'll bet the ball seat and the ball both have deep score marks in one place because the ball hasn't been turning inside the rocker. If so, they're fornicated, and you need at least one new rocker.

 

And when you remove that rocker and pivot ball, take a close look at the rocker stud with a good lamp. Check the line of varnish at the base of the stud to make sure the stud is not being pushed out of the head.

If this is a stock '86 LB9, and you have a trashed rocker, your options are to install a stock replacement rocker, or better aftermarket rocker. Heavy-duty stamped rockers with roller tips and a 1.6:1 ratio will not only reduce tip friction, but will help get just a little more out of your anemic factory cam. There are no interference, clearance, or loading issues with those rockers, and the heavy duty rockers provide a more accurate ratio with less flexing.

I installed Crane roller tips on my '86 with no problems (except the installation labor). A full set is only about $110.00, with new nuts and pivot *****. Since you already have the more difficult rocker cover removed (the right side and #8 are the WORST) the installation will be fairly easy and you'll get to inspect all the other rockers - which may be in a similar condition. Buy yourself a set as an early holiday gift, and get those old, scuffed rockers out of there.

 

Ok, I did forget to mention that these are Comp Cams 1.52 roller tip rockers. I installed them with the new 355 last November but they had a few miles on them already when I bought them.

So I need to replace at least that one roller rocker then huh? Next question ... what's the potential consequences of continuing to run this one on there until I can either get a new one or a new set?? Could be a month or so...

 

If you have relatively new Comp rollers, you might want to check to make sure the pivots are truly damaged or if you are pulling a rocker stud out. Don't order up any new parts just yet.

 

I have this bad feeling that it's the rocker stud pulling out. Would be my luck and I don't have the time (with 2 jobs) to pull the head off and take it to have it pressed back in.

 

86,

You never want to press a stud back into position. For next to nothing in cost ($30 at most) and maybe a couple hours of your labor, you can install a complete set of screwed studs in your heads. If you discover that the studs are pulling, you can check this file for easy instructions - no head removal: Screwed Rocker Stud Replacement.pdf

You'll need Adobe Acrobat Reader to open/print the file.

 

Check the valvespring too. I had a simliar experience that stumped me for a while until the spring broke completely.

Pete Cento
84Z28

 

If it is the rocker stud you maybe able to press the stud back in and roll pin the stud in place. I think F-BIRD88 has done this and he said it work rather well and the roll pins are a few cents each plus the cost of a drill bit.

 

Check the rocker arm stud itself. Quite often they get notches in them where the rocker arm ball is, and the ball hangs up on the notch and causes problems.

 

...and new SCREWED studs would resolve that. Pinning is O.K., but if the stud is already moving in the stud boss in the head, you don't want it hammering around in there elongating the hole and ruining the head.