mcox8051

New problem today with my '96 Grand Sport or maybe the old problem has gotten worse? I'm still getting opinions on the clashing noise on startup. Bill at ZR51 Performance says that if it were the clutch fork scraping it would do it every time I shift ...today I took the car for a spin and all was well for about 25 miles. Car runs great and quick but never tached it over 4500 rpm, I don't drive hard, just cruise around. Started hearing a ticking, like a lifter or something, it started running rough, limped home, popped the hood and saw a valve cover bolt moving on the right side! I knew this was not good. Removed the cover. I'm not an engine expert but have tinkered a little, so I don't know whether its intake or exhaust, but the 4th rocker arm from the rear was off the valve and had broken off the spacer for the valve cover bolt. Luckily I was able to remove the broken threads. The rocker is damaged. The two-piece keys were laying in the head. Other than the damage to the roller rocker, everything looks straight. The rocker arm bolt was tight. I was wondering if anyone knows what might have happened and what I should do. As mentioned before, the previous owner put in "a GM Hot cam, upgraded springs, new lifters, new valve seals." Something had to cause this to happen. What further damage could there be, could the piston be damaged?
I found all of the parts I need to fix this damaged rocker arm. These are the original roller rocker arms on the car, found one on eBay. Ordered new from GM valve keepers (keys - had to buy 10), a new spring keeper, and a valve cover bolt stud (to head). It looks to me like the keys came loose somehow on the valve spring. Is it possible the "upgraded" springs are too stiff or strong for the stock keys?
Any help very appreciated.

0Paul Ruggeri

Those rockers are suppose to be selfaligning. Looks like one wasn't. Check the pushrod to see if its bent. I would recommend hardened push rods and guide plates. That's what I run with my Hotcam. That should eliminate the problem.

aklim

Before I spend any more money, I would take the head off to make sure that the piston didn't get a kiss.

mcox8051

The pushrod is perfectly straight. Can I do a compression check to see if the piston has a crack or hole? What could cause the rocker arm to jump off the valve? I see what you mean by guide plates keeping the pushrod from moving thus helping to hold the rocker arm.

aklim

Nope. I lost a chunk of piston thanks to the TFS head screwing up and the compression is fine. Nothing like a visual to see.

mtwoolford

had almost the exact same thing happen to my 96 LT4; just not as bad. the valve rocker arm did not rotate off the valve stem, but the valve stem did chew up the rocker arm next to the roller. Had a stock cam in it at the time. Further investigation revealed a cam with three bad lobes .... good luck.

p.s. for what it's worth, in my opinion, on a "self aligning" rocker, the "ears" that hold it in alignment could have / should have been made taller.

mcox8051

I can't imagine the cam being worn, it has less than 1500 miles on it. And the guides on the roller are not worn. Its almost like it may have floated or whatever, enough to let the keys come loose. I don't know what to do.

hooked073

A couple of things could have happened. installer could have adjusted valves to tight wiped the cam. may not have had the valve adjusted tight enough, did not have rocker alined, all kinds of things. What I would do is pull up on the valve stem and rotate it with your fingers it should rotate smoothly. If it does I would throw a new rocker on and see what happens. Fact is if you did any internal damage you are going to have to tear it down any way. why jump to the worse case sanaro? PS replace the push rod too. From picture it is hard to tell but my guess installer had the rocker misaalined and it was not on the roller it was on the rocker itself if you look at it close it looks like the valve stem has been riding in that spot long enough to make a smooth indentation before it busted. My quess is youll be fine. The only thing that worries me is the keepers were of the valve and that would let the valve drop. But if it rotates like I said I would give it a try

Muffin

I can see the rocker backing off causing the damage but can someone explain how the split keepers came off the valve and out of the retainer. I agree with aklim, I would make some attempt to determine if there was any piston damage, borescope maybe.

STL94LT1

FYI: The stock LT4 rockers are non-adjustable, you just torque them down and go.

If the valve dropped, there is a pretty good chance you have damage. Either get a borescope or pull the head.

mcox8051

I will try the borescope first to look at the piston. Do auto parts stores rent them? The valve does turn smoothly and goes up and down freely. I'm hoping it just rode up and down on the piston and the rocker took the damage. I think the car has stock pushrods so just get a new one from GM? I don't want this to happen again. Should I install guide plates? Would this help keep things in place, as far as the rockers getting off the valves? If so, what brand is best? I have read a lot about whether you can install them under the rocker stud and not have to machine the heads, looks like there is clearance since the rocker rides on the push rods and valves. THANKS GUYS!

STL94LT1

You can't use guide plates with your self-aligning rockers.

hooked073

Muffin I was thinking about that after I wrote my post. quick guess is the installer only had one retainer installed right. after a couple thousand miles a bad install caused the other retainer to dislodge and caused all of this. or a combination of things. but you are right it is very rare for retainers to come off. Infact almost impossible if things are together right.

Churchkey

If the rocker rides the retainer the keepers can pop out.

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To the OP:

If it were my problem the cylinder head would come off & the damaged valve would be replaced. Once a valve has made contact with a piston its integrity has been compromised. The next 6K rpm could result in valve failure. IE: The valve head separating from the stem. It can & will be ugly. Broken piston, piston debris in other cylinders, cracked block, broken head, bent rod(s) & so on.

Suggest having someone with engine knowledge check your car. In your first post you told of some "clashing noise on start up". This issue also needs to be addressed or perhaps you have found it.

Good luck with your project.

Hooked on Vettes

Looking at the this picture it appears there is something still threaded onto the rocker arm stud.

Does the rocker arm nut have a threaded bushing pressed into it that has seperated from the rocker arm nut?

engle1147

Bet the polly lock wasn't tightend correctly after lash/preload was set by PO....the polly lock might have continued to back off over time causing stud thread damage along the way then finally the rocker arm jumped off the stem and depressed the upper spring seat allowing the retainers to escape.

aklim

Post 1 pic 3 shows that the valve contacted some part besides what it should. Look at the intended contact area vs the other parts. The contact area is lower. This means that there was more lift than it should have had. No way I would go further without seeing if the piston and valve kissed. I would also replace the spring and check the valve itself out. The more I think about it, the more I think the head should come off. The valve could have had abnormal wear and be shorter than the rest, it might have kissed the piston, the valve might be bent, etc, etc.

mcox8051

Sounds like I will have to pull the head. I have a couple of friends who race and do their own engine work, I will consult them. There are not any speedshops around and not many shops at all familiar with these engines that I would trust. The threads are not damaged or anything, just look funny in picture, the rocker nut was tight. The pushrod end of the rocker was still on the pushrod. My concern is: What caused this to happen? Could the lifter have collapsed and caused it? Since the cam and springs were upgraded should I install guide plates? I read somewhere that is a must. I think if it were installed wrong it would have failed sooner. I drove the car a 1000 miles home, 13 hours straight. Was just cruising around when this happened. I started hearing a ticking noise first, then it kept getting worse. The oil is only a quart low. Something had to happen to relieve the pressure between the pushrod, rocker, and valve, enough to let the rocker slip off. Is it possible the keepers popped out and the spring pushed the rocker off? I tried them back on the valve and everything seems to fit right.

STL94LT1

OK once again, you cannot install guide plates with your self-aligning rockers. To run guide plates you will need to buy non self-aligning rockers, rocker studs, guide plates, and hardened pushrods.

Pete K

Any of the above.
The only way to know is with a full visual assessment on your end.
Keepers are cheap. Replace them all. Replace all rocker studs with arp's and add guideplates before installling new non self aligning rockers.
Lifters did nt likely contribute to your problem, but it is possible. I would change them out, as they are cheap enough.
As far as the valve is concerned, if it passes a visual inspection, have a local shop chuck it up, and kiss it with the stones. If it is bent, it will show up.

If I was a betting man, I would throw a few buck on the likelyhood the installer did an incorrect valvetrain adjustment. If he did not know the valvetrain was different than a typical sbc, he may not have adjusted it as a positive stop set up.