Rocker Arm falling off valve problem ...
Thread Starter
Advanced
Joined: Sep 2010
Posts: 86
Likes: 4
From: Hampstead NC
Rocker Arm falling off valve problem ...
In the general section, you will find reference to my son's saving a 94 LT1 ZF6 with 120k miles Corvette thread. Since saving her, she has made us work to get her running well. Plugs were shot, fuel pump had gone west. Starter was reluctant .. all have been overcome!
After getting her sorta running, one of the first problems we came across was a displaced rocker arm.
. The car had not started for 18-24 months, and so we sort of accepted that things would need to run in again. After checking the push rod, and resetting the lash, the car ran fine.
Well, until my son got enthusiastic, and after 50 miles of steady cruising, tried a few 6th-3rd interstate blasts (to get the last of the cobwebs out?), and once again, a rocker arm fell off the valve ...
I've run and restored old Triumph sportscars and worked on a lot of LBC's (all of which have solid lifters) and so I'm not very familiar with the hydraulic versions ... do we have a problem with the lifters, or maybe the cam?
Any help or advice welcomed!
After getting her sorta running, one of the first problems we came across was a displaced rocker arm.
. The car had not started for 18-24 months, and so we sort of accepted that things would need to run in again. After checking the push rod, and resetting the lash, the car ran fine. Well, until my son got enthusiastic, and after 50 miles of steady cruising, tried a few 6th-3rd interstate blasts (to get the last of the cobwebs out?), and once again, a rocker arm fell off the valve ...
I've run and restored old Triumph sportscars and worked on a lot of LBC's (all of which have solid lifters) and so I'm not very familiar with the hydraulic versions ... do we have a problem with the lifters, or maybe the cam?
Any help or advice welcomed!
Thread Starter
Advanced
Joined: Sep 2010
Posts: 86
Likes: 4
From: Hampstead NC
Someone did suggest that we might be suffering from collapsed lifters, which he said can go bad once in a while ... doesn't sound like a likely answer, but since I know nothing about the darned things, who knows?
Last edited by atgordon; Sep 30, 2010 at 10:07 PM.
Melting Slicks
Joined: Jun 2010
Posts: 2,178
Likes: 1
Can you push it down with your fingers, the spring that is. Sometimes they are hard to see, as they have dampers inside.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
1) check the spring
2) Could be a collapsed lifter....but you should hear a lot of ticking because the lifter is not pumping up to take out the slack between the rod and the rocker arm.
3) check the threads on the rocker arm stud.
4) check the rock arm stud...is it pulling out?
2) Could be a collapsed lifter....but you should hear a lot of ticking because the lifter is not pumping up to take out the slack between the rod and the rocker arm.
3) check the threads on the rocker arm stud.
4) check the rock arm stud...is it pulling out?
Drifting
Joined: Aug 2006
Posts: 1,624
Likes: 2
From: Canandaigua New York
Another thing you could do is remove the spring and measure it's height compared to a new stock spring.
I don't have the specs off hand but if the spring is good, the height should be nearly identical.
You could also have them tested for 'compression,' which is basically a spring compressor with a gauge which measures the amount of force necessary to fully compress the spring.
Hydraulic lifters are adjusted by loosening them up until they 'click' and then tightening them up until the click goes away.
Then you give them another 3/4 to a full turn and you're done.
If everything checks out, then you may need to install push rod 'guides' to keep them aligned.
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Le Mans Master
Joined: Mar 2000
Posts: 8,950
Likes: 4
From: Lafayette LA
Pull the rocker arm off, and flip it over. Make sure the little ears that sit on either side of the valve tip aren't damaged. Those ears are what makes them self-aligning rockers and eliminate the need for guide plates.
While you have it off, swap it with one of the other rocker arms. If it keep popping off when swapped to another valve, you know the arm is bad. If the new arm keeps popping off that valve, you know it's not the arm.
Better yet, if your springs are all good, swap to a set of non-self aligning roller rockers with a set of guide plates.
While you have it off, swap it with one of the other rocker arms. If it keep popping off when swapped to another valve, you know the arm is bad. If the new arm keeps popping off that valve, you know it's not the arm.
Better yet, if your springs are all good, swap to a set of non-self aligning roller rockers with a set of guide plates.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
BTW, you shouldn't run guide plates with self-aligning rocker arms at the same time. It's one of those "No-no's".
Unless someone changed them, your springs should be singles, your studs are screw-in types.
Check the pushrod for being bent if you haven't already. Just roll it across something flat; mirror, kitchen table, washer lid, etc. Look for any sign of wiggle.
Yes, you could have a collasping lifter and one or both of the self-aligning tabs could be broken or worn away.
Stock rocker nuts are slightly oblong ID which is what gives them the ability to stay in place when tightened. When loosened and retightened several times they oblong rounds out and the nut can't hold fixed well any longer. New nuts are inexpensive and available at most auto parts stores. If one of your is bad, I'd change all of them.
You're going to have to get down really close to that rocker area and look for anything different from the others - bent, broken, shiny areas, retainer, underside of rocker arm, broken spring, etc. Hopefully the cause is up top, otherwise you'll be looking at pulling the intake manifold.
Keep us posted.
Jake
Jake
Unless someone changed them, your springs should be singles, your studs are screw-in types.
Check the pushrod for being bent if you haven't already. Just roll it across something flat; mirror, kitchen table, washer lid, etc. Look for any sign of wiggle.
Yes, you could have a collasping lifter and one or both of the self-aligning tabs could be broken or worn away.
Stock rocker nuts are slightly oblong ID which is what gives them the ability to stay in place when tightened. When loosened and retightened several times they oblong rounds out and the nut can't hold fixed well any longer. New nuts are inexpensive and available at most auto parts stores. If one of your is bad, I'd change all of them.
You're going to have to get down really close to that rocker area and look for anything different from the others - bent, broken, shiny areas, retainer, underside of rocker arm, broken spring, etc. Hopefully the cause is up top, otherwise you'll be looking at pulling the intake manifold.
Keep us posted.
Jake
Jake
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
If the rocker falls off, It could indicate a seriously defective spring. I would also suspect a bent valve.
In it's past life, it may have had an injector leaking and gotten a hydraulic lock and bent the pushrod or the valve.
If the rocker is falling off the valve, the valve speed is reduced,
The cam and lifter are going back to the base circle diameter, and the valve isn't closed yet, indicating a bent valve or weak spring.
THe engine may operate ok when cold or at low speeds, but rev it up, and the slow valve is rearing it's ugly head.
In it's past life, it may have had an injector leaking and gotten a hydraulic lock and bent the pushrod or the valve.
If the rocker is falling off the valve, the valve speed is reduced,
The cam and lifter are going back to the base circle diameter, and the valve isn't closed yet, indicating a bent valve or weak spring.
THe engine may operate ok when cold or at low speeds, but rev it up, and the slow valve is rearing it's ugly head.
Last edited by coupeguy2001; Oct 3, 2010 at 11:01 AM.
