Chevy 350 loose rocker - KCSR

mack246 · 2012-06-24, 04:04 AM

Ive been working a project car for a friend of mine, its a 1978 Camaro with a cast iron block and a set of 327 "Camel Hump" heads. Long story short, was able to get the Camaro started and idle for a bit. While the car was idle, I could hear a ratteling sound coming from the passenger side valve cover. Took cover off and noticed the #2 cylinder intake rocker was loose, and I mean loose. Loose enougth that you could grab it and turn side to side freely. So then the took drive side valve cover off, and went through the firing order and re-tighten all the rockers. Put the car back to togeter and re-started it. With in a couple of mintues, the same sound was back, still on passenger side. Took valve cover back off and again #2 cylinder intake rocker was loose, like I never retighten it.

All of the other rockers in the passenger head were still tight. I took the actual rocker off and it shows no signs of any adnormal wear. The studs has been pinned, and there were no groves or pitts on the smooth portion of the studs. Pulled the push rob out, and check it. Oil passage is not plugged, you can see through it. Rolled the push rod on the work bench, and its not bent. There was oil getting to the rocker assembly.

I am just out of ideas on how to keep the rocker tight and not coming loose again. Any help with this will be amazing. Thanks in advance for any help.

bryanwheat · 2012-06-24, 05:31 AM

First off, are you sure that there is no damage to the lobe on the cam. Does the rocker seem to move as much as the others. Second, how are you tightening them. The correct process (assuming that you have a hydralic cam) is to turn the engine until the valve is closed all the way, than tighten the nut until there is zero play between the push rod and rocker. After you reach this point add an extra 1/2 to 3/4 turns on the nut. It the nut still hard to turn don the stud? They should be pretty stiff. It is possible that the stud is starting to pull from the head. Those heads have press in studs and can be pulled out if aftermarket cams are used.

mack246 · 2012-06-24, 06:26 AM

In regards to the first question, I do know know. The heads were removed due to someone drilling a hole into one of the heads for a "ghetto rigged" alternator bracket. When they did this, they drilled into a water jacket. The head was replace. The machine shop also did a valve job as well. So the crank and cam, as well as the timing were never removed.

In regards to question number two, that is how we tighten the rockers. We put the cylinder # 1 on the compression stroke which causes both valves to be closed. We then turned the crank by hand, and followed the firing order to complete both heads. When the "play" with the push rod was gone, we put an extra 1/2 turn on them to set the pre-load.

When the machine shop did the head work, they pinned all studs.

I just cannot see how after tighting the rockers twice, the same rocker would become loose.

bwiencek · 2012-06-24, 11:05 AM

Since the studs are pinned and not pulling out - You've got one of two things happening - either the lock-nut on the rocker is just plain wore out - they're supposed to be slightly crimped to provide friction when tightening the rocker down and not back off - if they've been run up and down a lot this crimped area can get loose and the nut can walk back off - this will be obvious since the adjustment will have backed off - I'm going to guess that this is the most likely thing since the camshaft was already broken in and wasn't changed.

The next is a camshaft going flat - pull the lifter out and inspect the bottom - if you can't get to it (it takes a lifter pull tool that grabs it and can pull it up to inspect it - goes through the pushrod hole then you can fish it out through the distributor hole or just turn it a bit and look through another pushrod hole) - check the lift in relation to the others, pull and cut apart the oil filter and check for shavings, and check the height of the nut compared to others - if it's down further then I'd just pull the intake and take a look - the gaskets are cheap enough and I suspect you'll be putting a cam in it if that's what you find...

Mad Dog · 2012-06-24, 04:07 PM

Other things to look at:
Bent pushrod
Lifter collapsed
The above suggestions are much more likely, and I'm betting on a flat cam. Remember to run high zinc oil or additives in flat tappet engines.

RiskyRick · 2012-06-24, 05:24 PM

Also check the length of the pushrod vs the rest of them. Had a similar issue on my dad's car, turned out the pushrod wasn't bending, but instead collapsing straight down on one end.

mack246 · 2012-06-26, 08:47 AM

And the answer to my question was......................it was the nut as well as the stud. The nut some how stripped itself out, and did not have the three dimples on top of it to act as a lock washer. By the nut backing off, it had caused the thread of the stud to get burgered up. The stud was re-tapped and the new nut was installed. This fixed the problem. After fixing it, car was ran for about 5 mins with no sound. Valve cover was removed and rocker was still tigh

I just want to say thanks for all those whos replied, thanks again.

2012-06-24, 04:04 AM	#1
mack246 Join Date: Dec 2007 Location: Topeka, KS 66614 Posts: 277 Post Thanks / Like Thanks (Given): 0 Thanks (Received): 0 Likes (Given): 0 Likes (Received): 0 Dislikes (Given): 0 Dislikes (Received): 0	Chevy 350 loose rocker Ive been working a project car for a friend of mine, its a 1978 Camaro with a cast iron block and a set of 327 "Camel Hump" heads. Long story short, was able to get the Camaro started and idle for a bit. While the car was idle, I could hear a ratteling sound coming from the passenger side valve cover. Took cover off and noticed the #2 cylinder intake rocker was loose, and I mean loose. Loose enougth that you could grab it and turn side to side freely. So then the took drive side valve cover off, and went through the firing order and re-tighten all the rockers. Put the car back to togeter and re-started it. With in a couple of mintues, the same sound was back, still on passenger side. Took valve cover back off and again #2 cylinder intake rocker was loose, like I never retighten it. All of the other rockers in the passenger head were still tight. I took the actual rocker off and it shows no signs of any adnormal wear. The studs has been pinned, and there were no groves or pitts on the smooth portion of the studs. Pulled the push rob out, and check it. Oil passage is not plugged, you can see through it. Rolled the push rod on the work bench, and its not bent. There was oil getting to the rocker assembly. I am just out of ideas on how to keep the rocker tight and not coming loose again. Any help with this will be amazing. Thanks in advance for any help. __________________ Last edited by mack246; 2012-06-24 at 06:28 AM..

2012-06-24, 06:26 AM	#3
mack246 Join Date: Dec 2007 Location: Topeka, KS 66614 Posts: 277 Post Thanks / Like Thanks (Given): 0 Thanks (Received): 0 Likes (Given): 0 Likes (Received): 0 Dislikes (Given): 0 Dislikes (Received): 0	In regards to the first question, I do know know. The heads were removed due to someone drilling a hole into one of the heads for a "ghetto rigged" alternator bracket. When they did this, they drilled into a water jacket. The head was replace. The machine shop also did a valve job as well. So the crank and cam, as well as the timing were never removed. In regards to question number two, that is how we tighten the rockers. We put the cylinder # 1 on the compression stroke which causes both valves to be closed. We then turned the crank by hand, and followed the firing order to complete both heads. When the "play" with the push rod was gone, we put an extra 1/2 turn on them to set the pre-load. When the machine shop did the head work, they pinned all studs. I just cannot see how after tighting the rockers twice, the same rocker would become loose. __________________

2012-06-24, 11:05 AM	#4
bwiencek Join Date: Feb 2004 Location: Greenwood, MO Posts: 2,147 Post Thanks / Like Thanks (Given): 0 Thanks (Received): 6 Likes (Given): 0 Likes (Received): 7 Dislikes (Given): 0 Dislikes (Received): 1	Since the studs are pinned and not pulling out - You've got one of two things happening - either the lock-nut on the rocker is just plain wore out - they're supposed to be slightly crimped to provide friction when tightening the rocker down and not back off - if they've been run up and down a lot this crimped area can get loose and the nut can walk back off - this will be obvious since the adjustment will have backed off - I'm going to guess that this is the most likely thing since the camshaft was already broken in and wasn't changed. The next is a camshaft going flat - pull the lifter out and inspect the bottom - if you can't get to it (it takes a lifter pull tool that grabs it and can pull it up to inspect it - goes through the pushrod hole then you can fish it out through the distributor hole or just turn it a bit and look through another pushrod hole) - check the lift in relation to the others, pull and cut apart the oil filter and check for shavings, and check the height of the nut compared to others - if it's down further then I'd just pull the intake and take a look - the gaskets are cheap enough and I suspect you'll be putting a cam in it if that's what you find... __________________ Too many cars too little time...

2012-06-24, 04:07 PM	#5
Mad Dog Join Date: Apr 2004 Location: Back from the dead Posts: 4,414 Post Thanks / Like Thanks (Given): 11 Thanks (Received): 16 Likes (Given): 7 Likes (Received): 82 Dislikes (Given): 2 Dislikes (Received): 1	Other things to look at: Bent pushrod Lifter collapsed The above suggestions are much more likely, and I'm betting on a flat cam. Remember to run high zinc oil or additives in flat tappet engines. __________________

2012-06-26, 08:47 AM	#7
mack246 Join Date: Dec 2007 Location: Topeka, KS 66614 Posts: 277 Post Thanks / Like Thanks (Given): 0 Thanks (Received): 0 Likes (Given): 0 Likes (Received): 0 Dislikes (Given): 0 Dislikes (Received): 0	And the answer to my question was......................it was the nut as well as the stud. The nut some how stripped itself out, and did not have the three dimples on top of it to act as a lock washer. By the nut backing off, it had caused the thread of the stud to get burgered up. The stud was re-tapped and the new nut was installed. This fixed the problem. After fixing it, car was ran for about 5 mins with no sound. Valve cover was removed and rocker was still tigh I just want to say thanks for all those whos replied, thanks again. __________________

2012-06-24, 05:31 AM	#2
bryanwheat Join Date: Jan 2007 Location: Columbia Posts: 3,931 Post Thanks / Like Thanks (Given): 1 Thanks (Received): 22 Likes (Given): 7 Likes (Received): 61 Dislikes (Given): 4 Dislikes (Received): 4	First off, are you sure that there is no damage to the lobe on the cam. Does the rocker seem to move as much as the others. Second, how are you tightening them. The correct process (assuming that you have a hydralic cam) is to turn the engine until the valve is closed all the way, than tighten the nut until there is zero play between the push rod and rocker. After you reach this point add an extra 1/2 to 3/4 turns on the nut. It the nut still hard to turn don the stud? They should be pretty stiff. It is possible that the stud is starting to pull from the head. Those heads have press in studs and can be pulled out if aftermarket cams are used.