LT4 Roller Rockers
Thread Starter
Cruising
Joined: Apr 2002
Posts: 11
Likes: 1
From: NJ
LT4 Roller Rockers
All,
I am somewhat new to messing with valvetrains and am looking to get a few basic newbie questions answered relating to the rocker arms on my LT4. I have searched on this forum and several others trying to find the answers to now avail, so I am hoping somebody can answer the question on this thread.
Recently, I have been noticing a tapping noise coming from the driver's side of my LT4. It seemed to be tapping at 1/2 engine speed. After doing some research on the forums and some investigating, I felt that it is likely coming from the valvetrain. I pulled the valve covers off my engine today and everything looked very nice and clean. After doing some poking around I found that a couple of the roller rockers felt a bit loose. I could rotate them slightly left and right. My manual (and the forums) indicate that the roller rockers in the LT4 are simply torque to spec (18 ft. lbs. according to my manual). I proceeded to loosen up the bolts holding the rockers down and then retorque them to the 18 ft. lbs. This process tightened some of the loose rockers, but others continue to have a little bit of play in them. I closed everything up and started the car. The noise was significantly reduced, but still present. Based on the noise reduction, I believe that the issue is still in the valvetrain. My questions are:
1. Is the 18 ft. lbs. of torque the correct specification for these roller rockers?
2. Some of the rockers can be turned on the studs left and right while at the 18 lb. ft. torque, is there any issue with increasing the torque on the bolts to anchor the rockers more firmly? It appears that this would simply anchor the mounting point on the rocker to the stud with no significant impact to the valvtrain, but I wanted to be sure.
3. Some of the rockers have a slight amount of play such that you can rotate the rocker left and right while holding the axis of normal rotation stationary. I guess what I am trying to say is that the bearings of some of the rockers are a tiny bit loose. Is this normal or do they need to be replaced?
The rockers are the stock rockers with ~50K miles on them. The tapping sounds almost like a sewing machine at idle. Any help is greatly appreciated.
I am somewhat new to messing with valvetrains and am looking to get a few basic newbie questions answered relating to the rocker arms on my LT4. I have searched on this forum and several others trying to find the answers to now avail, so I am hoping somebody can answer the question on this thread.
Recently, I have been noticing a tapping noise coming from the driver's side of my LT4. It seemed to be tapping at 1/2 engine speed. After doing some research on the forums and some investigating, I felt that it is likely coming from the valvetrain. I pulled the valve covers off my engine today and everything looked very nice and clean. After doing some poking around I found that a couple of the roller rockers felt a bit loose. I could rotate them slightly left and right. My manual (and the forums) indicate that the roller rockers in the LT4 are simply torque to spec (18 ft. lbs. according to my manual). I proceeded to loosen up the bolts holding the rockers down and then retorque them to the 18 ft. lbs. This process tightened some of the loose rockers, but others continue to have a little bit of play in them. I closed everything up and started the car. The noise was significantly reduced, but still present. Based on the noise reduction, I believe that the issue is still in the valvetrain. My questions are:
1. Is the 18 ft. lbs. of torque the correct specification for these roller rockers?
2. Some of the rockers can be turned on the studs left and right while at the 18 lb. ft. torque, is there any issue with increasing the torque on the bolts to anchor the rockers more firmly? It appears that this would simply anchor the mounting point on the rocker to the stud with no significant impact to the valvtrain, but I wanted to be sure.
3. Some of the rockers have a slight amount of play such that you can rotate the rocker left and right while holding the axis of normal rotation stationary. I guess what I am trying to say is that the bearings of some of the rockers are a tiny bit loose. Is this normal or do they need to be replaced?
The rockers are the stock rockers with ~50K miles on them. The tapping sounds almost like a sewing machine at idle. Any help is greatly appreciated.
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
Likes: 71
From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Are you checking these all from one engine position? At any one position, some will be tight and some will be loose depending on where any particular cylinder is in it's cycle.
Thread Starter
Cruising
Joined: Apr 2002
Posts: 11
Likes: 1
From: NJ
Corvette Kid NC,
Thanks for the reply. Yes, I am checking all of the rockers with the engine in a single position. I did not want to rotate the crank manually for fear of upsetting the crank position calibration in the computer. My LS-1 needs to go through a relearn procedure for the crank position if the original relationship is disturbed with the computer off. I have the needed hardware and software to run the relearn process for that vehicle but I do not have the correct hardware to do it for a LT-4. I assume that this is also needed on the LT-4. If the process does not need to be done on the LT-4 or there is a simple way of doing this without software please let me know.
As for your comment, I was figuring that some rockers would be looser than others due to their individual positions in the engine cycle. However, these roller rockers are torque to spec, and the torque on the bolt does not seem to impact the rocker arm travel at all. It only anchors the rocker to the stud more firmly. There is no impact on the force required to push the rocker or the arc travel, so I am thinking that torquing them so that thet are anchored to the head should make them quiet, without impacting the valvetrain. However, I want to make sure that my interpretation of the configuration of the rockers and the impact to the valvetrain is correct before tightening them to the head. It may also be that they just need to be replaced because the specified torque for the bolt is not holding them to the head properly.
Thanks for the reply. Yes, I am checking all of the rockers with the engine in a single position. I did not want to rotate the crank manually for fear of upsetting the crank position calibration in the computer. My LS-1 needs to go through a relearn procedure for the crank position if the original relationship is disturbed with the computer off. I have the needed hardware and software to run the relearn process for that vehicle but I do not have the correct hardware to do it for a LT-4. I assume that this is also needed on the LT-4. If the process does not need to be done on the LT-4 or there is a simple way of doing this without software please let me know.
As for your comment, I was figuring that some rockers would be looser than others due to their individual positions in the engine cycle. However, these roller rockers are torque to spec, and the torque on the bolt does not seem to impact the rocker arm travel at all. It only anchors the rocker to the stud more firmly. There is no impact on the force required to push the rocker or the arc travel, so I am thinking that torquing them so that thet are anchored to the head should make them quiet, without impacting the valvetrain. However, I want to make sure that my interpretation of the configuration of the rockers and the impact to the valvetrain is correct before tightening them to the head. It may also be that they just need to be replaced because the specified torque for the bolt is not holding them to the head properly.
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
Likes: 71
From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
I have a '96 manual and so checked the procedure for tightening them. It doesn't mention that a rocker has to be in a relaxed position when torquing but it sure seems like it should be. Anyhow, if you've still got some noise, I think I'd recommend removing them all for a full inspection as well as looking at everything else in the system for unusual wear, etc.
