Putting rockers back on correctly
Thread Starter
Melting Slicks
Joined: Nov 2011
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From: Virginia
Putting rockers back on correctly
I have read numerous times that when you torque a rocker back to 22ft lbs the lifter needs to be on the base circle of the cam. So by not doing this can it cause excessive valvetrain noise and if so, why? I assume you do not get an accurate lifter preload? I am trying to learn a little bit about valvetrain geometry. I’m wondering because I know mine were not done this way and I’m wondering if that’s why I have such a loud *** sewing machine motor. I’ll be swapping out my 7.4 pushrods soon and want to make sure it’s done correctly bc this car is aggravating the crap out of me.
Team Owner
Joined: Mar 1999
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From: At the beach in little Rhody
Given that, the fact that they were tightened differently will not affect the noise as the rockers should be down against the head. Not sure what your noise is, but lifter preload can be an issue and that is solved by measuring for the correct pushrod. The stock setup is not adjustable so the lifter preload is determined solely by pushrod length. Noise can also be generated due to the lobe profile of the cam, for example the Comp XER profile is more aggressive and generally noisier than less aggressive profiles.
Last edited by vettenuts; Jun 17, 2019 at 09:51 AM.
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Team Owner
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From: Western NY
And that's why I was very careful to spin the engine around, and tightening the bolts the first time I had the rockers off and on. However, I just bolted them down, the second time around, because the HB bolt is difficult to access, on an ATI balancer.
Thread Starter
Melting Slicks
Joined: Nov 2011
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From: Virginia
This and you won't get the proper bolt preload by tightening when off the base circle.
Given that, the fact that they were tightened differently will not affect the noise as the rockers should be down against the head. Not sure what your noise is, but lifter preload can be an issue and that is solved by measuring for the correct pushrod. The stock setup is not adjustable so the lifter preload is determined solely by pushrod length. Noise can also be generated due to the lobe profile of the cam, for example the Comp XER profile is more aggressive and generally noisier than less aggressive profiles.
Given that, the fact that they were tightened differently will not affect the noise as the rockers should be down against the head. Not sure what your noise is, but lifter preload can be an issue and that is solved by measuring for the correct pushrod. The stock setup is not adjustable so the lifter preload is determined solely by pushrod length. Noise can also be generated due to the lobe profile of the cam, for example the Comp XER profile is more aggressive and generally noisier than less aggressive profiles.
Team Owner
Joined: Mar 1999
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From: At the beach in little Rhody
Shouldn't be a valve issue. What measurements did you get on the passenger side?
Were measurements taken prior to using the current pushrods?
Most vendors just push 7.400" because it will adjust for the difference in base circle from stock as they are slightly longer. You may also need to adjust your preload as some have found deeper preloads result in more noise.
Were measurements taken prior to using the current pushrods?
Most vendors just push 7.400" because it will adjust for the difference in base circle from stock as they are slightly longer. You may also need to adjust your preload as some have found deeper preloads result in more noise.
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Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,187
Likes: 265
From: Virginia
Shouldn't be a valve issue. What measurements did you get on the passenger side?
Were measurements taken prior to using the current pushrods?
Most vendors just push 7.400" because it will adjust for the difference in base circle from stock as they are slightly longer. You may also need to adjust your preload as some have found deeper preloads result in more noise.
Were measurements taken prior to using the current pushrods?
Most vendors just push 7.400" because it will adjust for the difference in base circle from stock as they are slightly longer. You may also need to adjust your preload as some have found deeper preloads result in more noise.
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I just go down the line, take it slow especially if you are going against heavy spring pressure but you can feel the bolt stop and when you get to that point you can then torque the bolt... personally I would never use a cordless impact to run these bolts down, I prefer to use hand tools in this situation
Team Owner
Joined: Mar 1999
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From: At the beach in little Rhody
On the passenger side I measured a preload of close to .090. Measurements were not taken prior. As far as the 7.400 I provided those to the shop because that’s what Texas Speed recommended. The installer said the ls7 lifters have a wide acceptable preload range so the 7.4 would be fine. I’m on the higher end of the preload range (I believe) so that’s why I’m surprised by the noise. I called Texas Speed back and they suggested if I were going to try and different preload then to drop down to a 7.375. Maybe 7.425 would be too much?
Thread Starter
Melting Slicks
Joined: Nov 2011
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From: Virginia
Your measured preload of 0.090" is about what I have measured on a bone stock motor. I would look around at what the LS7 lifters like for preload. I don't have them so can't comment, but I believe others have found a little less preload helps with noise. Just be sure you don't have a mechanical issue (bad lobe, etc.). If changing pushrods, I would also go to a larger diameter to prevent valve bounce. Valve bounce will take out a lobe and lifter wheel.
Team Owner
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From: At the beach in little Rhody
You can get custom length if you want, check Manton 11/32" pushrods. They manufacture per order and based upon your measurements. Comp also makes Pro LS pushrods in 11/32" OD and they are available in 0.025" length increments. There are options if you want to make a change, and yet you will benefit from larger OD pushrods.
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