Shimming the rockers w/ AFR's cut .030....gotta do something
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I ordered AFR's milled .030
My gasket is going from stock (.054) thickness to .045
My cam is an MTI C1 Lunati grind which obviously has a smaller base circle HENCE the hardened 7.4 pushrods went in when I put the cam in. So now that my head is effectivley .040 lower than before here is my question.......
I already have the 7.4 hardened push rods so can I just shim the rockers and I'm good to go right ?
Is there any negative effect or anything I better to know when doing this?
Nothing popped up on my search, MTI sells shims. It looks like lots of people are going to be running milled AFR's so might as well get this answered. Yes I know you have to measure and ideally use a pushrod checker and whatever but the bottom line is math says the head is .040 lower so I'm just going by the math here.
My gasket is going from stock (.054) thickness to .045
My cam is an MTI C1 Lunati grind which obviously has a smaller base circle HENCE the hardened 7.4 pushrods went in when I put the cam in. So now that my head is effectivley .040 lower than before here is my question.......
I already have the 7.4 hardened push rods so can I just shim the rockers and I'm good to go right ?
Is there any negative effect or anything I better to know when doing this?
Nothing popped up on my search, MTI sells shims. It looks like lots of people are going to be running milled AFR's so might as well get this answered. Yes I know you have to measure and ideally use a pushrod checker and whatever but the bottom line is math says the head is .040 lower so I'm just going by the math here.
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Guys...
The amount of "shim" you use under the rocker stands will have a direct effect on the valvetrain geometry and the "wipe" pattern created from the rocker rolling across the valve stem tip as the cam lifts the rocker and sets it down. Ideally, you want this small rectangular patch or "wipe pattern" to be located dead center over the valvestem tip. More shim will move it towards the Exh. side, less shim will move it closer to the intake side. Once you have achieved the correct geometry, the length of the pushrod is determined by simply measuring (with an adjustable pushrod ideally) what you need to provide the correct or desired amount of lifter preload. Pushrod length does NOT effect the actual valve train geometry (in a "shaft mount" style set-up) which is actually more important then the pre-load on your lifters. The correct "geometry" should dictate pushrod length, not the other way around.
BOTH of these issues need to be addressed if your looking for longevity and additional power from correct valvetrain geometry etc...
Hope this sheds more light on the situation.
Tony M.
The amount of "shim" you use under the rocker stands will have a direct effect on the valvetrain geometry and the "wipe" pattern created from the rocker rolling across the valve stem tip as the cam lifts the rocker and sets it down. Ideally, you want this small rectangular patch or "wipe pattern" to be located dead center over the valvestem tip. More shim will move it towards the Exh. side, less shim will move it closer to the intake side. Once you have achieved the correct geometry, the length of the pushrod is determined by simply measuring (with an adjustable pushrod ideally) what you need to provide the correct or desired amount of lifter preload. Pushrod length does NOT effect the actual valve train geometry (in a "shaft mount" style set-up) which is actually more important then the pre-load on your lifters. The correct "geometry" should dictate pushrod length, not the other way around.
BOTH of these issues need to be addressed if your looking for longevity and additional power from correct valvetrain geometry etc...
Hope this sheds more light on the situation.
Tony M.
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Originally Posted by Beast96Z
I have AFR's milled .024 with .045 gaskets. When I set my rockers up I needed a .075 thick shim to get the pre-load right. I used the 7.400 PR's and had no problem.
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Originally Posted by Beast96Z
I have AFR's milled .024 with .045 gaskets. When I set my rockers up I needed a .075 thick shim to get the pre-load right. I used the 7.400 PR's and had no problem.
Maybe I'm missing something, but I don't understand the point of the original question exactly. If you have the correct length pushrods for the application and are using stock lifters/stock replacement lifters and stock replacement non adjustable rockers I don't understand the need to shim the rockers? The only times I've heard shimming being done is when trying to get lifter preload exactly right with "touchy" lifters like the R's.
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Thanks guys, Thanks Tony. I am going to re-read the thread a few times.
I was just planning on tightening the rockers to 22 ft/lb after 0 lash. I was under the impression that there is nothing to adjust (pre-load) with the stock rockers & lifters. The length of the pushrod with the milled heads was my only concern (geometry)and that was evidently misplaced. I did some reading on verifying the wear pattern and using the shims in that respect.
I was just planning on tightening the rockers to 22 ft/lb after 0 lash. I was under the impression that there is nothing to adjust (pre-load) with the stock rockers & lifters. The length of the pushrod with the milled heads was my only concern (geometry)and that was evidently misplaced. I did some reading on verifying the wear pattern and using the shims in that respect.
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Originally Posted by Mirek
I ordered AFR's milled .030
My gasket is going from stock (.054) thickness to .045
My cam is an MTI C1 Lunati grind which obviously has a smaller base circle HENCE the hardened 7.4 pushrods went in when I put the cam in. So now that my head is effectivley .040 lower than before here is my question.......
I already have the 7.4 hardened push rods so can I just shim the rockers and I'm good to go right ?
Is there any negative effect or anything I better to know when doing this?
Nothing popped up on my search, MTI sells shims. It looks like lots of people are going to be running milled AFR's so might as well get this answered. Yes I know you have to measure and ideally use a pushrod checker and whatever but the bottom line is math says the head is .040 lower so I'm just going by the math here.
My gasket is going from stock (.054) thickness to .045
My cam is an MTI C1 Lunati grind which obviously has a smaller base circle HENCE the hardened 7.4 pushrods went in when I put the cam in. So now that my head is effectivley .040 lower than before here is my question.......
I already have the 7.4 hardened push rods so can I just shim the rockers and I'm good to go right ?
Is there any negative effect or anything I better to know when doing this?
Nothing popped up on my search, MTI sells shims. It looks like lots of people are going to be running milled AFR's so might as well get this answered. Yes I know you have to measure and ideally use a pushrod checker and whatever but the bottom line is math says the head is .040 lower so I'm just going by the math here.
Since the base circle (diameter) of your cam is .030 less than stock your 7.400 PR's were actually .015 too short (1/2 the diameter difference) for your application. It didn't matter because the lifter absorbed it. However with your heads shaved and thinner gasket bringing the head .040 closer ,the PR's are now .025 too long. (.040 too long - .015 too short already = .025 shim) This should bring the preload and geometry back in spec.
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Originally Posted by DAPSUPRSLO
Tony, in my case more shims moved the rocker tip closer to the intake side of the valve. I have T&D shaft rockers but it shouldn't make a difference.
Tony M.
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Aftica, thanks that what I was looking for and you did the math too.
Lastley, where to buy the correct shim material and size wize (Home Depo) and how exactly to install them.
This is only to make sure the "swipe" pattern is good to go. Nothing to do with pre-load.
If anybody wants to make me feel warm and fuzzy about P/V clearance please do. I am not flycutting.
Thanks, PDD is your car all together now ?
*EDIT* Aftica, stock LS1 pushrods are 7.38 I believe.
Lastley, where to buy the correct shim material and size wize (Home Depo) and how exactly to install them.
This is only to make sure the "swipe" pattern is good to go. Nothing to do with pre-load.
If anybody wants to make me feel warm and fuzzy about P/V clearance please do. I am not flycutting.
Thanks, PDD is your car all together now ?
*EDIT* Aftica, stock LS1 pushrods are 7.38 I believe.
Last edited by Mirek; 01-28-2005 at 03:06 PM. Reason: More Info
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Tony, the fulcrum height accounting for the moving of the tip in relation to being higher or lower makes perfect since. Good explanation. I was deffinately a little confused. I would guess this. If the fulcrum point is moving higher and was already higher to start with then the plane of the valve stem tip and retainer then it will pull it back toward the intake. If you are moving a fulcrum that is lower to start with then the plane of the valve stem tip upward then it would move it toward the exhaust side.
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Originally Posted by Mirek
Thanks, PDD is your car all together now ?
.
.
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Originally Posted by DAPSUPRSLO
Tony, the fulcrum height accounting for the moving of the tip in relation to being higher or lower makes perfect since. Good explanation. I was deffinately a little confused. I would guess this. If the fulcrum point is moving higher and was already higher to start with then the plane of the valve stem tip and retainer then it will pull it back toward the intake. If you are moving a fulcrum that is lower to start with then the plane of the valve stem tip upward then it would move it toward the exhaust side.
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I'm using the Morel lifters, and when doing the 22ft lb's and go method, I had 1 1/2 turns past zero lash. I did not want that much preload. After shimming, I ended up with 1/2 turn past zero, which is where I wanted to be. I probablly could have ran 1 1/2 turns fine, but to much pre-load can rob HP.
Tony, The engine is on a stand, so I'll go do the test you described. I'll report back in a minute......
Tony, The engine is on a stand, so I'll go do the test you described. I'll report back in a minute......