setting lifter preload
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New User
Joined: Sep 2003
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From: TYLER, TX
setting lifter preload
Hey guys, I am installing pedestal mounted Ford Motorsport roller rockers in my 351C. New Crane cam, lifters, and valve springs. I also bought the shim kit for them. My question is how do I know if the shim is needed during the installation and how do I know which shim to use. There are 2 thickness sizes, .030 and .060.
Thanks for all the help so far. You guys are great!!
Thanks for all the help so far. You guys are great!!
Lead Driver
Joined: Nov 2000
Posts: 6,636
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From: Albuquerque
setting lifter preload
If you have pedestal mounts or adapter mounts there wont be any place for the shims. They are for the sled type. As I recall (double check this) You need about .030 preload. With the valve closed rotate the push rod with your fingers while tightening the adjuster nut. when you feel it touch the lifter tighten down another 3/4 to 1 1/4 turn. Then lock the poly nut.
Posting Guru
Joined: Aug 2000
Posts: 1,127
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From: (near) Denver USA
setting lifter preload
You can use shims between the fulcrum and pedestal on any pedestal-mount rockers.
If your lifters are not stock or OEM type, check the instructions that came with them to find the recommended preload. Many aftermarket lifters require less preload than the OEM type.
To check preload, install the rocker and pushrod on a valve that's closed (i.e., with the lifter on the base circle of the cam lobe).
As you slowly tighten the rocker bolt, twirl the pushrod with your fingers until you feel it bind. Turn the rocker bolt back and forth a little while twisting the pushrod to find the exact point at which all slack is taken up.
Once you find that point, you are at zero preload. Use a depth gauge (like on the end of a dial caliper) to measure the distance from the top of the lifter piston to the top of the lifter body.
Now finish tightening the rocker bolt down to the torque spec (18-22 ft lbs). Measure the lifter piston depth again and subtract your first measurement. That's the preload.
If the preload needs to be less, install the appropriate shim(s) to reduce preload. Shims reduce lifter preload by 1:1, an 0.060" shim reduces preload by 0.060".
If you need more preload, you'll have to get shorter pushrods.
If your lifters are not stock or OEM type, check the instructions that came with them to find the recommended preload. Many aftermarket lifters require less preload than the OEM type.
To check preload, install the rocker and pushrod on a valve that's closed (i.e., with the lifter on the base circle of the cam lobe).
As you slowly tighten the rocker bolt, twirl the pushrod with your fingers until you feel it bind. Turn the rocker bolt back and forth a little while twisting the pushrod to find the exact point at which all slack is taken up.
Once you find that point, you are at zero preload. Use a depth gauge (like on the end of a dial caliper) to measure the distance from the top of the lifter piston to the top of the lifter body.
Now finish tightening the rocker bolt down to the torque spec (18-22 ft lbs). Measure the lifter piston depth again and subtract your first measurement. That's the preload.
If the preload needs to be less, install the appropriate shim(s) to reduce preload. Shims reduce lifter preload by 1:1, an 0.060" shim reduces preload by 0.060".
If you need more preload, you'll have to get shorter pushrods.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
setting lifter preload
It is time consuming which is why many people do not do it and then have problems later.
If you know your thread pitch on the hold down bolts you can measure the pre load indirectly by counting turns on the bolt.
If you know your thread pitch on the hold down bolts you can measure the pre load indirectly by counting turns on the bolt.
Cross-Country
Joined: Apr 2003
Posts: 52
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setting lifter preload
I use FMS rollers on a newly rebuilt cleveland. I had some block decking (about .010) and the heads needed about .007 to make them flat again. I use the .030 shim on mine with stock length push rods.
Steve
Steve
Posting Guru
Joined: Aug 2000
Posts: 1,127
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From: (near) Denver USA
setting lifter preload
OK, just noticed an error in my previous post.
That should be longer pushrods.
If you need more preload, you'll have to get longer pushrods.
If you need more preload, you'll have to get shorter pushrods.
If you need more preload, you'll have to get longer pushrods.
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Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
setting lifter preload
The bolt for the rockers is a 5/16-18 thread so every turn is 0.055" or 1/4 turn would be about 0.014". If you wanted to just keep it in round numbers a half turn would be equivalent to a 0.030 shim and a full turn would be a 0.060 shim, -close enuf...
The preload applied would be about twice the measured distance at the bolt. In other words if you had to turn the bolt 1/2 turn from the friction point to seat it you would be applying about 0.055" of preload to the lifter. There is actually some math to do here with the 1.73:1 ratio rocker arms but my brain is too tired to do it now.
The preload applied would be about twice the measured distance at the bolt. In other words if you had to turn the bolt 1/2 turn from the friction point to seat it you would be applying about 0.055" of preload to the lifter. There is actually some math to do here with the 1.73:1 ratio rocker arms but my brain is too tired to do it now.
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Thread Starter
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New User
Joined: Sep 2003
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From: TYLER, TX
setting lifter preload
Eric,
I understand about the thread counting and turns, but since these are still pedestal mounted rockers, I believe there is no adjustment. I may be wrong about this, but I believe Bubba is right. I have to use shims or longer pushrods and just torque the rocker bolt to specs.
Just wanted you guys to know that I have looked at some other forums and this one is by far the best I have seen. The technical knowledge here and explanations are great.
Thanks to all!!
I understand about the thread counting and turns, but since these are still pedestal mounted rockers, I believe there is no adjustment. I may be wrong about this, but I believe Bubba is right. I have to use shims or longer pushrods and just torque the rocker bolt to specs.
Just wanted you guys to know that I have looked at some other forums and this one is by far the best I have seen. The technical knowledge here and explanations are great.
Thanks to all!!
Elder User
Joined: Jun 2003
Posts: 886
Likes: 1
From: Houston/Hope BC
setting lifter preload
Alternate method for measuring preload:
On valve in question, rotate to backside of lobe with valve train assembled and torqued. Lay a quality straight edge along the top of the head surface where the valve cover mates. Mark (do not scribe) a line with a fine line Sharpie brand pen. (on a dry clean push rod, of course.) Relax rocker arm nut until pushrod no longer moves upward. Scribe a second line. Measure this distance with your dial caliper from edge to edge. This assumes, of course you have some pre-load to begin with, which is normally the case, as after a valve jobe the valves have receded deeper into the head. I have yet to need a longer pushrod on a re-build, but this may not be the case for you. Yes, is is a pain, but do it twice once you have the lines drawn and verify they hit the same. It is a snap ofter that to bring them into range. Check them again after the adjustment. Good luck.
On valve in question, rotate to backside of lobe with valve train assembled and torqued. Lay a quality straight edge along the top of the head surface where the valve cover mates. Mark (do not scribe) a line with a fine line Sharpie brand pen. (on a dry clean push rod, of course.) Relax rocker arm nut until pushrod no longer moves upward. Scribe a second line. Measure this distance with your dial caliper from edge to edge. This assumes, of course you have some pre-load to begin with, which is normally the case, as after a valve jobe the valves have receded deeper into the head. I have yet to need a longer pushrod on a re-build, but this may not be the case for you. Yes, is is a pain, but do it twice once you have the lines drawn and verify they hit the same. It is a snap ofter that to bring them into range. Check them again after the adjustment. Good luck.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
setting lifter preload
Thanks macguyver, brbeat1 obviously didn't get what I was talking about. It is an alternative to pulling the manifold. You can also use a magnetic base indicator to measure the preload directly from on top.
I have a set of scorpion pedestal mount roller rockers for my engine. I also will be running roller lifters. My entire valve train will be blueprinted, I just don't bolt parts on. You can't get a FE block to turn 9000 rpms day after day like I did if you just bolt stuff on blindly.
I have a set of scorpion pedestal mount roller rockers for my engine. I also will be running roller lifters. My entire valve train will be blueprinted, I just don't bolt parts on. You can't get a FE block to turn 9000 rpms day after day like I did if you just bolt stuff on blindly.
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New User
Joined: Sep 2003
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From: TYLER, TX
setting lifter preload
Thanks for all the replies and help. Sorry I misunderstood you Torque1st. I will begin assembly in the next few days. If I have any more questions, I know I can depend on you guys for the answers.
Thanks again,
Bobby
Thanks again,
Bobby
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