Lifter preload?
Thread Starter
Former Vendor
Joined: Mar 2003
Posts: 18,666
Likes: 395
From: Tampa FL
St. Jude Donor '07-'08-'09-'10-'11-'12'-'13-'14-'15
Lifter preload?
I have asked and searched and keep coming up with different things. I need preload for the following
Comp XER 227/242 .610/.618 114 LSA
OEM LS3 lifters
OEM rockers arms with Comp trunion upgrade
OEM LS3 style heads milled to 64cc
Comp XER 227/242 .610/.618 114 LSA
OEM LS3 lifters
OEM rockers arms with Comp trunion upgrade
OEM LS3 style heads milled to 64cc
Le Mans Master
Joined: Aug 2005
Posts: 5,375
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From: CA.
St. Jude Donor '13-'14-'15
Well stock rockers arms have the "preload" preset -- tightening down the rocker bolts to the specified TQ should be all you need to do-They are NON adjustable
However with other than stock lifters and heads not 100% sure if you would be OK with that
I would be most concerned with pushrod length---If you had to re-size your pushrods to get the valve geometry correct-- Then maybe the preload would be off when torquing down the bolts----I would ask Comp cams for their opinion
However with other than stock lifters and heads not 100% sure if you would be OK with that
I would be most concerned with pushrod length---If you had to re-size your pushrods to get the valve geometry correct-- Then maybe the preload would be off when torquing down the bolts----I would ask Comp cams for their opinion
Safety Car
Joined: Apr 2010
Posts: 4,231
Likes: 451
From: Maryland
Dad said: If your going to do it, do it right.
When you change things the best way to get it "right" is to get a pushrod length checking tool, it's basically an adjustable pushrod, some you measure and some have built in read outs. It used to be between .025/.050 preload for most hyd. lifters with .030 being a good number but check with what is recommended for that "lifter".
Take all the clearance out with the cam on the base circle than add in the preload amount for the right length pushrods to order, but be sure that you are not preloading the lifter i.e. pushing down the cup in the lifter when you take that "0" clearance measurement. You usually only need to measure one.
PS: You can also take it down to "0" clearance than add in the preload amount remove the checking tool and that's what you order. I would do it both ways just to see if the results are in a few thousand's of one another.
Note: You don't need to worry about geometry with the stock shaft style mounted rocker arms unless you change the valve stem length by say sinking the valves deeper into the heads, etc. you just need to get the pushrod length right for the correct amount of preload.
Edit: If you are using the same thickness of head gasket and the cam is cut using the same size base circle as the stocker and wanted a "quick & dirty" answer to your question it would be whatever the amount was removed from the heads in thousands and just make the pushrods that much shorter and if the head gaskets are thinner or thicker than adjust for that too. Sometimes not that much is removed that you need to do anything as long as the preload is with in specs. That is why a pushrod length checker is a "good thing".
Take all the clearance out with the cam on the base circle than add in the preload amount for the right length pushrods to order, but be sure that you are not preloading the lifter i.e. pushing down the cup in the lifter when you take that "0" clearance measurement. You usually only need to measure one.
PS: You can also take it down to "0" clearance than add in the preload amount remove the checking tool and that's what you order. I would do it both ways just to see if the results are in a few thousand's of one another.
Note: You don't need to worry about geometry with the stock shaft style mounted rocker arms unless you change the valve stem length by say sinking the valves deeper into the heads, etc. you just need to get the pushrod length right for the correct amount of preload.
Edit: If you are using the same thickness of head gasket and the cam is cut using the same size base circle as the stocker and wanted a "quick & dirty" answer to your question it would be whatever the amount was removed from the heads in thousands and just make the pushrods that much shorter and if the head gaskets are thinner or thicker than adjust for that too. Sometimes not that much is removed that you need to do anything as long as the preload is with in specs. That is why a pushrod length checker is a "good thing".
Last edited by C7/Z06 Man; Dec 19, 2012 at 04:17 PM.
Tech Contributor
Joined: Dec 1999
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From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
When you change things the best way to get it "right" is to get a pushrod length checking tool, it's basically an adjustable pushrod, some you measure and some have built in read outs. It used to be between .025/.050 preload for most hyd. lifters with .030 being a good number but check with what is recommended for that "lifter".
Take all the clearance out with the cam on the base circle than add in the preload amount for the right length pushrods to order, but be sure that you are not preloading the lifter i.e. pushing down the cup in the lifter when you take that "0" clearance measurement. You usually only need to measure one.
PS: You can also take it down to "0" clearance than add in the preload amount remove the checking tool and that's what you order. I would do it both ways just to see if the results are in a few thousand's of one another.
Note: You don't need to worry about geometry with the stock shaft style mounted rocker arms unless you change the valve stem length by say sinking the valves deeper into the heads, etc. you just need to get the pushrod length right for the correct amount of preload.
Edit: If you are using the same thickness of head gasket and the cam is cut using the same size base circle as the stocker and wanted a "quick & dirty" answer to your question it would be whatever the amount was removed from the heads in thousands and just make the pushrods that much shorter and if the head gaskets are thinner or thicker than adjust for that too. Sometimes not that much is removed that you need to do anything as long as the preload is with in specs. That is why a pushrod length checker is a "good thing".
Take all the clearance out with the cam on the base circle than add in the preload amount for the right length pushrods to order, but be sure that you are not preloading the lifter i.e. pushing down the cup in the lifter when you take that "0" clearance measurement. You usually only need to measure one.
PS: You can also take it down to "0" clearance than add in the preload amount remove the checking tool and that's what you order. I would do it both ways just to see if the results are in a few thousand's of one another.
Note: You don't need to worry about geometry with the stock shaft style mounted rocker arms unless you change the valve stem length by say sinking the valves deeper into the heads, etc. you just need to get the pushrod length right for the correct amount of preload.
Edit: If you are using the same thickness of head gasket and the cam is cut using the same size base circle as the stocker and wanted a "quick & dirty" answer to your question it would be whatever the amount was removed from the heads in thousands and just make the pushrods that much shorter and if the head gaskets are thinner or thicker than adjust for that too. Sometimes not that much is removed that you need to do anything as long as the preload is with in specs. That is why a pushrod length checker is a "good thing".
Good info! Also recommend that you make SURE that you check and inspect the rocker pedestals for damage and wear. Make SURE that the area where the rockers sit in the pedestal are not worn enough to allow the rocker to twist left and right.
I Recently experienced a C5 with severely worn rocker pedestals which made the preload inconsistent and contributed to valve train noise.
My 02 ZO6 was valve train noise free and all of a sudden it has a slight noise. Got to rip it down this winter and thats the first thing that I’m going to check
!
Bill
Thread Starter
Former Vendor
Joined: Mar 2003
Posts: 18,666
Likes: 395
From: Tampa FL
St. Jude Donor '07-'08-'09-'10-'11-'12'-'13-'14-'15
Thanks for all the input guys. Since the base circle of the cam is smaller and the heads were milled approx .036 those two things may cancel each other out and the stock length or possible 7.375 is the ones to go with. Thanks so much
