Rocker arm pedistal help
09-17-2009, 12:19 AM
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Rocker arm pedistal help Hi guys, I just registered so i will have to get around to a introduction and updating my profile. I just got a 2000 camaro with a forged ls6 in it. I am in the process of doing heads/cam for it. When I was taking the heads apart, I pulled the rocker arm pedistal up and there were these little rectangle spacers underneath. The heads I pulled off that they were on were 853's. The new heads I put on are LQ9's and I cant continue my install untill I know if I need to reuse them or not. Does anyone know? because it doesn't seem like the ls1's have them. I can already foresee what a pain they are going to be if I need to reuse them. Thanks for the help
09-17-2009, 12:32 AM
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LSxGuy widda 9sec Mustang
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Those are rocker arm shims (Small block ford) that some people use to fine-tune the rocker arm geometry and/or lifter preload. You will need to measure pushrod length or preload without the shims to determine what to do next. Those are probably .030" thick shims I'd think. What length pushrods are in it now?
There are a few writeups on checking pushrod length around.
There are a few writeups on checking pushrod length around.
09-17-2009, 12:46 AM
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Those are rocker arm shims (Small block ford) that some people use to fine-tune the rocker arm geometry and/or lifter preload. You will need to measure pushrod length or preload without the shims to determine what to do next. Those are probably .030" thick shims I'd think. What length pushrods are in it now?
There are a few writeups on checking pushrod length around.
There are a few writeups on checking pushrod length around.
09-17-2009, 01:06 AM
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LSxGuy widda 9sec Mustang
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I think I would be ditching the shims. With so many components changed, you are basically starting over on pushrod length/geometry. 7.4" is a pretty average length of pushrod, and probably right, but you do need to check it to verify.
Put the #1 piston at TDC [top dead center] of the firing stroke. If you loosely install the #1 rocker arms or hold pressure against the pushrods you can watch the valve events, as you rotate the engine clockwise the intake rocker will open and close, when the #1 piston reaches TDC after the intake closes, you are at the firing position for #1 cylinder and both lifters are guaranteed to be on the base circle of the camshaft from which you measure pushrod length and/or lifter preload.
You can do this two ways, I prefer to use a dial indicator for measurements, but with the new pushrods installed on cyl #1; hand tighten the rocker arms until you feel light load against the bolt, the extra lash should be now adjusted out of the valvetrain and the rockers will only have side-to-side movement (as long as the pushrods are long enough).
With the slack adjusted out, but no load against the lifter plungers, you can measure the pushrod side of the rocker with a dial indicator as you tighten down the rocker arms. From 0 lash until the rocker bolt is torqued and the lifter is settled in, that measurement is your preload. Depending on which lifters you use, the ideal preload can vary anywhere from .010" to .100".
Now if you don't have a dial indicator or adjustable pushrod length checker, you can count each 1/4 turn of the rocker bolt from 0 lash until the rocker bolt is torqued and have a somewhat approximate preload value. This is not exact, but you can get really close, usually close enough with stock or stock replacement lifters as these have a wide range of travel adjustment.
Each 1/4 turn of the stock rocker bolt is about .0125", actually a tad more than that due to the rocker ratio, but for estimation purposes is close enough. So lets say from 0 lash you turn the rocker bolt about SIX 1/4 turns: 6 x .0125" = .075" of preload, or if you turned the rocker bolt 1 full turn, it would be: 4 x .0125" = .050" of preload.
If you are out of range for preload too high, you can get shorter pushrods in .025" increments, or if you don't have enough, you can get longer pushrods. If you find out you need longer or shorter, TS would probably swap you out for the next size up or down.
Put the #1 piston at TDC [top dead center] of the firing stroke. If you loosely install the #1 rocker arms or hold pressure against the pushrods you can watch the valve events, as you rotate the engine clockwise the intake rocker will open and close, when the #1 piston reaches TDC after the intake closes, you are at the firing position for #1 cylinder and both lifters are guaranteed to be on the base circle of the camshaft from which you measure pushrod length and/or lifter preload.
You can do this two ways, I prefer to use a dial indicator for measurements, but with the new pushrods installed on cyl #1; hand tighten the rocker arms until you feel light load against the bolt, the extra lash should be now adjusted out of the valvetrain and the rockers will only have side-to-side movement (as long as the pushrods are long enough).
With the slack adjusted out, but no load against the lifter plungers, you can measure the pushrod side of the rocker with a dial indicator as you tighten down the rocker arms. From 0 lash until the rocker bolt is torqued and the lifter is settled in, that measurement is your preload. Depending on which lifters you use, the ideal preload can vary anywhere from .010" to .100".
Now if you don't have a dial indicator or adjustable pushrod length checker, you can count each 1/4 turn of the rocker bolt from 0 lash until the rocker bolt is torqued and have a somewhat approximate preload value. This is not exact, but you can get really close, usually close enough with stock or stock replacement lifters as these have a wide range of travel adjustment.
Each 1/4 turn of the stock rocker bolt is about .0125", actually a tad more than that due to the rocker ratio, but for estimation purposes is close enough. So lets say from 0 lash you turn the rocker bolt about SIX 1/4 turns: 6 x .0125" = .075" of preload, or if you turned the rocker bolt 1 full turn, it would be: 4 x .0125" = .050" of preload.
If you are out of range for preload too high, you can get shorter pushrods in .025" increments, or if you don't have enough, you can get longer pushrods. If you find out you need longer or shorter, TS would probably swap you out for the next size up or down.
09-17-2009, 07:30 AM
#5
On the LS1 with fixed fulcrum rockers, the pushrod length doesn't set rocker geometry or wipe pattern. That is set with shims. Looks to me that someone took the time to correctly setup the previous cam/head components. Don't throw them away. First check geometry on the new heads. If you need shims you have them. Only after the geometry is correctly set up do you measure for pushrod length. These are separate steps. Shims are not used to setup lifter preload, the pushrod length does that.
