Valve shims when is it needed?
06-03-2008, 09:46 PM
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Valve shims when is it needed? How much can the installed height be off before being deemed shimworthy? I just bought some Patriot Golds for my 5.3 heads. I have researched the installed height needs to be 1.800. I used an installed height checker (not sure of it's proper name LOL) and came up with the following measurements. Spring seat,retainer and locks all in place for these of course.
Intakes
1= 1.806 / 2= 1.803 / 3= 1.806 / 4= 1.807
5= 1.805 / 6= 1.805 / 7= 1.808 / 8= 1.805
exhuasts
1= 1.812 / 2= 1.812 / 3= 1.817 / 4= 1.812
5= 1.813 / 6= 1.812 / 7= 1.817 / 8= 1.814
The intakes sit a bit closer to the 1.800 overall than the exhuasts. I am going with a G5X4 camshaft the springs are rated to 650 lift so I would think I have a good .030 worth of room before the .050 before coil bind measurement is reached. Should I shim any of these? Thanks in advance.
Intakes
1= 1.806 / 2= 1.803 / 3= 1.806 / 4= 1.807
5= 1.805 / 6= 1.805 / 7= 1.808 / 8= 1.805
exhuasts
1= 1.812 / 2= 1.812 / 3= 1.817 / 4= 1.812
5= 1.813 / 6= 1.812 / 7= 1.817 / 8= 1.814
The intakes sit a bit closer to the 1.800 overall than the exhuasts. I am going with a G5X4 camshaft the springs are rated to 650 lift so I would think I have a good .030 worth of room before the .050 before coil bind measurement is reached. Should I shim any of these? Thanks in advance.
06-04-2008, 05:17 AM
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Vettenuts should I use a spring tester? I can get a mini spring tester and determine spring PSI at the different heights. What would be a recommended PSI needed to sustain lets say 7K rpm . PSI needed open and closed?
06-04-2008, 07:16 AM
#5
I have tested several sets of springs (not Patriot, but PSI and COMP) and found them to be right on the money with what they advertise for spring stiffness and 1.800 values. I would think LG can supply the required spring forces since its their cam, but I like to have about 140# on the seat to prevent bounce. In your case, you will be less due to your current installed height. (I don't remember the Patriot Gold spring values, but if you have them its a simple calc.). You then need to calculate how much clearance you will have and distance between the retainer and seal to make sure all will clear.
