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Old 09-17-2003, 06:59 PM   #1
Zio
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Join Date: Jun 2001
Location: alsip,IL,60803
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How to set valve spring height?

Ok guys I know how to put on and take of the valve springs but setting the height has me a little lost. First of all how do i know what size shims i need. Where can i get these shims? What tool do i need to measure the height and where can i get it? how is the height excatly meaured?

Sorry for all the queestions. I searched but didn't find all the answers that i wanted.

thanks
Tom
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Old 09-17-2003, 07:25 PM   #2
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First of all, you set spring height by knowing what pressure you want on the valve seat when the valve is closed, and open. If you know what springs you have, you can look at a chart that lists spring pressure at different compressed lengths. You select the installed height that will give you the correct spring pressure for your setup.

Then, you use an installed height micrometer to measure the distance from the spring seat to the retainer with the valve closed. The shim height is the difference between the measured distance and the installed height you select from the chart.

In short:
Select the spring pressure, measure the installed height and shim to that pressure.
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Old 09-17-2003, 08:33 PM   #3
Zio
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ok I have a few more questions

I got my springs from combination motorsports. Do i call them to find out what height i should install them at? does it go by what springs i have or a combinations of what springs and cam i have?

Would i be able to pick up an install height micrometer at a parts store or would i probably have to order one?
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Old 09-18-2003, 11:26 PM   #4
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Quote:
Originally posted by nateh
... Select the spring pressure, measure the installed height and shim to that pressure.
What is the process of selecting spring pressure? Is it dependant on the valves?
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Old 09-19-2003, 08:13 AM   #5
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Spring pressure is more dependent on the cam requirements. The cam manufacturer would tell you the spring pressures that are appropriate for your application. It depends a lot on how high you're going to rev and the ramps on the cam. When I was looking at cams, for the most part they all liked to see about 120-130 lbs. on the seat and 320 or a little more open pressure, but there were some differences. The stock springs are weaker, and most stock replacements don't supply that much pressure. Find out from your cam manufacturer what pressure you should shoot for, and they would probably be able to recommend the proper springs as well. A place like Combination Motorsports can help as well.

Zio,
Find out from CM what the recommended height is. They give pretty good advice, so the springs will probably work if they knew when you purchased what valves and cam you're using. As for the micrometer, machine shops might have one. I had to order mine.
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Old 09-19-2003, 11:23 AM   #6
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What he said. CM will tell you what height for the springs for what cam. I just got their stock diameter springs that are good to .600 lift and they recommended a height of 1.760 which I accomplished using their -.030 locks. You can adjust the height using various methods, locks, different retainers, (usually titanium versions are thinner), and by using shims that are placed under the spring on the seat. Sam at CM sent me an assortment of locks, (-.060,-.030, STD, +.030), because I didn't know my installed height. I didn't have a spring micrometer but was able to use a set of dial calipers once I got a spring installed. BTW I thoroughy enjoyed taking the spring off and on with the heads on the car.... not! What a PITA. Having the right spring compressor would help a lot. The one from KD Tools seems to work if you're not removing your heads.
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Old 09-19-2003, 11:23 AM
 
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