More confused than ever....spring shim question
07-22-2009, 12:45 AM
#1
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More confused than ever....spring shim question So i have a custom cam 236 236 610 610 on a 113+3 and i have a set of the blue strip .625 918 springs. I installed it all about two weeks ago and just waiting to haul it down to get a tune. Well i thought i had all bases covered but it seems that your are supposed to check the installed height. I read about this before that the 918 springs do not require shims but the more i read it seams like i should have checked it. In one thread i read they install right at 1.8. So my question is should i check it. I would think since i am running a cam that is .015 away from max of the springs there would be no room for shimming. Am i right or wrong here? It runs good and sounds good, but i dont want any problem. And i know that some 918s are rated to .600 but these were rated to .625 and are not from the bad batch. I am not going to rev it out to 7000, prolly going to stay under 6500
07-22-2009, 10:31 AM
#5
Just check it. It's peace of mind. If it's too tight, you could break all the springs or pull the rocker bosses out of the head and possibly destroy the entire motor. Too loose, and the springs won't be able to control the valve as well, and you'll just hit valvefloat sooner. Then again, it may be fine. You won't know until it's checked.
07-22-2009, 10:56 AM
#6
Check it if you dont want to put a new motor in it down the road...sooner than later.
You COULD let it right and it MIGHT be fine, but it also might NOT be fine and break a spring at 6600 RPM's and take out the whole block after it drops a valve...not a pretty sight.
The way I do it that makes it very easy, is to take a coat hanger and cut a chunk of it out on the straight side. Use a digitial micrometer and measure it/mark it at what the installed height should be. Its easier to cut it longer and use a grinder to gradually bring it down to the correct height.
Then you can just remove the spring and stick the coat hanger in there and it should fit with no play up and down.
This is how I do it on the 565 in the race car with more open spring pressure than these average cammed LS1's use closed.
You COULD let it right and it MIGHT be fine, but it also might NOT be fine and break a spring at 6600 RPM's and take out the whole block after it drops a valve...not a pretty sight.
The way I do it that makes it very easy, is to take a coat hanger and cut a chunk of it out on the straight side. Use a digitial micrometer and measure it/mark it at what the installed height should be. Its easier to cut it longer and use a grinder to gradually bring it down to the correct height.
Then you can just remove the spring and stick the coat hanger in there and it should fit with no play up and down.
This is how I do it on the 565 in the race car with more open spring pressure than these average cammed LS1's use closed.