I have seen many of you on here talking about doing cams and changing valve springs, but what do you mean when you say you have double shimmed? Where do you get the shims? How do you install? and where do they go?
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I have seen many of you on here talking about doing cams and changing valve springs, but what do you mean when you say you have double shimmed? Where do you get the shims? How do you install? and where do they go?
Hi DaveVQ, double shim mean that you put 2 shim under the spring, they go one on top of each other, doing that will make the spring a little more stiffer, you can order the HR from Dave Burnett 512-444-1400
If you want to double shim you need to order 48 shim, I believe I paid like .92 cents each. The installation is pretty strait forward, as you put both shim first, then the spring, then the hat and the lock and finally the the bucket goes on top. You need a special tool from snap-on to install/remove the lock on top of the hat: http://buy1.snapon.com/catalog/OBJECTS/49900/49889.JPG
The org term "double shim" originated back when SR20DEN first posted the data comparing different valve spring stiffnesses at various lifts. Not only was the HR spring much stiffer than other OEM springs at high valve lifts, it didn't bind until 13mm of lift (compared to 11mm stockers and 12mm nismo). This led him to remark that even if you used cams with 11mm of lift, you could still preload the springs by 1mm w/out introducing bind for a total of 12mm of effective seat pressure at maximum valve lift. He used the term "double shim" and people took this and ran with it...
So if you are running 11mm lift cams, one 1mm "shim" (or two .5mm) is appropriate. I definitely wouldn't run two 1mm shims lest the springs bind.
And depending on one's setup, "shimming" can be unnecessary altogether.
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The org term "double shim" originated back when SR20DEN first posted the data comparing different valve spring stiffnesses at various lifts. Not only was the HR spring much stiffer than other OEM springs at high valve lifts, it didn't bind until 13mm of lift (compared to 11mm stockers and 12mm nismo). This led him to remark that even if you used cams with 11mm of lift, you could still preload the springs by 1mm w/out introducing bind for a total of 12mm of effective seat pressure at maximum valve lift. He used the term "double shim" and people took this and ran with it...
So if you are running 11mm lift cams, one 1mm "shim" (or two .5mm) is appropriate. I definitely wouldn't run two 1mm shims lest the springs bind.
And depending on one's setup, "shimming" can be unnecessary altogether.
Very interesting infos... How can we precisely measure the cam lift ? I'll be running VQ35 cam with my DEK...
Yep I was going to post saying IIRC VQ spring seat washers (what we've called shims) are 1 mm nominal thickness, but I see doublea has already got that covered.
So if you are "double shimming" HR springs you will indeed have 2mm (nominal) of thickness under the spring, reducing the install height by 1 mm from stock.
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