Valve Spring Shims

[GTSspeed]

So I'm rebuilding my head (RB20 and yes I'm months behind haha) and I started looking into shims for the stock valve springs. I pulled all my springs and I can tell that some are stiffer than others. I've been doing some research and it seems that I don't need to spend the big bucks on Tomei springs if I keep things reasonable (250-275 whp). However, I'd like to be able to push things higher without re-doing the head work. If this wasn't the case then I likely wouldn't bother with the shims. Should reduce valve float and even out the spring forces, right?

Please correct me if I am wrong...

Also, what is the best approach to sizing/matching shims. My approach was to determine all the spring stiffnesses by placing a weight on each spring and measuring the deflection (F=kx). I figure that the stiffest springs don't need to be shimmed (or shim slightly to bump up the preload) and shim all the others in increasing amounts.

My questions are as follows:

1) Can I just purchase new OEM valve springs and make things easy?
2) How much are the valve springs compressed under normal conditions? How much force is generated? (This counts as one, don't be smart haha)
3) What size are the valve spring seats in the RB20 head? (Mine won't come out real nice for some reason)
4) What thickness of shims should I be looking for and what increments are normally used between springs? (0.2mm shims and no more than 3 shims for any valve??)

I've done a little research and I can't seem to find much information on this. I don't think it's too common and maybe I don't even need to do it. Just looking to reburbish the head. After 170,000km it's well needed.

[derk]

id you're not planning on running high lift cams, or dont plan on revving past the stock rev limit, then you dont really need to change the springs.

hp doesnt really have any correlation to what springs you run, the cams and rpm's dictate whether you need springs or not.

[derbeck]

sorry brother it doesnt really work like that our cars as you probably know are a pain in the ass to set the heads im using the rb26 270 cams with 10.25 lift... assemble the head find out the space between the cam and the bucket at the given cam position( may not be the lowest part of the lobe) measure between with a thickness guage and find the thickness becarefull not to forget to check how far the valve will drop as you dont want to hit a piston. parts can be ordered from rhdjapan.com but take a little time to get to you.. good luck

[nelsonmxmarc]

? Shims? they're hydraulic lifters. All you need to worry about is cam lift and what spring's to run with said lift.

You don't need springs for mild cams, but in some instances (for the obvious reason that they're 20 years old), it's best to upgrade to prevent any slack in the lope of the cam.

[derbeck]

I was unaware they are hydraulic much easier

[GTSspeed]

So maybe I should ask more specific questions then:

If I'm using the stock springs then I just need to use the stock valve seats (which preload the springs once installed). Right?

If I purchase new springs (such as Tomei), would I still use the stock seats or different thickness ones? Nelson?

Thanks for the discussion.