Head Shims - Any Pro's or Con's

[SKOLJACK]

Recently had my cyl. head machined .014" and installed a .020" head shim (recommended from the machine shop) along with new head bolts. Can I expect any advantages or disadvantages from this? I understand this may give a slightly lower compression ratio, but would I be running into any leakage problems when turning up the boost levels (15 -18 PSI)? Just wondering if anyone has experience with these (good or bad)?

 

[greycar]

I have absolutly no idea what a head shim is???????? can you please inform me??????

Or are they talking about shimming the springs??????????????

if they reconditioned your head and did proper valve job you can just slap her back together. Higher compression isn't bad and with .014 gone your valve reliefs still have room. Factory service manual will have all limits for machining, I don't know off the top of my head.

 

[Jehu]

Sounds like a thicker headgasket to me...Make sure you find out exactly what it is though...do they plan on adding a shim to the gasket???

 

[SKOLJACK]

You install a head shim in conjunction with a new (conventional) head gasket to regain proper valve train geometry & to lower compression or to return compression ratios back to stock. My only question is, is it safe to "crank" the boost up to 15 - 18 PSI with a head shim or are they more prone to leak or fail. I installed it exactly as the directions listed. They have been used on diesel engines, just wondering if anyone had experience with these shims on a 4G63.

Maybe I should of posted in the Extreme Tech Forum!!!

 

[greycar]

You can get the same with a proper valve job. And maybe you should check your limits once again. In my 26 years with being around cars I have never once heard of this option. And as a racer I would never use this option.

 

[Defiant]

You install a head shim in conjunction with a new (conventional) head gasket to regain proper valve train geometry & to lower compression or to return compression ratios back to stock.

Um... shaving a DSM DOHC head has no effect on the valvetrain geometry. It can have an effect on cam timing, but it won't be much.