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Gtr Shim And Valve Stem Diameter?

StavrosRB2630

By StavrosRB2630,
in Engines & Forced Induction

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StavrosRB2630 Apprentice

StavrosRB2630

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Basicly a cam manufacturer (im in the UK) are planning to re-grind my cams to a different spec, and rather than just use bigger shims as they thought would cause too much mechanical drag (or something!) they wanted to add something to the bottom of the buckets as well.

Must admit im not 100% what he meant as i was trying to hear him in a busy office.

If this dont make sence to anyone i may need to ring him back and get a more detailed explanation!

SteveL Mentor

SteveL

Posted
Posted
Basicly a cam manufacturer (im in the UK) are planning to re-grind my cams to a different spec, and rather than just use bigger shims as they thought would cause too much mechanical drag (or something!) they wanted to add something to the bottom of the buckets as well.

Sounds like they want to make more $$ out of you for custom work. AFAIC the 'drag' will be more or less the same, but lift rates will change placing extra load on the springs. Don't understand why you would bother adding extra to the bottom of the buckets when increasing shim thickness has the same effect.

For an R32 GTR, valve stem diameter is 6mm for inlet and 7mm for ex., but there is a small tolerance, off course. I have some spare shims so will check diam for you.

proengines Rising Star

proengines

Posted
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The shims are 12.3mm diameter. The exhaust valve is nominal 7mm on the stem but is reduced down to 6mm from just below the collet area to the tip of the valve, so the caps and collets are the same on inlet and exhaust. It's around 1.9mm from the top of the collets to the tip of the valve.

Depending on the thickness of shim and bucket you require you could run a toyota solid bucket, as fitted to the late 2jz and 1zz engines. You can buy them in increments, I dont have the minimum or maximum thickness here though. They are the same diameter as a 26 bucket and you dont have to worry about shims at all. They are a little fiddly to set but once they are done you dont have to worry about them any more.

StavrosRB2630 Apprentice

StavrosRB2630

Posted
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SteveL- No, as they doing it all for free :P

There was a reason, but it was when they thought the shim was above the buckets, soon as realised the cam dont operate directly onto the shim it didnt matter.

Dont think it was drag, cant remember the exact reason, but either way its irrelivant when the shim is below the buckets.

Cheers for the measurments, just happened i got them off another source this morining actually anyhow, but thanks all the same :P

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