OldGray320i
OldGray320i Dork
2/20/20 7:31 p.m.

Ok, on a few of my valves, I've got clearances that are larger than the factoy shims can cover - apparently 3.3mm is as big as you get (or that Mazda specs), and I need several 3.4 or larger.  

Not sure how that happens, but I can stick between a .015 and a .021  between a few of these things. Not easily, but they go in between the shim and the lobe (easily might be taking it .002 smaller; and, measurements converted to mm to see about shims)

Do I have worn shim buckets or something?

Or do I need to re-measure where a lighter touch is used to get the feeler in?  I typically go up a step until I can't get it in, and I'll keep using a stout push until it won't go. 

This project is giving me fits, just when I think I've turned the corner, something else seems a little out of kilter.

Vigo
Vigo MegaDork
2/20/20 9:21 p.m.

.021 is a pretty stiff feeler gauge, so you can force that into something that's not .021 when one side of it will move (valvespring).  If the head has ever had a valve job done it's possible a shop could have machined the 'tip height/stem height' wrong and made the clearance too large. Usually that grinding is done because if you machine the valve face or the valve seat you end up moving the whole valve up in the head and shrinking all your clearances so you grind on the top of the valve to compensate. If the head has never ever been worked on you might just be pushing too hard. 

OldGray320i
OldGray320i Dork
2/20/20 10:47 p.m.

 Don't believe the motor has been apart, started at .012 and went up from there, I'll go back and measure at "reasonable pressure" - work back  through those.

Seems odd...

frenchyd
frenchyd PowerDork
2/21/20 6:40 a.m.

In reply to OldGray320i :

The feeler gauge should just slide in with a light resistance. You probably are opening the valve.  
 Valve springs on overhead camshaft engines are much, much, softer  than on pushrod engines. Without having to overcome the mass/ resistance of a rocker arm and pushrod  they can be softer and still not float at high rpm. 

dculberson
dculberson MegaDork
2/21/20 7:23 a.m.

It's been a few years since I've checked valve clearance with a shim and bucket setup but I think there should be basically no resistance. 

OldGray320i
OldGray320i Dork
2/21/20 9:55 a.m.

Re-measure coming up, thank you gentlemen. 

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