Help! need a 0.160 thick x 1.06 dia. shim
 

I'm working on getting the shims corrected on a built motor that I purchased. I can find all the shims I need except one: a 0.160" thick x 1.06" dia shim.

This is an oddball size not carried by mazda or mazdaspeed.

Does anyone know where I can purchase a shim of these dimensions? I'm even having trouble finding a local machine shop that will make one. In that regard, does anyone know the specific grade and hardness of steel used for shims?

Any help would be greatly appreciated. Thanks!

Your options would be tearing the motor apart to grind the tip of the valve to make the next size up shim fit with your desired clearance, or settle for a not so perfect shim clearance, or find somewhere that grinds shims down. you might have to call someone out of state

Grinding a shim down is not the problem. The shim I need is thicker than any I can find: 0.160 / ~4mm. I have thought about stacking two shims together, but someone told me that one of the stacked shims could go into the engine - which I don't see how.

The theory is that the lower shim raises the upper shim so much that it does not have sufficient engagement within the groove, and can potentially hop out of the lifter.

It won't "enter" the engine per se, it just won't be where it's supposed to be.

Does anybody make a lash cap to go between a stock valve and a stock lifter, as would be used in a shim-under-bucket design? Seems like that is what's called for here.

Or you could see if someone is willing to sell you a single lifter from a kit such as this: Supertech Cam Follower Lifter Miata

Buying a single SUB lifter from Mazda Motorsport is no problem (I had to get some extra...).

Are all the other shims close in thickness or is it just this one that is absurdly different?
If so, what's the reason (bent valve, etc etc)?

Thanks for the suggestions on the lash cap, sub lifter... - I will look into these options.

Nik - the engine was built with Supertech parts, including the head. They really messed up the shim tolerances. We have been able to get all the other shims worked out except for this one. There does not appear to be any bent valves..., and I can't say for sure why this one is so far off.

I'm curious about this myself.

Were the valve seats replaced when the head was rebuilt?

The proper way to fix it is to have the valve and seat resurfaced on the offending valve.

Yes - a complete Belfab valve spring kit was used (Springs, Titanium Retainer, and Seats) when I bought the "built" motor.

I'm hoping I can just use a combo of lash cap + shim to make up the 0.160 needed.

No, not the spring seats, the valve seats. The pieces shaped like little cock rings that are press-fit into the combustion-chamber side of the head, against which the valve face seals.

In this image, it's the part which is sort of copper-colored:

https://www.miataturbo.net/attachmen...1&d=1370033782

Assuming that the tip of the valve stem itself was not ground down intentionally, the symptoms you are describing sound typical of what happens after a valve seat is replaced, but it not properly cut down to the correct depth.

Sorry, I misunderstood. I'll have to check on the valve seats. It would not surprise me in the least if you are correct.

Having the valve seat cut and the valve properly seated is not that big of a deal. I am somewhat suspicious that a mistake was made in the valve job, or lack thereof. Just like Joe is alluding to.

It's also entirely possible that the valve itself is just too short. If you do pull the head, it wouldn't hurt to (temporarily) swap it with another valve and see whether the problem follows the valve or stays with that location in the head.

This will give you a good indication of where the problem lies, and where the corrective action needs to occur.

IF the valve itself is too short, then you can just replace the one valve (and re-lap it into the seat), saving time and money relative to having the valve seat re-ground.

I appreciate the info guys. It's good to know the options on table and the potential specifics to the problem.