you didn't have the valves/seats cut at the shop?

 

Head went untouched. Budget had to be set somewhere and that was it.

 

You're going to measure by using some arbitrary thickness but relatively thin shim as a nominal reference, & measure gaps with a feeler, right? I did the same, and a simple excel sheet saved me a ton of time. Make the 1st row for imputing the measured gap. make the 2nd row something like: = your reference shim thickness + (measured gap - desired gap). This should spit out the exact shim thickness you need for that valve as long as none of them need to be thinner than your reference. Better than back 'o napkin math...

also I made the mistake of measuring for shims before I lapped in valves, and it made enough of a difference to matter. My used head was pretty nasty though, so YMMV.

 

Well ****, I'm jealous. That's like $10k in plastic. lol.

 

Wackbard. Did you do it before or after putting the head on the block? Apparently torquing it down can change clearances.

 

... before... That's the first I've heard of it changing values. I just torqued down the cam caps when I did my measurements. If the values were changing significantly after torqueing down the head, wouldn't that imply that the whole head is flexing significantly when it's torqued to the block? That seems like it would be a design problem beyond just lifter clearance, but I'm just armchairing here.

 

Then how would a machine shop ever setup the head?

Same, make sure you torque per the sequence and use the same torque value each time.

 

I meant clearances on the bench vs on the block.

 

Can't say 100% as I'm still waiting on the stupid little dowels...

I did my valve lash because the shop was taking forever but he didn't mention anything about torquing the head down on the block when checking it. All I had the shop do was clean + recut seats + springs + retainers + seals. He was bitching about having to check/set lash so I paid for work to that point and measured & bought shims.

Hopefully, it'll get put back on the block this weekend. If the dowels show up...

 

Not sure I buy this. Torque plates are used because the bores can twist a little, maybe up to .001" or so, and you want to correct for that. That is a large void across a large distance. The head has a lot more support structure, and you're talking about a much smaller distance the deflection is being measured across, and there is a range of acceptable which is 2-4x that of the range of acceptable bore sizes. IOW, there's no way the clearances change enough to matter.

 

 

I set the valve lash on the bench, then later checked it on the car. No significant change.

--Ian

 

When you go to reassemble the head, I learned a good trick for getting your valve keepers back in: position the keepers with the spring uncompressed, slip a Ziploc bag over the top of the keepers, then compress the spring. The bag gets pinned by the spring compressor, and the tension of the plastic on the keepers nudges them right into place. you can get them to seat in about 5 seconds. Totally awesome hack.

 

Head is assembled. I have lots of pictures. Also started on the block. Can someone confirm these shims for me? Or suggest improvements? I'll place the order in the morning if I can find all of them.



I just stacked feeler gauges. So there is a good chance these are wrong. But its worth a shot.

 

Looks plausible to me. The spreadsheet I used is here:

http://www.codrus.com/miata/fm2r/valves-2014-2.xlsx

It's essentially the same, although I put more of the intermediate numbers on there and I only did intake (machine shop had done exhaust when they cleaned up the head).

--Ian

 

Im just over here takin notes and trying to learn.

 

I'd try remeasuring with a 1.3 shim to allow minimum feeler gauge stackup then order the rest.

I realize you want to get it done...

 

I'm going to do this when the shims come in. But I'd rather give it a shot. Doesn't hurt to have extra shims.

 

This is a money vs time tradeoff, yes.

--Ian

 

I'm going to assume high performance racing means like actual high performance racing. Not BP things.

So my bore is 3.3084".

Top ring: .0165 ≈ .017"
2nd ring: .0182 ≈ 0.19" (rounding up because bigger is better?)
Oil rail: .0496???

Should the oil rail gap be that much bigger than the ring gap?