OldGray320i GRM+ Memberand Dork
2/15/20 10:14 p.m.

Ok, so taking valve clearance measurement on the old intake cam to get a baseline, and from the nose of the car at 1, successive lobes towards the fire wall as follows:


1  08
2  09
3  10
4  10
5  <8
6  09
7  10
8  10

From a quick look at Miata.net, for the intake cam they should all be between 8 and 9, right?

And to adjust, I need to know shim thickness, right?

Measured (bone) cold, lobes pointing straight up.

Question: as I go to drop the MSM cam in it, will any of that change?

Without yet looking,  torque sequence with cam caps, or as long as they're to spec, no bigs?

OldGray320i GRM+ Memberand Dork
2/15/20 11:02 p.m.

Found cam cap torque sequences...

codrus GRM+ Memberand UberDork
2/16/20 12:27 a.m.

Note that the English units spec in the manual is wrong in at least one instance (they converted it wrong or wrote it down wrong) and is rounded/truncated in others.  IMHO even if you have English feeler gauges, it's easier to convert your measurement to mm and then work in those units afterwards.  This is also useful because the replacement shims are spec'd in mm, so it's easier to figure out what to order.  I plan it out with a spreadsheet, using columns for these:

measured clearance (thou)

measured clearance (mm).  All measurements after this are in mm.

shim now (take the shim out and measure it)

total gap (shim + clearance)

spec min (out of the manual)

spec max (out of the manual)

minimum shim size (total gap minus spec max)

max shim size (total gap minus spec min)

And now you have the two values that the new shim needs to be between.  I keep track of all the shims I have available (the ones out of the engine, any spares, plus the sizes available to order) and figure out the one that'll give me the smallest gap within the spec.  I typically aim to have all the valves as close to the minimum gap as I can.

I've had people accuse me of being overly anal for the spreadsheet, saying it's easier to just swap a couple shims around.  To that I say maybe so, but I usually get it right the first time doing it this way.


OldGray320i GRM+ Memberand Dork
2/16/20 9:03 p.m.

Ok, so one of the shim buckets has a broken lip.

This is nuts...

Feels like it'll pull straight out, find a used one and swap, generically replaceable like the shims?

codrus GRM+ Memberand UberDork
2/17/20 9:16 a.m.

They pull straight out with a magnet, yes.  I don't see any reason why they shouldn't be interchangeable like that, but I've never tried it.

OldGray320i GRM+ Memberand Dork
2/17/20 9:40 p.m.

Ok, drop can in, does not want to spin freely. 

Half turn and it hangs. 

Torque sequence seems to be inside-center cap, to intake side, and clockwise in an outward pattern going to the end cam caps. 

Tips in cap tightening sequence to get it to spin?

codrus GRM+ Memberand UberDork
2/17/20 11:19 p.m.

The sequence you describe is the one I've always used.  I've never tried to install one without the valve springs and buckets installed though, so "freely spin" isn't something I've ever checked for.

I assume all the journals look OK, the new cam measures the same diameter as the old one, etc?



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