81 XJ550 Valve Shims

Hi all,
I’m hoping somebody can double check my math on this, as it’s my first time making a valve adjustment.

1981 550 w 9k miles and I’m assuming the valve shims have never been changed.

Cyl 1 intake measured .0015 with Y280 shim
Exhaust measured .004 with Y275 shim

Cyl 2 is .0025 with Y270 shim
Exhaust is .004 with Y285 shim

Cyl 3 intake is .003 with an unmarked shim:/ not sure what that means
Exhaust is .004 with Y285 shim

Cyl 4 intake is .0025 with a Y27C shim. Idk why it has the other letter. But assuming y275?
exhaust is .004 and Y285 shim

Conversion table here for inches to mm
.0015in = .038mm
.0025in= .063mm
.003in = .076mm
.004in = .10mm
.005in = .127mm

so using the chart I found following the guide in the overload hour, I’m thinking I’ll need
C1 270 intake and 265 ex
C2 265 intake and 275 ex
C3 265 intake and 280 ex
C4 270 intake and 280 ex

Am I close? The valves seem super tight when I measured the clearance with the camlobe top center.

Also are the spec’s supposed to be different from intake to exhaust? They are according to the chart I used.

thanks for any help!!

 

Get yourself a micrometer or borrow one so you can actually measure the intake shims for cyl. 3 and 4 before making any decisions. Also it is better to use actual metric feelers to take the measure the gaps.

 

Thanks for the info. Micrometer is a good idea. Wish I did that when I had them out already. lol.
And the feeler I used was labeled for both metric and inch