One head is 0.005 inch (0.125mm) lower than the other 2

[yelcab1]

I have a 72 911S engine with one head that is just a tad lower than the other two by 0.125mm. Is there any possibility of damaging the cam if I use it that way?

[icarp]

.0049" is a lot . I would think that will cause too much interference in the cam tower .
What makes a well built 911 engine is the art of getting all of the measurements in sync .
I would not allow that measurement to stand in one of my builds .
I hope this helps
Ian

[cgarr]

How are you measuring? Together on the engine? could be the case, cylinder or head that's off?

[r lane]

I remember a number of .003'' as the limit, but depends on how worn out are the cam shafts and housings. As stated above, in which piece does the problem lie. What ever, you need to fix that. Bows the housing, creates odd stresses and oil leaks.

[JoeMag]

i set them on a cylinder and measure to the cam tower sealing surface using a dial indicator. you don't get absolute thickness, just difference.

if that is really the case, you could get a 0.005" base cylinder shim for that head.

[911pcars]

Another option is to machine the remaining cylinder head mating surfaces so they all match. 0.0049” is barely renewing the mating/sealing surface. You also get a very slight bump in compression ratio. I’ve had all heads milled 0.040” to increase the CR, but you also have to take into consideration valve-to-piston clearance, valve lift, cam timing and any other “stack” mods (crankcase spigot, cylinder height).

Sherwood