Armin,
The exhaust valve side clearance of 1.96 mm is about right.
Is the intake side clearance similar?
This may seem like a lot but this is suitable considering some day it may be run with worn valve guides.
During test-assembly, measuring the valve-to-piston clearance with the cams properly timed is critical.
Be aware that this clearance needs to be confirmed either side of TDC overlap as the piston ‘chases’ the valve closed in some situations (usually with very ‘wild’ cams).
Are these original
Ate valves?
Spec for original exhaust valves is 40.0 ± 0.1 mm (intake 46.0 ± 0.1 mm).
I have never seen them out of spec too-large.
The head appears to have recent machine work on the cylinder seating surface.
It is wise to measure the heads to see how much metal was removed.
There is potential interference between the head and piston at the corner (red arrow) of this cut.
Is the surface (green double arrow) the same depth as the (yellow double arrow) cut?
Has the surface (teal arrow) been cut?
The carbon marks on the (yellow arrow) surface appear to be exhaust blowing past a gasket.
Be sure this surface is ‘true’.
If the heads have been (undocumented) modified, you must pay careful attention to
every detail.
How do the valves and valve guides measure?
Yes, that is a 2.2/2.4 head gasket and matching cut head.
Check the gasket in the top of the cylinder and in the head.
Measuring the piston-to-cylinder clearance is quite an ‘art’ and requires the exact ‘right’ tools.
The measurement is complicated by tapered and out-of-round cylinders and tapered and otherwise shaped pistons.
The key is to set a bore gauge in the cylinder and then use a micrometer to measure the difference to the piston – or vice versa.
There has been a lot of discussion about this.
After you have cleaned, lubed and installed new points in the distributor, run it in on a distributor machine for several hours.
Document the advance from static to 3000 (distributor) rpm.
With these numbers, you can set the static timing before you start the engine and the 6000 (engine) rpm timing will be exceedingly close to the intended number.
After the engine has ‘run-in’ a bit, always final check the 6000 rpm timing with a strobe light.
The nice aspect of the 911 project is you can pause at almost any step.
Take a deep breath.
Proceed when the enthusiasm strikes.
Think how much fun it will be when finished.
Best,
Grady