Valve adjustment basics for 2V
Valve adjustment basics for 2V and 4V cars:
All 2V shims/applications are the same diameter, but larger than the 4V shims...
2v shims are the same as Fiat
All 4V shims/applications are the same diameter, but small than the 2V shims...
4V shims may be the same as Volvo
One shim per bucket...and always replace with new.
Most OE shims (2V or 4V) will be 3.85-4.05mm from the factory. Shims come in increments of .05 mm (.002"), but should always be measured (new and old) to verify actual size.
Exhaust valves tend to tighten...intakes tend to loosen. Clearance can be set to the loose end on specs for exhaust...and mid-range, if possible for the intakes. There is no reason to deviate from factory specs.
I'm not in favor of ever grinding a shim, as they are surface hardened...and any angular misalignment between the cam and the bucket can result in very expensive cam wear. (I've seen the results of an ejected shims, due to grinding...major cam damage!
In theory, one could measure the clearance, determine the new shim size...and find out that the new shim is now on the tight end of the range, and out of spec.
The safest way to do a valve adjustment is to measure, determine your needs...and order extra shims in the size you need (as the same marked size can vary in thickness)...and order shims plus or minus one size of what you think you need.
I had intended on writing a valve adjustment procedure over the Winter, as my BB will be due for its first service then....
Measuring the clearances: Engine cold. Lobe should be perpendicular to the bucket..Using a feeler gauge .001" thicker, verify no-go. Using a feeler gauge speced at the minimum thickness, verify "go", with light drag on the feeler. If both conditions are OK, clearance is fine. Always inspect cam lobes for sharp edges on the "ramp"...
Only do one lobe at a time and don't turn the engine without a shim in place...as lobe damage can occur. Personally, after I replace a shim, I turn the engine over once or twice to ensure that the shim is completely seated...then recheck the clearance. The easiest way to do this is with a remote starter harness (hooks across the started solenoid.)
Example:
Spec: .012"-014" Exhaust valve
Measure: .011" (too tight by .001")
Shim: 4.85mm (marked, not measured)
(.05mm=.002")
New shim: 4.80mm (marked, not measured)
If marked=measured...New valve clearance=.013"
No real need to beat yourself up, trying to hit 014" on the money.
Shims are ordered and supplied using the metric numbers...
Regards,
David