3.8 valve clearances

I am rebuilding my reconditioned 3.8 head off my mk2. I am fitting higher lift, longer duration cams (Rob Beere Racing, fast road, RBCSU). Valve clearance specs are .008 inlets, .010 exhaust.

Inlets are all .008 thou apart from one which is a slightly tight .009
Exhausts are between .011 and .013.

Should I go with these gaps or strive for perfection and get new shims for the 7 that are not quite there?

Or should I run the engine for a few hundred miles and see if the valves settle in to the valve seats a little (It has new seats and valves).

Thanks in advance for your advice.


If the machining work was done well, the new seats don’t settle much. After CJ rebuilt my head with new everything, a few gaps change by no more that .001 over the first 10k miles. Mine is always set dead on spec. I would hesitate to set it far out just because it “might” change. If you assemble it with Cometic gaskets, it’s not a huge chore to pull the covers to check it after it’s run for a while.

After 10-15k miles w standard cams, new valves & guides, .060" seat width my exhaust clearances closed up by .001". Intake remained as set.
I started at .008" so exhaust all still good at or around .007". Left them all alone.
Intakes still at .005-6"

More or less my experience, on multiple
XK engines.

When I set the clearance, I always went with .006/.008, in/ex.

Noise increase was minimal and it extended readjustment periods.

Looks like I will be redoing the exhausts then. I think I can swap a few of the shims around and just buy a couple more new.