Just rebuilt my 68 225 (All stock rebuild) and adjusted the valves after startup while hot. When should I adjust them again? How long does it normally take the valves to seat in?

usclstaffingnet@sprintmail.com

The critical factor here is correct lifter break-in with the cam. It comes down to several factors like running time and how you drive. There really is no hard and fast rule as every scenario plays out differently. If it were up to me, I would readjust by 2500 miles or even sooner. You will get an idea of how things are going by how much adjustment you need. I would repeat this once again by 10,000 miles. You should find the when cam breaks in, you will require less adjustment over time. There is a clearance ramp ground into the lobes and you do not want the adjustment to go too far out because you want to keep the valve opening event on the ramp. Once the cam is properly broken in, once a year should be fine.

Mitch

m5black@aol.com

This is one of those "it depends" kind of questions.
One of the factors is how close you got the lash setting during the first adjustment.
I tend to run a new engine through a few "heat cycles" and re-check / re-adjust the valves a few times before the valve cover goes on.
Once on the road, I do not take the cover back off unless I hear a noisy valve or I detect a low rpm miss and real quite lash. (usually both)

I would say that after 1000 to 2000 miles, it is time to go back in for a check. If there is no major change in the settings, you should be good for at least a year or two.
Note that if your head does not have hardened exhaust valve seats, you should check more often. Exhaust valve lash that tightens-up over use is a sign of valve seat recession.
DD