It appears to be low all the time. I bought the car in June, and it was well checked out, with no sign of this problem then - I certainly understand about the expense. By the way, that info I found about the front valves being the possible culprit, was on the Star Motors sight in their published troubleshooting guide - I take it they are a very reliable source of info, but have no references with regard to that.
Francis E. Abate
1970 300 SEL 6.3