measuring installed valve sping height

ive done a lot of stuff with cars without much equipment but i am putting a large cam in my 500 cadillac. i want to measure 2 things without taking the head off the car.
1 is installed valvespring height as am putting in higher rater springs and also want to make shure valve clearance is ok.
I have a good acurate caliper and have a good idea how to make shure i have valve clearance by finding tdc and measuring the distance the intake and exaust valve will move from closed before making contact with the piston( i am shure i have lots of clearance.
what is a easy way to measure installed valvespring height.
It doesnt have to be pefect just not too close, as installed pressures will be too high.
I thought i would take a small piece of rod and cut it the correct min installed height and use it as a guage .
any ideas
I

I'd use a valve spring height micrometer to get the correct measurement. They aren't that expensive....

i know waht your talking about i might have to track one down befor i start putting the thing together

ya gota remember that a caddys installed valvespring pressure is about 60 lbs, i can actually push them down by hand :LOL: :LOL: I am only going up to about 110 lbs

the package is for up to 6400 rpm cam i got , i am not planning for anything over 5000 to 5200 so we figure we can be a little looser and still stay a long way from float problems

Back a long time ago, I used to take a piece of 1/8 welding rod cut to the approximent length of the installed height. Just radius the ends as you bring it into final length. Use you digital caiper to get the finished size. It fits into narrow spaces easily.

The advantage of these are , cheap and very fixed size, it won't change unexpectedly while you are working, fits in tight spaces.