thought id share a good how to guide to doing what i am going to do. for checking valve clearence
What Tools Do I Need To Be Able To Do This?
This is one of the rare instances that only simple tools are required. Some considerations are necessary that if you plan ahead of time your process will be easier. Read the list of tools, the engine parts needed and their descriptions below:
Short block with at least one piston/rod assembly installed.
It is required that on engines such as the big block Chevy that has different handed pistons that you do at least two cylinders so as to verify each design.
The cylinder heads, with milling and valve job complete.
All modifications need to be completed on the cylinder heads you plan on testing. You may use the head with light pressure testing springs, but chamber volume, surfacing, valve job, and lash settings, etc., must me complete or you will need to re-test.
Cylinder head bolts or studs
Whether you are using bolts or studs as your cylinder head fasteners, you will need to have some available. You may use used fasteners for this test.
Head Gasket (preferably a used one for this test)
A compressed gasket (used) will be more accurate than a new head gasket.
Camshaft and specs for the cam you are using as well as what rocker arm ratio you intend to use.
You must know what your cam lift values are going to be with this combo. If you plan on possibly using multiple cams through the season, it would be best to test each one. If you plan on running a high ratio rocker arm, you need to test with that rocker arm on the cylinder head.
For cutting the modeling clay
You need to place modeling clay on the tops of the pistons. DO NOT use PlayDoh, it springs back after compression and will not be accurate. Modeling clay is available at most art stores and will be perfect for this exercise.
You need to torque the cylinder head to specified torque values.
Crank Turning Socket or other turning device
You will need to spin the engine and a crank turning socket is the easiest way to do this.
Dial Caliper or other "accurate" measuring device
After you have rotated the engine and removed the cylinder head ... you will cut the clay in various locations and then you will use the caliper to measure its thickness.
(this was found on http://www.centuryperformance.com/piston2valve.asp)