340 Static Compression Numbers and Test Procedure

If you really want to know the compression ratio don't rule out using a whistler. Often times race track tech officials (circle tracks) will either have or have access to a whistler and for a small fee they might be coaxed into checking your compression ratio for you. I have one at the dyno and if used properly they are pretty accurate. Another benefit is that you only have to remove a sparkplug to use it.