Compression

So I am running a compression check on the '74 that has been Chevroned and it occoured to me that I have never held the throttle open when cranking the engine over. Well hey Elvis, now my compression is where the previous owner said that it was....

210 holy cow.

And straight across the board, this reading is after five revolutions on the cranking...

So, why does it make a difference holding the throttle open?

And anyone else out there have any idea what the compresion ratio may be with that kind of reading? (Ballpark ofcourse...)

Thanks all, hope the holidays is treating you well.

Wish me luck, I battle Chevron tomorrow on the gas thing....

Bri