After all the troubleshooting with my Dad's 65 Mustang, and the weird issue at the last post, it turns out the pistons had a bunch of carbon buildup on the top and the rings got stuck to the piston grooves and both the pistons cylinder bores got all scored up. All the cylinders on one side are at about 90psi except #1 which had 0. The heads are OK. The car is getting a new short block. The theory we have is that the PCV system is not in place or failed. I know we have a hose going from the filler on one valve cover straight to the throttle body. I read this post, https://stangnet.com/mustang-forums/threads/new-5-0-build-pcv-breather-both-or.925401/ and it sounds like that is only part of the setup. The PCV also has a valve at the back of the intake? Point me in the right direction, guys. This new engine and labor is set my Dad back $6000. I do not what this to happen again. The car is still in the shop, so I can't look at it easily but I can go there to look.