I pulled the head off to fix an exhaust leak. I could not get 54 year old bolts out due to rust. Prior to this, it was getting hard to start and would pop through the carb. I put the head back on and now I have 2 cylinders with no compression. The middle 2 cylinders near the intake crossover. I think I put the wrong intake gasket on because because I had to pull the gasket off and put on what appears to be the correct one. There’s no water mixing with the oil and I have spark to all plugs from the distributor. Did I burn the exhaust valves. ?