On my 460, I have the symptoms of a bent/broken intake valve. Compression does not register on that cyl. all others between 155-168. The piston IS moving as it should, air can be felt through the plug hole, just not with much force when it is plugged with my finger. Air whistles out the throttle body when I blow it into the CC. I also has a significant ticking/tapping sound at all rpm consistant with the valve train speed. When I unhook the fuel injector, little change is noted. Vacuum is fairly solid, only jumping a pound or two at idle, and not measureably above idle. It runs good, and I really don't want to tear into it right now. I would like to drive it a few hundred miles or so. Is this safe? All the other plugs looked rich, so I assume they are gettiing a little mixture from the bad cyl. I am afraid the computer will sense the overall richness, lean out the mixture, making 7 good, and one really lean. Should I unhook the injector, or just run it? Or not run it at all? If I do fix it now, I will only do one head, if I fix it later, I will do both. Thanks, Chuck

 

sounds more like a bent or broken rocker arm to me ( a bent valve should make the vacumn jump all over the place) pull the valve cover, and see, and no I wouldn't drive it. if it is a bent valve you could break it off, and destroy the piston, block and the head. if it is a rocker or pushrod you could push the lifter out, and loose alot of oil preasure.