Compression= 0
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Senior User
Joined: Sep 2003
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Compression= 0
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
Posting Guru
Joined: Sep 1999
Posts: 2,297
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From: Indiana
borin&strokin
Time for a leak down test.
When you say you can here air coming from the throttle body when you blow air into the clylinder. Is that with that cylinder on TDC where the valves are closed?
Time for a leak down test.
When you say you can here air coming from the throttle body when you blow air into the clylinder. Is that with that cylinder on TDC where the valves are closed?
New User
Joined: Feb 2004
Posts: 17
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From: tampa
I once had a similar problem with the eight cylinder on my truck, what had happened was ford put a vacum line pulling of th eight cylider and it over heats the valve, the guys a napa machine shop redrilled my plentum in the middle and plugged the orignal hole. That way it pulled even from from 4 cylinders on one side. if you pull everything off to change out a head you might as well take the other head off and have it checked, that way you only have to buy on gasket set and do the job once. I drove my truck forsevearal months on seven cylinder, well the 8th cylinder had about 40psi, but preferablly fix it asap.
