So my bluetop 4AGE was being sluggish up until 3k rpm, after that it screamed like there was nothing wrong with it. So I checked the vacuum lines, exhaust, all kinds of simple thing that I could think of. Then me and my dad did a compression test, one of the cylinders had half as much compression as the others, and when you unplugged the spark wire from it, I wouldn't change the idle at all. But it wasn't the plug or the wire, cause we swapped those out too.

Long story short, we took the head off, head gasket was fine, everything inside was pretty clean minus a little carbon build up. Can anyone please help me??

Is this a high mileage motor? May want to go thru the valves, particularly to that one cylinder with low comp... Have the head sent out to the machine shop anyway to get looked at also. Have it pressure tested, milled..

Yeah it has 200k+ miles on it, currently trying to get everything cleaned up.

Since the motor's half apart, maybe nows the time to consider a rebuild?

do a leak down test to see if the rings are bad or its the head.

Wet compression test?

murdercrase wrote:Yeah it has 200k+ miles on it, currently trying to get everything cleaned up.

murdercrase=what does the cylinder walls look like, the low comp cylinder in particular? Any ridge at the top?

did you check your distributor rotor?