Help with low compression numbers

Hi, we have a 1990 5.8 ford unknown hrs.
I did a comp test on all 8 cylinders today (engine was cold) if that matters?
I opened carb and with all 8 plugs removed battery a little on the weak side if that matters?
1=110 5=100
2=120 6=80
3=110 7=110
4=110 8=120
I've never had any problem with water in cyl. and plugs looked pretty good.
These comp numbers all seem low can this be from cold engine? I've drained the block for winter and pulled hoses so starting it was out of the question. I figured cold or not the reading would still be viable being I was mainly looking for consistancy. Do you think the 80psi in #6 constitutes a tear down this winter?

Re: Help with low compression numbers

Since you can't run it, a leakdown test is your next step to find out what the problem is. Don't just take it apart unless you know why. If it isn't obvious, you may have to put it back together to find out what the problem is.
Doing a compression test with a weak battery doesn't help
There are requirements to get good informantion from tests. If you don't crank the engine fast enough, you don't know if you have a good test or not.

Re: Help with low compression numbers

Ok thanks for the input I'll charge up the battery and try again with good cranking power. My Cobra manual says 25% variance but I'd much rather see no less then 15% which seems to be the least acceptable, depending on what source of information your going by.

Re: Help with low compression numbers

Don, I put my charger on and the battery was up near full charge,so I pulled my starter and it wa in sorry looking condition, on the outside anyhow. The alluminum brush cover and nose piece are corroded and anything steel all rusted up. I totally dismantled the unit (used factory manual) and dumped a 1/4lb of rust and dried up mud out of it, I cleaned everything up and all the thrust washers, brushes, springs ect. cleaned up nice, I hit the armature shaft with with a green scotchbrite and it also shined up nice, I reasembled the starter and used triple guard on the splines and bearings, installed the starter back in the hole and gave it a spin, All I can say it WOW it never cranked like that before, very peppy, turns the motor twice as fast, I did compression on a couple random cylinders and found the numbers greatly improved to 160ish, I'm going to wait till I have the motor up and running before I go through all 8 again just so I can get everything warmed up like the book says, I want to get it right next time. Until then I'm going to dissasemble the starter again and bead blast the housings paint and seal it all up, I'm confident threre's not a thing wrong with this starter it was just all gunked up inside.