need to do the compression check tom to decide what to do. what should it be at? (stock) this will determin if i re-build it or not 
compression?
- Thread starter 88stangmangt
- Start date
im not real sure what stock would be, and it is tough to compare sometimes as people dont test the same (all plugs pulled, warm notor, throttle wide open, etc). more important, IMHO, is consistent numbers across the board (less than 10% deviation), and wet and dry being close together (bigger the difference, the more the rings are shot).
it seems like people have anywhere from ~120 to 180 psi. anything over 150 on a mill with some miles seems to be well thought of (based on posts in here).
good luck.
it seems like people have anywhere from ~120 to 180 psi. anything over 150 on a mill with some miles seems to be well thought of (based on posts in here).
good luck.
NKau
Founding Member
You should check a manual or something, but I think you want to see it below 110? What usually determines if you want to rebuild or not is the variances in the compression numbers you get on each cylinder. You shouldn't get 95 on one cylinder and then 130 on another; they should all be fairly close, like between 10 of each other. There's an actual percentage listed in the haynes/chilton saying how close the numbers should be. Post your numbers and someone can help you out.
ok will do just got to find a store that has one (maybe a loaner) any one know? pepboys,autozone? i know summit sells them but i dont want to wait that long.
local parts stores sell them. good thing to own, IMHO. under 30 bucks.
i think NKau meant to say the numbers should be over 110. the higher, generally, the better (sometimes excessive deposits, etc can artificially raise compression too much, where detonation and preignition (carbon glows, acting like a plug) become problems.
good luck. as said, just post what you get and many will comment (best to post wet and dry numbers).
i think NKau meant to say the numbers should be over 110. the higher, generally, the better (sometimes excessive deposits, etc can artificially raise compression too much, where detonation and preignition (carbon glows, acting like a plug) become problems.
good luck. as said, just post what you get and many will comment (best to post wet and dry numbers).
first you do a dry test. just screw the hose into the plug hole and crank. then you pour a little bit of oil into the plug hole (just a little; teaspoon or so.) then redo the compression test. the oil helps to seal the piston rings, so if the number goes up substantially, this suggests that the rings are losing some compression. if the number stays the same, but say for instance, the number is low, that suggests that the valves, etc are at fault. at this point, a leakdown test is informative.
i like to do both wet and dry just to see what happens and have two sets of numbers to compare. if you are just playing around, a dry test should be fine. just an option. good luck.
i like to do both wet and dry just to see what happens and have two sets of numbers to compare. if you are just playing around, a dry test should be fine. just an option. good luck.
