weird compression results - 4age

[levinguy]

did a compression test on a silvertop yesterday
first try i got 20,0,0,0

this was with throttles open, cranking fine etc.
ok not good, put some oil down the plugs tried again
got something like 50,0,0,20
next try 50,50,50,50

eventually they all got up to around where they should be and were pretty even, can't remember exactly 200 and something psi

so i can only put it down to the engine sitting around for a while?
should i be worried that there was no compression to start with?
or will it be fine?

never encounted something like this before..

thanks

[~SlideWays~]

Run the engine until it is up to temp, then try again. The first test was most likely due to cold pistons (heat = metal expanding = rings seal better).

Or you have a poltergeist.

[levinguy]

engines out of the car,

and i doubt the pistons would have heated up to go from 20,0,0,0 to 200+psi on all four just by cranking it over on the starter motor?

[strx7]

how long has the engine been sitting un-run? We have this issue ourselves some of the motors we have on our shelves can sit for upto 5 years between being run up and being sold, generally, they have lowish compression but with a good run the compression will come up, alot of it we put down to, oxidisation on the valves and valve seats etc.

[levinguy]

quite a while, not sure but proberly over a year

have the engines ran fine that have had the same problem strx7?

Thanks,

[hsmidy]

if the engine had been running in a car before hand with a few k's on the clock (nothing outragous) and has been left to sit for some time then its not uncommon for the piston rings to become kind of carbon locked which will give you very low compression.