compression test vs leak down test

[lewis_willy2]

http://www.dietersmotorsports.com/Co...akdowntest.htm

ok guys i seem to a little bit of low compression in one of my cylinders.

1 - 135
2 - 150
3 - 155
4 - 155

no cylinder 1 seems a little low. i have been advised to do a leak down test and listen to where the air is escaping from, as in the article above to prove where the problem lies.

now it has also been mentioned that i could do a compression test with oil in the bores. what is the theory behind this?

i havent got a leak down tester at the mo, so the oil in the bores and a compression test is my next stage. can someone explain exactly how this is to be done?

just to clarify this is on my williams turbo. i thought it was my turbo but upon inspection the turbo is in great condition. and with the turbo removed the blue smoke is still very much there after about 10 seconds of running. and relatively thick.

before putting in the pistons and rings i glazed the bores. the pistons i bought had already covered little bit of mileage so i am pretty certain that my problem probably lies in the rings?

the car has not yet been run for longer than a minute at the max. roughly around 8-10 times. so 8-10minutes of running, is this long enough. and am i panicking over something that may be cured with a bit of proper running time?

a great long post so if you got to the bottom then thanks for ready and if you have any suggestions thanks again

lewis

[MAXIBOY]

rings need at least a 100 miles to bed in.

the theory of a few drops of oil is that it seals the rings better...so if you add a squirt and the compression goes up its a ring/bore fault. if it doesn't it a valve fault.

you need to run the engine under load to force the rings out onto the bores so they can bed in.

also what oil are you using to run the engine in on.

[Coops]

as neil says mate, the oil will seal the rings providing a spike in comp reading if its knackered rings

if not then its probably a mis-seated valve and stem seal

[lewis_willy2]

do you think i should be worried?

the compression isnt that low is it. think i should just get my intercooler pipework sorted and get it on the road.

its just running standard oil at the mo to keep it lubed up while sitting cant remember what grade. wot oil should i put in it?

[Coops]

running in oil or mineral 15-40, nice coarse cheap oil to help the rings bed in

and yes i'd stick it on the road, run it in properly and see, lots of engine braking and dont take it on boost for first few hundred miles, see how it goes