Cylinder compression leak-down tester

[1969Mk3Spitfire]

Does anyone have any experience of using this test, if so, what for and was it helpful and informative?

Any recommendation of a Brand? They are plentiful on ebay for around £25......any good for occasional use?

I'm trying to track down a sooty plug issue.

[Pete Lewis]

well  can be useful   but a normal compression test would give you good results but if an oil control ring has failed i doubt either would show that up 

if the compression rings were all Ok  you get correct compression but wont remove oil from the bore 

 

have you tried a colour tune  if there is oil in the burn you get a good flash of yellow showing up ????

Pete

[johny]

Cant see any advantage of a leak down tester (uses compressed air supply to pressurise cylinder) over a conventional compression tester except that you would need the first if for some reason you cant spin the engine over on its starter motor. Surely the latter should give a more accurate idea of the engine condition as its in movement plus of course it doesnt require an air supply...

With a compression tester the accuracy (so quality and price) isnt that important as youre comparing cylinder readings as much as anything.

[Wagger]

You are gonna get the same people (including me) repeating themselves. It sounds like your plug is sooting up due to oil in the chamber. The cheap checks are to see if you can wag the inlet valve fom side to side when it is closed with the rocker box off. That will identify a worn vave guide. If you can see the guide, start up and observe if it is sliding up and down. That will identify if it is loose. If it is loose or worn, then oil will be sucked in every time the valve opens.

If those tests yield nothing, then it requires head and sump removed in order to remove the piston and examine the oil control ring. The state of the bores and combustion chambers should reveal differences.

A temporary fix may be to fit a different grade of plug on that cylinder. One that gets hotter. I cannot remember which way the numbers go but I know that N4's were hotter that N5's on my bikes.

This is a tedious problem and I do sympathise having had a similar experience recently.