lack of compression

[grey boy]

hi guys im a rookie to renovating landies and am hoping that somebody may be able to help i am restoring my 2a ute and currently working on 2.25 engine i checked all cylinders for compression first 3 came up trumps but 4th nothing so removed head to find piston looked good as did bore filled pot so to speak with kero which it held for over 4 hours so i was happy rings are good so has anybody got any clues please :)

[JDNSW]

Have a look at the valves - it may have simply been a bit of carbon under a valve or even an incorrectly adjusted tappet, but more likely a valve needs reseating or possibly is sticking (or both). It is unlikely that lack of compression results from anything except the piston/cylinder seal or the valve/valve seat seal. Loss of compression through leaking headgasket or cracked head or block is possible, but it would be very unusual for this not to be immediately obvious when the head is removed.

It could have been useful to test before taking the head off - turning the engine by hand and listening to the manifolds and crankcase breather in turn will usually give a noticeable hissing to show whether the leak is piston rings, intake or exhaust.

Hope this helps,

John

[davrac]

Check for a burnt valve (usually exhaust).

If the valves look ok I would suspect that the tappet adjustment was to tight. Generally as the valves and valve seat wear the valve clearance gets smaller until eventually it just will not close all of the way (again usually exhaust wears faster) and this will then cause the valve to burn.

Can also get a carbon build up in the valve guide causing valve to stick and no close all of the way. Put this together with a worn valve seat in the head and = no compression.

I would try putting a bit of kero around your valves or into the ports of the cyl without compression. with the valve fully closed it should hold reasonably well.

Good Luck

Hope this helps:D

[grey boy]

thank you guys ill check carefully everything you have suggested
:)

[Blknight.aus]

if the engine hasnt been turned in a while it may also be the valve guide sticking from gummed oil.

since its off it would be prudent to drop the valves out of it and give the head a good clean up and new valve stem seals.