Posted by Chris Case [75.36.44.142] on Monday, March 18, 2013 at 20:33:42 :
In Reply to: Re: Compression tests posted by Mike Stone in Idaho [71.39.211.42] on Monday, March 18, 2013 at 19:13:58 :
Well, first, if the dry compression is good and even, there is absolutely no reason to do a wet test.
YES, wet compression will be higher, you have just increased the compression ratio by the amount of oil you squirted in. How much higher depends on how much oil- did you squirt in the EXACT same amount in each hole? Was each piston low enough in it's travel that no oil went straight out a valve? Has each piston traveled EXACTLY the same number of strokes to disperse the EXACT same amount of oil?
My feeling is that wet tests are done mostly by mechanics who want to sell a bottom end in addition to a valve job.
Here's my own criteria for rings-
a) lots of blowby, probably rings.
b) Blow-by puffing like a locomotive going up hill, rings fersure.
Poor oil consumption is as likely to be valve guides as rings, so you can't go by that re: ring wear. Guides will cause smoke while coasting down hill. Ring wear shows as BLUE smoke when you jump on it after coasting- the rings load up with oil during high vacuum coast, then burn all that oil when you hit the throttle.
Otherwise, if it has a bad valve, the head has to come off. Check for taper at that time. If good, fix the valves, put the head back on and run it. The usual cause of a complete rebuild is a crank and bearing shot, ot excess taper.