Question

I am stumped, have done a dozen head rebuilds and have never experienced near zero compression on all five cylinders. Triple checked head and did a leak down test. and all checked out. Set timing up with cam lock tool, spot on, and what is strange is I get 15lb. from cylinder one, and when I apply air I see slight bleed over to cylinder three. Cylinder two bleeds over to four, and only five does not bleed over to other cylinders. Five has 30lbs., so I did wet test with oil in cylinders, helped ever so slightly, so I am stumped, any ideas.

I picked this up and owner had exhaust cam oil seal leak, a friend of owner did repair, but could not get it running. When I got it I found timing out and VVT cam bolt not properly torqued. So I checked compression, it was the same as it is now. I pulled head assuming valves were wiped out, but they were not, did a leak down, all was fine, but there were dings in piston tops. So that is the back story, seems I have exactly the same problem after rebuilding head. What else could cause no compression?  Cylinder walls looked fine, I cleaned piston tops, and sprayed oil to keep from rusting as head was off for a few weeks, but covered, didn't see any seepage of oil down pistons. No visible cracks. Engine was running before oil seal job. Any ideas?  

Thanks, 

Vehicle
Odometer
156000

Answers

If there were dings in the piston tops, the valves might have hit them at some point.  If you've rebuilt the head, it should be fine, but it's also possible that the cylinder walls are scored.  Was there any coolant in the oil?  Also, if the compression is that low, your piston rings are probably damaged in some way.  If compression is leaking into other cylinders, the block might be cracked.  Have a machine shop look at the cylinder walls, and have them look at the water jackets too.