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I just did a rebuild on my engine and started doing a little diagnosis due to how it was running. I dropped the pan and noticed # 3 cylinder bottom side is bone dry. I had the head rebuilt by a machine shop if that helps. There is also oil coming to number 3 spark hole. compression is reading about 100 which is too low.
 

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I just did a rebuild on my engine and started doing a little diagnosis due to how it was running. I dropped the pan and noticed # 3 cylinder bottom side is bone dry.
Didn't you say, in another post, that the #3 rod bearing had seized? Bottom of piston and lower cylinder walls receive oiling and cooling from squirt hole in the rod. Seized/spun rod bearing = plugged squirt hole = no oil.
I had the head rebuilt by a machine shop if that helps. There is also oil coming to number 3 spark hole.
PCV valve dumps into #3 intake runner. It gets all the crankcase blowby oil from bad rings and worn cylinders.
compression is reading about 100 which is too low.
=improper test procedure, head gasket problem, rings not seated, scored cylinder walls, rings installed wrong, valves improperly adjusted, cam out of time, etc.
I've seen 1.3s with over 125k miles that still have over 160psi.
When assembling your motor, it has to be clean, clean , clean!
I'm thinking from other problems you had (spun bearing), debris was left in the crank/block from machining.
If you spend less time assembling the engine components, than cleaning them, you're probably doing it right.
 

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Is this the same engine?
Is this after a second rebuild?
What was done after you found the seized #3 rod bearing?

If the engine has not been reassembled with the original problem corrected, the same blocked oil way that probably caused the failure of the #3 rod bearing would also have caused a lack of lube to the walls of the #3 cylinder.

Assuming this is after the engine has been reassembled, the point made by Azelgin on the rod drilling needs to be checked, however, the fact that you have oil above the #3 piston and none below may also point to a ring installation issue - the second ring has a tapered face, if this ring is installed upside down it will scrape oil upwards into the combustion chamber.

Regarding the low compression - it's not unusual to have low compression on a newly rebuilt engine - especially after a re-bore/re-ring - the rings need to seat before they will seal properly - but - again as Azelgin has pointed out - there are other possible causes for low compression.
 
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