Leakdown test discussion, with 'strange' readings

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jos51700

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So over the last week, I went out to visit my dad. He's hardcore into the Chevy third-gen 6 cylinders of the '60s. I know, this is Mopar land but he's not online and I'm not about to sign up on a Chevy page just for this question.

His primary truck is a '66 4wd with a 292 that was rebuilt two years ago. I'm going to guess about 10k on the rebuild, 90% of that is highway miles at 55mph. It's got a Clifford intake, headers, and some kind of truck cam. Cranking compression is 185 across the board.

After going to Minnesota, this thing turned into an oil-burner. This was probably 5000 miles after the rebuild. It may have burned oil before that. No smoke, it's all going out the breather. So we did a leakdown test, and ALL the air is lost out the breather.
Cylinder 6 was the only normal cylinder at 5% leakdown.
Cylinder 2 and 4 were about 70-75%
Cylinders 1, 3, and 5, all started at 75%, but as the air increased (as I opened the regulator to push up to 100psi), they'd 'jump' to 25% and hold there.

When cross-examined about it, pops said simply, "I installed the rings with the dots up. Isn't that how they're supposed to be oriented?"

I don't do a lot of rebuilds and am wondering if maybe he got a set racing rings that only seat at WFO, if he's installed some upside down, or if they're breaking or something? Block was bored .060 over by a Longmont Colorado machinist. He's looking for the receipt, once the anger subsides.

What sayeth FABO?
 
Well there's only so many ways that cylinder pressure gets to a crankcase. Rings, busted pistons, what it all means is tear it down. It has been a long LONG time since I've re-ringed an engine. CAST IRON RINGS is all I ever used to use.
 
Simple question but I gotta ask,,When he installed the rings did he turn the gaps away from each other ?
 
Simple question but I gotta ask,,When he installed the rings did he turn the gaps away from each other ?

Knowing pops, those ring gaps were either precisely 120 degrees from one another, or lined up straighter than a laser beam. I'll ask him, although I know from personal experience that unless pinned (like on 2-strokes) the rings will rotate as the engine runs.
 
Affirmed, gaps were evenly spaced.

I'm curious why the leakdown reading would jump like that as the pressure goes up.
 
did he use cast rings? with 185 psi pressure he should be using a higher grade of fuel if not he could have broken top rings
 
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