Vortec Heads Suck...

[SunSoaked]

oil past the valve seals?

Here's the deal:

Noticed a misfire at idle. Started pulling plugs to look for clues. #1=good. #3= oil fouled! Bingo. But the question is why?
This is a new gm crate motor with about 2k miles on it. I swapped new GM Vortec heads on it 1000 miles ago.

So I cleaned the plug with acetone and a wire brush. Swapped plug #1 with plug #3. Drove it for two days. Today I pulled the plugs and #3 is getting oil fouled again (originally plug #1).

Concluded it's not the plug. Inspected and ohmed the plug wires (new Moroso 8 mm low ohm). Wires are good. Swapped in a brand new spare cap, rotor and coil.

Gonna drive it a few days and pull the plugs again. If #3 us going south again I can conclude it's not the ignition.

Therefore, I'm assuming it can only be the valve guide seals or piston rings?

What say you all? I never even looked closely at the valve guide "umbrella" seals. I'm just assuming they have them?
Am I missing something here? I'm having a hard time believing that a new engine would have this condition.

I was hoping I just had a plug go bad but the problem didn't follow the 1-3 cylinder swap.