Slight misfire on cylinder 4

[tj350]

Hey guys, been fighting this problem for a while now I want to see if anyone else has dealt with this or has any ideas. I have a 1999 Tahoe with the 5.7 vortec. Bought it with a very slight misfire on cylinder 4. It’s only noticeable at idle causes a little vibration. The pcm has not thrown a code since I cleared it the first time but on the live misfire data I can see it misfiring.
Ignition and fueling have been gone through. Compression is good on all cylinders.
Performed a leak down test and found cylinder 4 was leaking air into the cooling system. Just replaced the head gasket and symptoms are still exactly the same. I didn’t take the head to a machine shop just did it quickly at home but I couldn’t see any cracks in the head.
Am I missing something? Seems like cracked head or bad head gasket are the only possibilities. I’m about to just buy some head gasket sealer snake oil from the parts store I’m out of ideas haha

 

[Schurkey]

Cracked head...cracked block, or failed head gasket possibly due to warped or rough-surface-finish parts.

Most folks will say that Vortec small-block heads are known for cracking.

If you're using the kind of sealer that has waterglass (Sodium Silicate) as a main ingredient, you'll likely have to flush out all the anti-freeze and replace with pure water, or the crack-sealer won't work.

 

[Erik the Awful]

I didn’t take the head to a machine shop just did it quickly at home but I couldn’t see any cracks in the head.
Am I missing something? Seems like cracked head or bad head gasket are the only possibilities.

I took a trio of Vortec heads to the machine shop and got one back. The cracks can be very hard to spot. The other possibility is a cracked block, but that's typically on blocks that have been overheated to hell and back. The heads crack if you ever look at them funny while they're a little too hot.