So here is my wonderful issue that i now have in front of me. (note my sarcasm)

1980 Z28 Camaro with a 383 stroker. The motor has aluminum heads and intake; all edelbrock performer rpm.
Was built 2 years ago, and a overheated it 2-3 times in the very beginning as we were still dialing it in and i changed to a different radiator. Maybe once i had it his 250 degrees, but that would have been the hottest it ever got.
So every summer i have had the same issues. I would add coolant in the beginning of the summer and after a week or two it would start to run hot again and be low on coolant. I'd top it off and it would be fine again for a little bit.

I changed the plugs last year and noticed the oil around the number 8 cylinder, but thought it was only coming from the valve cover.

Any ways, i did a pressure test on the left side last night, as i was seeing white smoke puffing from the tail pipe on that side. All cylinders have great pressure (190 psi and 13.5/1 compression). However, number 8 cylinder has oil and coolant coming from it. I thought it was only oil at first, and it was dripping down from the valve cover, but it's not. the spark plug was all gummed up and looked to be fouled. Upon closer inspection i found it was coolant and oil. I put the pressure tester on the cylinder without the gauge and cracked it a good 6-7 times. I put a bag over the hose and there was a pretty good amount of brownish liquid. not milky really, as it was more brown and watery. It reeked of coolant.

Car has been a bit sluggish as of late and does seem to not be as quick and responsive (in my opinion).

So my thoughts are either one of the following:
blown head gasket
bad manifold gasket
cracked head or block
cracked cylinder wall
cracked manifold

i am about 95% sure that there is no coolant in the oil. its clean on the dip stick, and i didn't have anything when i did the oil change last year. remember, i have had this issue it seams for at least a year to a year and a half.

Could it be a cracked cylinder wall? I am thinking no, because i have good compression... My thought it either a manifold issue or a head gasket. both of with are fine with me, as it doesn't mean the block is bad.

Any thoughts anyone has is greatly appreciated.
Pictures of the spark plug and head are attached

 

Instead of a compression test, do a leakdown test, which can help tell you where you may be losing pressure. Turn the engine over till both the valves in that cylinder are closed. This video shows the procedure.

 

I plan on doing a leak down test tonight actually. I'm assuming that it will not hold pressure, if there is coolant in the cylinder. What would it be telling me if it hold or loses pressure?

 

If it holds well, that would mean you're not losing it past the rings, cylinder wall, or valves. If it's a bad head gasket going into a water jacket, you'd be seeing air bubbles in the radiator.

 

So if it holds well, then its probably a manifold gasket, not a cracked block or head or something like that.

If it doesn't hold, then I'm looking at pulling the manifold and head off...

sound right?

 

Since you're mysteriously losing coolant, I'd say you're at the very least looking at yanking off the intake manifold, regardless of the leakdown results.

 

So I removed the heads last night and found that it was a blown head gasket. much better then some alternatives. I am replacing the gaskets with FelPro as i am not a fan of the ones from Edelbrock, and they are just too damn expensive.
We turned the motor over without anything in the cylinder and antifreeze just came pouring out on each turn.
at least i know the issue and its on the way to being fixed. can't wait.

 

Fel-Pro "blue" gaskets is the only way to go!

 

You got the head checked? Cracks and flatness?

 

We checked the heads; they are flat and uncracked. The leak was seriously about 2 hairs width side and went from the closest coolant jacket by #8 cylinder.
rebuild everything over the weekend, and fixed all my tiny oil leaks in the process. (stupid manifold was leaking oil in the back)
Car runs great and nice and cool again. Pretty happy that i could do both heads and all this in about 2.5 days and have it back on the road and gulping 93 octane. :-)