overheating problems

[dropped_71chevy]

My truck got hotter than usual (not really overheated just above 180 degrees, which is normal) about a week ago and I decided that my heater core was the culprit.

I replaced the heater core and was on my way. Two days ago it overheats again. I fill it with about a gallon of 50/50 mix. Today it overheats again. I fill it and it goes back to normal of course.

What would cause this to happen? I pulled the dipstick and tried to smell and see if there was any antifreeze in the oil. I couldn't tell. Tomorrow I will do a sniff test with some plain oil and some of my engine oil to see if there is a difference. The only thing about that is that my oil level hasn't gone up at all.

When it overheats there are two little puddles on either side of my intake manifold where it meets with the head.

Also, my oil pressure is high when it's cold and then when it is at operating temperature it drops down to exactly half on the stock gauge. It goes up as I accelerate.

Would my exhaust smell funny if I was burning antifreeze?

I recently built this engine. We dyno'd it and it held together fine for about 3 weeks until it got hot that first time.

Any help is greatly appreciated. Sorry about the long post.

Thanks

Tim