Overheating/Hesitation at full throttle

[zachattack_5491]

1990 240sx. DOHC swap.

Ok, so the other day, I filled up my radiator with 50%antifreeze50%water instead of 90%water because it's turning winter where I live. Today as I was driving to school my temp gauge went up a lot higher than normal. I drove home a few minutes ago and it went ALL the way up to the H. So I got home and felt the top of my radiator cap and it was about 40 degrees, which is how cold it is outside right now. The top radiator hose also wasn't very hot either. There is coolant in the radiator so I don't know what the problem could be. ALSO, when i hit full throttle between 2000-4500 rmps it starts bucking like a **** bronco. Kind of like it's starving for air or something. I have no idea what could be wrong. One thing I've noticed lately is my radiator cap doesn't really fit as tight as it should (what can you expect from an ebay radiator) and it leaks a little bit of fluid when it gets really hot/pressurized. AND, I took off my valve cover the other day to get off a severely stuck spark plug wire and as I was torquing the bolts back on in order one of the bolts just kept turning and turning with barely any resistance... so not wanting to strip the bolt or hole any further, I just stopped and moved on. This lack of judgment was also probably due to it being 4:30am on a school night. How bad could that effect things?

This is quite possibly the first cold weather my baby has seen, I think it's been in Phoenix, AZ (2 seasons, summer and spring) for it's whole life up untill I bought it this summer. It's in Gallup, NM now and it's been getting down to about 15 degrees the passed couple days. So... any ideas on the problem would be appreciated.

[zachattack_5491]

Anyone?

[Cone Junky]

Since it was working fine before you changed the coolant, I would guess you just have some air in the system. The driveability problem is probably also related due to extreme head temps causing detonation.