I'm assuming the timing is in the ballpark & the mixture is also (no vac leak). Is that stoplight to stoplight driving? If you take it out on the highway what does the temp do? I'd maybe shoot it with an IR gun to confirm what the temp actually is & my first step would be to toss the stat for a day which wont hurt things. What's the history of the radiator? You mentioned the cap, is it loosing coolant?