Chevrolet: Replacement engine running hot, radiator pressure tester, gmc sprint

Question
QUESTION: I have a 1973 GMC Sprint (El Camino).  The engine was burning a lot of oil, the cam was out etc. so I decided to replace it.  I bought a stock GM Goodwrench 350 engine from Summit Racing.  I just put it in and it runs great.  However, it appears to be runing to hot.  I have an SW guage set that I added and the temperature sensor is in the passenger side head between cylinder 6 and 8.  It shows the engine is running around 200-220 degrees with the A/C unit running (180 degree thermostat).  When I replaced the engine, I had the radiator rodded out and checked.  I replaced the thermostat with a 160 degree unit with the same results.  The flow through the radiator appears to be good looking through the radiator neck (the water pump is only 6 months old).  I replaced the fan clutch (since it showed signs of leakage), still the same results.  I took the temp sensor out and put it in a pot of boiling water and compared its reading to a digital thermometer.  They were withing 5 degrees or so.

Anyway, I'm at a loss as to what is the matter if anything!  I know the old engine ran around the 180-190 range.  I thought it should run around the temperature of the thermostat.  Any ideas?

ANSWER: Ken
Hi I would put a water temp. radiator pressure tester on it and see if there are any leaks if it will not hold psi than you have a leak, how is the rad.cap, do the belts slip, I would remove the therm. all together. are the hoses good, is the top hose getting sucked closed when running. check all of those ok.

---------- FOLLOW-UP ----------

QUESTION: I just bought a radiator cap with a thermometer in it from Summit at lunch to do a comparison (they have a retail store less than a mile from where I work).  The previous cap was new.  There are no leaks and it is holding pressure.  This is a side draft radiator so the suction comes through the bottom radiator hose.  It is new and has the spring/coiled wire in it so it is not collapsing.  The guy at Summit said 200-210 is about normal.  Hmmmmm.  I also bought some wetting agent to add to the coolant to see if that helps.  It just bothers me that the old engine wasn't running this hot.

Answer
Ken
Hi -well I had a 396 and a 454 and they both had a lot of work and goodies on them, well the 454 ran at  apx 165/70 max and the 396 with a larger cam ran at 180 at all times and that was with no thermostat in it  at all.Do you have a shroud on it or was it taken off and is the fan close enough to the radiator.