I have a transplanted 1986 chevy 305 with tpi in my Jeep. I eliminated the stock CJ heater etc and am now overheating . I connected the heater hoses as I thought was correct to reroute the coolant. the two front tubes (at the front of the intake are connected together and the passenger side from the air intake is plugged.). I also recently replaced my gauges with new autometer gauges. Two minutes after starting it, it jumps to 250 degrees. I have a new four core radiator and a push pull fan along with the standard mechanical fan. The thermostat is less than one year old. Please help!

What has been changed or replaced on the motor since it was running in the previous vehicle? Is timing properly set? Is your water pump the correct rotation? Is your lower radiator suction hose collapsing when running?

The block has been in the Jeep for about five years now. The only changes I have made have been a new radiator, different gauges and today I switched to a 160 degree thermostate. I will hit 250 degrees in under five minutes.

Sounds like air pockets in the coolant, giving an incorrect reading. Did you fill the rad all at once or slowly with it running?

Sounds like air pockets in the coolant, giving an incorrect reading. Did you fill the rad all at once or slowly with it running?
X2 sounds like it airbound.

Thank you everyone for your advise! I agree that it's air in the system too. I am going to have the block flushed and refilled. It's a 22 year old block and I'm sure I've got some crude in the water jacket etc.