Exshaust Gases in coolant system.

[Bob Hinz]

Have a 454 engine that seems to be building up a lot of pressure in the coolant system. took the heads off and had them checked and still have that same problem. Doesn't appear to be over heating as far as I can tell. Put on a new Termostat, water pump, hoses just for GP's. I was told that the block was bad and I was getting exshaust gases in the coolant system, but I have a hard time with that. The oil is clean and when I had the heads off, there was no evidence of coolant getting in to the oil. Using a 13 psi Radiator cap, maybe need a larger one? Help!!