[Bru]

Very strange that this condition would happen to 2 different engines if I read your reply correctly. I was going to suggest that the head or the block was warped. Seems combustion gases are leaking into the cooling jacket. I've seen blocks and heads that were unusable because the cooling passages, especially on the combustion side, were rotted too close to the sealing ring around the cylinders. What type of head gasket are you using? Standard Toyota or aftermarket stacked metal? When I had my block and head shaved they took off 20 thousandths more than Toyota allows which is 10 thousandths total. I used a 0.020" METAL shim gasket on top of the block sprayed with Permatex Copper on the bottom only. Then I used a standard Toyota head gasket on top of that. I've had no trouble after 35,000 miles. One of the hardest things to find nowadays is a head that hasn't been cooked soft or over cut. Several of the exhaust manifold studs on mine had to be replaced using helicoils to renew the threads.