If you add flow to the back of the heads at sufficient pressure to overcome the flow from the block then you cool the heads at the expense of flow through the block. which will get hotter.
If you could figure out a way to remove the hot water and replace it with cooler water then it would help.
The Constitution needs to be re-read, not re-written!
If you can't handle Dr. Seuss, how will you handle real life?
Current oil burners: MB GLK250 BlueTEC, John Deere X758
New ride: MB GLS450 - most stately
Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510