no it isn’t cobra.

I’ve back flushed the block through flow was ok

Open up the Trans cooler. Has a small cover on the end 9/16 bolt. Its the first cooler after the pump. They can get clogged there with sea grass. Happens a lot. Also you really should be running 25-35 psi of water pressure in a 1075. I usually change the thermostat to140 deg on all the rebuilds.

As both headers were not the same I went as far as swapping the motors to see if it was in the headers/tails.

i can confirm it is in one of them as the side (different engine) is now overheating

Does anyone know how I can unclog the tailpipe
or header?

thanks

Take the headers off and back flush them to start

fill the pipes with muriatic acid for a few minutes then flush out with water.don't be surprised if you have pin hole leaks.

I do think you're onto something, but your water pressure around 20PSI seems pretty low. I'm pretty sure on the 1075's, the water pressure sender is located in the port side of the bellhousing, which is before it enters the block. So, in that case, I would assume any blockage in the block or headers would be causing high water pressure, not low water pressure.

Why do you switch to the 140? Are the 1075 thermostats just standard BBC 140 stats like they sell at Hardin?

Yes high flow 140 deg thermostat.

So just and update on this…

I have replaced the tails on the engine as I found a leak in them. The engine is still overheating.

i have taken off the headers as that’s all that’s left. I have found one is leaking but it is not a major leak.

i do not know if that would cause my issue

I don’t think leaky headers would cause an overheat…