250 6 cylinder exhaust manifold leak

[Conroe trucker]

Hello Guys,

I have a rebuilt 250 6 cylinder engine and am having hell getting the exhaust manifold to seal after the first cylinder at the bottom.

I am also curious if the exhaust preheat valve could be sticking and causing additional back preasure.
It is not sticking, but what if I wired it open?
Picture on the left is at rest while warm.
Picture at the right is under some tension to old in that position.
Can anyone tell me which off these is the open position?

I have a really quiet muffler on it, so I expect I have some back preasure anyway.

I put the second gasket on and it did not seal at all, looking for ideas.

I thought I read that you must put the intake and exhaust on together but not bolted up, tighten everything, then tighten the preheat cavity.

Also looking for a tuning schematic for the 1BBL carbs if you might know where to find one.

Mike
CUSTOMAL@FLASH.NET