Blowing head gaskets on 1959 Pan

[kickerdel]

Help !!

I am blowing front and back head gaskets always next to exhaust valve. Timing is correct, mixture is correct. Everything looks fine, but I cant go more than half a mile before the gasket blows ! what is going on ?!?
I am running plus 40 pistons, S&S carb, stock lifters, stock pipes at the moment I am running James gaskets, all surfaces are flat and torqued to spec.
If you have any ideas or suggestions please get in touch as I am about to loose all of my hair!

Many thanks

Del

[VintageTwin]

If the heads haven't been milled and if you're sure that the threaded inserts in the head are flat, and not pulled out from somebody re-torqueing the heads while the top motor mount is still connected to the frame then I dunno...wait a minute...have you set the heads on the cylinders without the head gaskets and checked to see that there is no more than 0.010" "rock" gap clearance? If the clearance is more than 0.10", the fire ring on the cylinder must be reduced by draw filing. The fire ring would be topping out on the inside of the head(s). Tighten criss-cross to 65 ft. lbs. Re-torqueing the heads was never an OEM requirement, but if you ever re-torque the heads, make sure that the heads are not held secure from actually moving downward because the top motor mount is still connected (under the gas tanks), and the exhaust headers are removed for the procedure.

[Cotten]

Assuming the heads are flat, then the next concern is heat. Heat is what blows them, particularly under the exhaust port.
The most common cause of elevated temperatures is an intake leak.

[kickerdel]

Thanks for your replies.Im on the case,(again).
Cheers
Del