Exh manifolds in an Early A...

I have used early A 273 manifolds on a 318 before with leaks. Both heads and manifolds were checked for straightness. No idea “why” they leaked. I switched from the 318 small port gaskets from FelPro (metal clad) to a 3/32” cut gasket white in color made for the 273 port thru Jegs. I do t remember the brand but they were an asbestos like product (high temp) and that solved the problem. I even used the proper mounting hardware (con washers, studs and proper nuts) any how Jegs sells the proper port sized gaskets. Not a fan of the Felpros anymore. Really poor quality.