I have had one heck of a time getting my intake on my '67 250 to keep a seal. I have had the manifolds milled (intake/exhaust together), used Felpro gaskets, and Permatex Copper Spray-A-Gasket. I torqued all of the bolts/nuts to the proper settings and retorqued after one thermal cycle. Everything runs fine, idles great, good smooth power; then after about 100 miles of driving, it begins to miss at idle and generally runs rougher as the RPM increases. I'm on my third go around with the same poor results. I really love the engine when it runs correctly, but I'm at the end of my rope. Any suggestions?
Thanks,
Dan
