Sounds to me like you have a bad convertor. If its an impco j2 converter they did not like being frozen off more than twice normally. There is a small steel tab in there that would bend and it would cause high fuel pressure. Pull the primary test port plug (1/4 inch plug with 7/16 head) and check the pressure. It should be about 1.5 psi. anything over 3 psi will give you problems. If you do replace the convertor I would recommend the impco cobra. Its a bit tougher. Hope this helps