A/C Conversion help needed

[notsolo]

Been working on A/C 134A Conversion, Serpentine belt setup with R4 compressor (6oz ester oil added), Replaced Evaporator with 1989 model,- flushed out and added new orifice valve, Cross flow Condenser 1995 model (also flushed out) also had orifice valve, left it out... A new Accumulator.... System Charges up fine but high pressure runs up after a couple minutes and throws the belt.... Would putting the orifice valve at the condenser make the difference? it would be flowing across it in the opposite direction...Any help would be appreciated ....Thanks. Ed.