fouling number 4 and 7 with gas

what kind of plugs are you running/ i've noticed that my car was doing the same thing and after i changed the plugs it worked fine, but after about 5 runs i was back to the same problem... cheap plugs
 
what kind of plugs are you running/ i've noticed that my car was doing the same thing and after i changed the plugs it worked fine, but after about 5 runs i was back to the same problem... cheap plugs
 
anyone have any ideas....it did it with the stock motor and it did it with the next motor (we think) before it dropped a valve. we would just hate to get this motor together and have the same problem. we switched the injector harness already on the last motor. havent pulled codes yet since the car is still apart, but we will once its running
 
well never know until we get it back together. well try a different distributor and if that doesnt work we will get a set of noid lights and check the injector harness. we can also check all the injectors