My 351 sputters when the engine gets warm. Actually, more than sputters, it cuts out and sometimes will barely run, a couple times it has died on me. It does it almost always after about 15 minutes of hwy travel. It starts in the higher RPM band and works its way down to where it cuts out at idle at times. When I first start it it runs fine. It would do it intermitently before, but the other day I put a piece of cardboard over the radiator so the water temp would get warm and I could actually have heat in the cab (I think the thermostat must be stuck open). Ever since the engine ran warmer, this problem has been much worse. Tonight it started acting up again, I pulled out the cardboard and of course no heat, but the engine stopped cutting out. Now water temp is around 160 degrees or less on the hyw.

Heres what Ive checked so far:

set timing to 10 degrees advanced (according to specs)
fuel pressure remains at 39-40psi at all times
no EEC codes

Distributor, electronic control module, coil, wires and spark plugs are all 6 months old or less.

New fuel filter, pressure regulator and midship fuel pump, all basically irrelevent to this because fuel pressure is always within specs.

I pulled the spout wire while it was acting up to make sure the computer wasnt throwing poor timing times, the probelm remained.

The only thing I havent replaced yet is the injectors, Im not sure if they could cause this problem or not. To be honest I dont know if the problem is in the spark or in the fuel, I just dont know how to tell.

Any body have any other bright ideas on where else to look?