I am looking hard at getting a 390 with a mild build (less than 400 HP) built for the XR7-G and putting the original engine on a stand for now. I don’t want to ruin the correct engine for the car, and I would like to play around with power for a few years before doing a restoration on the car.
My main question right now is about the cooling system. Will the stock radiator that came in the car be enough capacity for this engine if I get it rodded/recored or will I need to go to a bigger radiator? I don’t have a problem doing either since it will be a non-original motor in the car, but if the stock radiator will work, I don’t see any point in buying an aftermarket radiator.
From my years of experience of big blocks in Cougars/Mustangs if you are going with a rebuild/bored engine I would invest in a extra capacity or desert or 4 tube or aluminum radiator. Plus a high flow water pump to keep the water flowing when idling. Must have a fan shroud and a clutch fan is recommended with blades no more then 2 inches back from radiator. Currently there is the discussion about 160 or 180 thermostat?? But get a high flow thermostat that opens wider. Find a NOS/Ford temperature sender for the intake manifold. Like the repro fuel senders the aftermarket/parts store temp senders have the wrong resistance.
I literally just picked up the radiator for my G yesterday. The original VIN stamped head on the G is Feb. '68 and this radiator is 2nd week of Feb. '68 so I assume it is original.
When I took it to them, the radiator shop said it had already been recored and with the wrong size (slightly smaller) core. So they restored the original tanks and brackets and recored it with the proper core for $443.55.
I am now wrestling with having my 1968 water pump rebuilt or going with a higher flow new one like ClawIt mentioned.
Anyone have recommendations on a good, modern high flow water pump for a 390?
OK, I just restored the clutch fan setup and I have a shroud on the car. With the water pump that is on the car (non original), the fan already sits close to the radiator. I may have to go to a different water pump if I am going to install a bigger radiator.
Big Matt, the stock radiator had two row cores and they were spaced to the rear, that is towards the fan. There is an empty area in the front side of the radiator that will get filled when they put in a four row core.
Horsepower equals heat. A 390 with a mild build will still make less horsepower than a 428CJ and they were able to cool those with stock radiators and fans and shrouds.
The stock original 390 radiator is three core in a 390GT with AC for '68. Generally if the core is new and the correct one they will cool anything up to around 400 HP as long as the AC is off.
I would invest in a good copper / brass 4 core radiator for best results.