My goodness, a year and no updates...oh how time flies. Some updates.
It's summer and temps are hot here in KS. With rising air temps come the rising needle on the coolant temp guage and since the 331 rebuild mine has too. At the tail end of the OEM and original 302 I had replaced the radiator with a Tom's 3-core aluminum, Tom's steel fan shroud, aa 17" Derale fixed-blade mechanical fan, and a FlowKooler pump and had control of the hearing issue for all intents and purposes.
Rebuild a carb'ed 5.0 Roller and pump it up to 331 and the above radiator setup was fine for start and idle, keeping things at or around 170-180 in traffic to the first grocery getting spot. As soon as I let it heat soak for a few minutes and hopped back in it would come down to around 200 at idle and then once I was on the road at 40-50 MPH it would swing back to 180-190 but stay put. Not alarming but if I then sat at a light it would creep up to 200+. If I sat long enough in traffic or at a light it would stay come down to 190 or so when moving but then creep up at the next light to 210-220+...not heading in the right direction. The most frustrating part is I was getting some form of vapor lock and boiling fuel - we all know the typical crap with our beloved Early Broncos. I want to trail and crawl this thing with my girls and a broke down rig does not a fun weekend make with the wife. So no trail riding yet...
We just swapped out the shroud to a Ron Davis aliminum "full circle" shroud and the fan from the 17" to an 18" and heat soaked cycled the crap out of it in 100+ kansas heat. When I got it back to the house I let it heat soak again and restarted it and parked it in the sun on the west side of the house at idle for 15 minutes. When I got back into it to check and put it in the garage the temp guage was between 170-175!!! I'm not about to say it's fixed yet but I was very pleased to see the guage sitting where it was...right on the thermostat. And the ambient air temp at 6:00 pm was still WELL into the 90's.
Driving to a car show tomorrow and back on its own power. Should be a good test as well - some city driving, some highway driving, and finishing with some more city driving. We shall see...