I am having similar issues. My intention is not to hijack this thread, but to see if we can get these issues straightened out together. I also have a 340, however mine is stroked to 416 cubic inches, bored .030 over, with edelbrock heads march pulleys and also a 180 hi flow thermostat, and I also have the six pack hood on my duster. My timing is set at 38* total, which is where the dyno said she liked it best. So some pretty good similarities here. However, I am running a stock waterpump, but with an aluminum circle track radiator and a derale electric fan and aluminum shroud, flows around 2400 cfm I believe.
Now, my car will take a while to warm up, maybe drive for 5 miles before it hits 180 and the fan and thermostat come in. Now mind you I have 3.91 gears so that five miles is at 3000 rpm, so I dont think that is too bad. When I get into town and I am running 180*, I will run there all day long as long as I'm idling or driving though town slow i.e. 35 mph. But, once I get out on the open road again, the temp gauge will climb, eventually to 210, 215*, maybe taking 15-20 miles to get there. Now, once it is at that temperature, if I slow back down, to say 35 mph again, then it will take FOREVER for the temperature to come back down to 195 or so. Its almost like once I get it warm, it doesnt wanna come back down without a fight. I dont think 210 or 215 is gonna hurt my engine, it wont, but its on the warm side for my tastes. Id like to get it down around 195 operating temperature.
These are a couple of things that I know are hurting me
1. Stock water pump is obviously a weak point. My engine dynoed at 465 hp on pump gas, so I increased the hp over stock by around 60%, however I did not increase my coolant flow at all.
2. I have my B&M transmission cooler mounted on the front of my radiator which is impeding flow going down the road, but unfortunately on the small duster there isnt much room to mount it anywhere else where it will be in front of the fan, and with my 3500 stall converter, my 727 stays below 170* all the time, so Id like to keep it there.
3. I contacted Mezier about their electric water pumps and their engineer said that my 6 pack hood is hurting my temps bad, because all the air rammed into that scoop is filling the engine bay and fighting the air trying to come across the radiator. He said to seal the hood to the engine. I am not sure about these claims, but it is easy enough to get some foam and block off the scoop just to see if it lowers my temps.
Since my car is only on the edge of running hot, I am going to drain the coolant and fill it back up with only distilled water and water wetter since it is summer, and obviously it will be drained before it gets cold here in ohio. I believe this should drop me 10-15 degrees. I will let you know my results.
Finally, I also considered that my head gasket may be leaking, however if it is its a very small leak, because I dont really lose any coolant and my oil was nice, free of sheen or anything when I drained it (engines got 700 miles). And quite frankly the engine runs too damn good to be losing any significant compression. So to be on the safe side I am going to do a leak down test on my engine to rule head gasket out.
Skeven33, I hope that this information has maybe sparked an idea or two for you so that you can drive and enjoy your car. Now, maybe if some other members chime in with their experience and help us out we can both get our cars under 200 degrees on the hot days
