engine oil cooler electric pump size for chrysler slant six

I have a 73 Chrysler with a re-powered 225 slant six, balanced, carb & cam improvements. Runs great. Issue is after about 45 mintues at 50% rpm or more the oil temp very slowly creeps tp 260-280.. Water temp is normal, oil pressure is 40psi. I have a remote oil filter & I am considering an oil cooler thermostatically water cooled by an electric water pump. Anyone had any experience adding an oil cooler? Sizing and intake/exhaust fittings or other suggestion?

 

Keep it simple. Install an oil cooler using the engine's coolant system. Adding a pump and thermostat increases the possibility of failures; what isn't there cannot break down.

 

I have a sherwood D60 water pump and I wasn't sure it would have the extra capacity. Unsure of that point raised a concern that I would be reducing the water cooling by making it cool the oil as well. Chrysler did use it on the 318 as well so I may be fine. Plus I am not sure how to tie it in to the system. It cools the engine block and has another loop that cools the intake manifold. If the new system failed I would not interrupt to main cooling system. Chrysler Boat works is long gone to get engineering support.

 

You can use the loop to and from the engine block.
The overall cooling capacity doesn't change because the amount of heat generated stays the same. Instead of removing it only through the water, part of it will be transferred through the oil. The water flow to the oil cooler should be 10-20% of the total amount circulating.
You can control that by using the proper hose size or add a simple ball valve in the circuit which you open a bit at a time until you are satisfied with the oil temp.

 

Adding oil cooler

Thanks CDK - It makes a lot of sense as you said the total cooling capacity is then being split between the water & oil cooling.
I did increase compression slightly, slightly more aggressive cam, and increased carb size - all engineered by a professional rebuilder. I think that may have increased the cooling requirements as it went from 155 hp to 175/180. Biggest difference is a very pleasant surprise of fanatastic fuel effieciency! I did add bennett tabs as well as it would not plane unless 3/4 throttle before! Only way this could be an issue (tie-in existing pump) is if I increased the heat generated by the engine by the repower. With my rebuild I added water pressure & engine oil temp guages. Not having them before means I really did not know what the oil temp range was before. I believe engine oil should stay in the 180-220 range. Over 220 the oil breaks down I'm told. The ball valve is a great idea so the hose size calculations are more forgiving

 

I would build a deeper/bigger sump and or with a baffle/windage trayto keep the oil away from the crank. Nothing to go wrong, no extra parts, free horsepower increase.
I have experience of just removing oil from the sump and it lowers the oil temp, like right to the bottom of the dip stick.
Not many cars can drive at 50% or 100% for 45 minutes so you see the original design is not really up to the job in a boat and all the sumps on usually just from a car whch is designed to go around the chassis/steering etc so far from the best design for the engine in a boat that doesnt have to accelerate and stop or go around corners flat or rolled outboard.

Oil over 200f is no problem
maybe getting to 260+ is a problem I have seen plenty that run at 300f, most users dont realise as they dont have oil temp gauges
Your engine has solid lifters but with hydraulic ones they airate and bleed down, just lower the oil level and its fixed.