Hi Lynn I really appreciate your input and would appreciate seeing a picture of your cooling circuit. I should have mentioned, I have temp senders on the in and out of both oil and water, In the test yesterday after 20 minutes of running the oil cooler (Rx7 turbo - not sure which model) drops the temps by about 12F while the water Rad is only about 6F. I’ve seen this as high as 18F oil and 9F water previously. Apart from the cooling system, what else can cause overheating? If I pressurise the system it holds that pressure for some time for over 30 mins. Cheers Steve I > On 29 Dec 2017, at 1:32 am, Subscriber Lehanover@aol.com <flyrotary@lancaironline.net> wrote: > > I started racing rotary powered cars in 1980. An RX-2 with a junk yard engine. Had to pour motor oil and hot coffee into it in order to start it. No compression. People gathered around just to watch me do it. Ran well, never a reliability problem. No overheating problems. Oil cooler was an air conditioning core from a large GM car. Cheap and available. > > I copied the cooling system from the stock RX-2. It had a coolant recovery tank made of plastic. The pressure cap was on this tank. The radiator cap was just to seal the system. Those engines had the giant monkey motion thermostat that closed a hole in the water pump body after a quick warm up.( Pollution control). Stock radiator. Bigger oil cooler. No problems. > > Then I started building bridgeported engines. Big problems. I installed a big aluminum radiator. A double pass top to bottom. This put both inlet and outlet on the same end. Very handy. No problems for a while. Then an occasional overheat after an engine change. I could not get all of the air out of the engine after a rebuild. I lifted an idea from the Cosworth installation manual and installed a swirl pot. The top of the swirl pot plumbed to the bottom of the stock RX-2 recovery tank. So as the engine warms up any air removed by the swirl pot enters the bottom of the recovery bottle. The bottle is kept half full of coolant, so the air pops to the top of the bottle. On cooldown or off throttle situations only coolant can return to the engine. After several sessions of refilling the bottle to one half full, the engine has removed all of the air and full RPM shifting is available. For us that was shifting at 9,600 RPM. Coolant temps 180. Oil 160. At low RPM the air will not come out of its hiding places. My idle was 2,200 RPM. Timing is checked at 4,000 RPM. Clear out the bubbles at least at 4,000 RPM. > > On cool days (below 65 dgrees) we would install a thermostat that had two 5/16 holes drilled through the flange. > And tape over half of the radiator. > > Some items are not obvious. > > The best coolant pump location is at the very bottom of the coolant loop. The rotary pump is at the top of the coolant loop. The pump will gleefully stop pumping if a dose of air enters the suction side. Very bad MOJO. The center irons on 12-A engines at first had a temp sender hole. Great place to let air out of the coolant before start up. Then the hole was filled in but the machined flat was still there as well as two tapped holes. I drilled and tapped for 1/4 pipe and installed a radiator bleed fitting. Got out lots of air before even running the engine. > > The recovery bottle need not be mounted high in the circuit. That bottle in the racer is mounted on the passenger floor. Also the top of the swirl pot need not be mounted high in the coolant circuit. Does not matter. > > I found a Stant pressure cap for the RX-2 bottle rated at 28 pounds. I installed a Shrader valve in the swirl pot and pressurized the whole system to 28 pounds before start up. This also tests the pressure cap. > > My coolant is 10% prestone antifreeze. 1 bottle of RedLIine Water Wetter, or 1/2 teaspoon of Dawn dishwashing soap. The rest is distilled water. And 28 pounds of pressure. > > The racer is gone now but the last iteration of the coolant system is as above. The oil cooling had to be improved as HP went up. (Store bought engines). Daryl Drummond 250 HP 12-As. So the last oil system was a full dry sump with one 44 row setrab in the pressure loop. And two 44 row setrabs in the scavenge loop. We ran 100 pounds of oil pressure with 40 weight RedLine racing synthetic. No oil related failures > since 1980. The modern "Square" Peterson pumps tend to split open the pressure section. I changed to the older round body Peterson, no problems. > > Lynn E. Hanover > > I will draw the coolant loop if you like. It was published many times but died several computers ago. -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html