The stock impeller is sized to provide enough flow to cool the engine on a hot day at idle. We used the Racing Beat pulley set. Smaller crank pulley and a just a bit bigger pump pulley. This is good up to 10,000 RPM.

I doubt that any modifications would be required if you only need 7,500 RPM. The restricter increases the water pressure in the block and helps retard nucleate boiling around the spark plugs. When you use ice cold heat range plugs (and you should) a bit more plug heat goes into the housing around the plugs. Notice on junk housings that have had very hard use with street plugs, that there are radial crack running from one or both plug holes into the chrome.

My mixture was distilled water. Ten percent Glycol. one teaspoon full of Dawn dish washing detergent. Or, RedLine's WaterWetter coolant helper. Both work. One is cheap. I also used a swirl pot (required by Cosworth

for all of their installations.) The rotary loves to hide air in the engine. Then when the RPMs come up the air wanders about looking for the worst possible spot to stop and insulate some critical location from the coolant.

Air comes to the swirl pot and pops to the top where it is fed to the bottom of a make up bottle. So, as the temperature changes and the volume decreases, only raw coolant is pulled back into the system. Even with a swirl pot it takes two 20 minute sessions to get all of the air out of the system. The make up bottle was the stock piece from any 70s RX-2,RX-3 or RX-7. It was not my idea but it works great. The thermostat is on top of the make up bottle. Use the highest pressure (Stant Lever cap) you can fit to the bottle). The higher the pressure the hotter the engine can get without boiling the coolant. Not a big deal until you need just another 100 yards to make flat ground, or a road, or a runway.

Fire pumps on large ships are called main feed pumps. These huge pumps will not start up unless a specific inlet pressure is reached. In front of the main feed pump you will find two or four smaller booster pumps. The booster pumps deliver the high pressure water to the inlet of the main feed pump. Without the boosters, the main feed would start up and just boil water at the inlet. Part of the impeller would have 50 pounds of water and some of the impeller might have none at all. This imbalance is not felt when a tiny car impeller is used. When the impeller is 4 feet in diameter everyone on the ship knows there is a major problem.

Gained at great expense from 35 years of racing.

Lynn E. Hanover