For piston engines make every effort to run up into wind. That applies to war bird liquid cooled RR Merlins as well as Cessna or Warriors. The engines are usually tightly cowled and there are baffles to direct prop wash and cooling air over all cylinders. That includes rear cylinders and the back parts of the engine where there are ancillaries.
It is all very well to be the nice guy and please others by turning at 45 degrees from into wind so they are not affected by prop slipstream during your run up, but in the end it is your responsibility to undertake a safe flight - and that starts on the ground with good run up practices.
If another aircraft chooses to get that close behind you as to be directly affected by your prop slipstream during run up, then that is his problem - not yours. Having said that, good airmanship dictates you should check all clear behind you before you do the run-up.