wich is better for a radiator cap
 

A 24 Pound Medium Radiator Cap

or

A 15 Pound Medium Radiator Cap

take in mind , I will autocross occasionally and do daily driving
Bruce

I would never run the cooling system at 24psi. Just asking for trouble... Run the 14 or run the stock one.. just use a bottle of water wetter and distilled water only and you'll be fine.... I hardly see over 192F with the turbo on full boost runs... you should be fine N/A

the 24 is "better" for cooling while your moving, but if you turn the engine off after a hot run without a cool-down, my guess is that the coolant will boil over...anybody agree? If your on the street I would stick with the standard cap...

Dont be a sore looser Jesse. I would also recommend the 14 because i will be a daily driver occasionally.

Do you know if the 300ZX TT rad. cap will fit the FS-DE rad.?

The reason for higher pressure in the cooling system is because coolant boils at a higher temperature the higher the pressure is. At 24 PSI the boiling point is over 250 degrees. The problem becomes whether or not the radiator can take continued high pressure. The radiators in these cars are aluminum with plastic ends clamped on and have a gasket between the tanks and the radiator. Continued high pressure will definately shorten the life of the radiator. Competition radiators that are completely welded solve that problem

Also, the stock hose clamps are of the spring clamp variety. Spring pressure in the metal holds them on. These are all potential leak points at higher pressures. The way to get rid of the problem before it crops up is to change all the radiator hose and heater hose clamps to a more positive clamping variety like a screw type. Make sure not to forget any clamps. With a stronger radiator and good clamps there is no reason this shouldn't last a long time.

I still think that a larger radiator would be a good idea if the power is really bumped up though.