1/4 mile times posted

[Thumper]

I hope we both do. I just want to be .000000001 faster:twak:

[Pyro]

Jersey,

I think you need to run a T-stat. Below is a write up on the need for a T-stat. I didn't write it, just a copy and paste job for another car forum.

 

The issue with running without a thermostat is two-fold. The first part is that the thermostat provides drag on the water flow. This drag increases the backpressure the water pump and all of the enginesees. This additional pressure, over and above the nominal 15 psistatic pressure the radiator cap sets, raises the boiling point of the coolant. The reason this is important is that it suppresses localized film boiling at hot spots such as around the exhaust port. The transition from nucleatic boiling (bubbles of steam originating from irregularities on the surface) to film boiling (where the hot surface is coated with a film of steam) is called Departure from Nucleatic Boiling or DNB. DNB is very bad, for steam is a very good insulator compared to water. Once DNB occurs, the area under the steam gets hotter because the steam doesn't remove very much heat, adjacent metal which is still wetted heats from conduction. DNB happens there. The process spreads until substantially all the coolant-wetted surfaces are insulated by a film of steam. The engine overheats. In addition, the buildup in steam pressure forces the radiator cap open, bleeding coolant, therefore making the situation worse.

 

The second issue is that of water pump cavitation and surge. If the pump is operated at high RPM with insufficient head pressure (provided by the frictional losses in the coolant passages and the thermostat), there is a great likelihood that the pump will either cavitate (localized boiling and/or degassing on the impeller) or surge (an unstable flow regime). Either phenomena is destructive. Cavitation's collapsing bubbles act like little sand blaster, eroding away impeller material. Surge can do the same thing and in addition, can vibration stress the impeller enough to break it. Many times what looks like corrosion damage to the impeller, especially when the housing is damage-free, is actually cavitation damage.

 

The myth of velocity originated among those unschooled in physics or thermodynamics, I suppose, because a common racer "solution" is to press a fixed restriction into the thermostat housing neck when no thermostat is desired. The conventional (but wrong) wisdom is that the restriction "slows the water" as stated by the previous poster. In reality, all it does is provide some more dynamic pressure in the block by restricting the flow. The exact same result could be accomplished (assuming the water pump doesn't surge or cavitate) with a higher static pressure (cap pressure), assuming the system could withstand it.