Hydroboost issues....to sensitive

[Hydratech®]

Note that most factory hydroboost spec pumps "out there" are truck model pumps, unless you specifically ordered in a passenger car spec pump from say an early '80's GM diesel car (though usually only can find low end remans, as the days of new old stock on these are gone). The truck spec pumps flow a LOT - typically around 3.5 to 3.7 GPM, while the passenger car spec pumps flowed in the area of 2.5 - 2.7 GPM - MUCH less. That high flow is great for short slalom racing where you want the fastest possible steering response, but highly destructive for extended high RPM blasts on a road course. Swapping out the PS pump output fitting to one with a smaller central jet / orifice size will bring the flow rates down, cooling the system down considerably. Adding a cooler is always a good idea, as short of freezing temperatures, PS systems prefer to run on the cooler side. Too cold, and you won't burn off any moisture in the PS fluid, and it can take MUCH longer to degass the fluid (air in suspension in the fluid). Short of using an A/C condenser (!) as a PS cooler, you will always count on everything under hood to run at a similar ambient temp, so the PS system will always come up to basic temp. Steering gears solidly bolted to the frame actually reject some heat throughout that area of the frame, providing a measure of some inherent cooling - not much, but measurable. Rack conversions can actually lower PS system temps a bit more, as the racks are typically in a good air stream, made of aluminum which conducts heat well, and have a pretty good sized overall surface area to radiate heat (providing some cooling effect). The auxiliary cooler is a way of also adding fluid capacity to a PS system, which is always a bonus. What a lot don't realize is that the cooler is pretty much along for the ride when just rolling down the road. BUT, as soon as system temps start climbing in a road race scenario for instance, system temps start rising quickly. This starts "passively activating the cooler", as the higher the temps climb, the more heat the cooler starts transferring. If the ambient air temps are 90 degrees or so, and the PS system is at a general under hood temp of say 180, the cooler will be actively radiating heat off in the airflow. The hotter the system gets, the more heat the cooler will radiate as the temperature differential increases. 90 degree day, 180 system temps, basic heat radiates. The same 90 degree day with a PS system temp approaching 200 degrees, the temp differential increases where the cooler then starts radiating a larger amount of heat. It's an interesting fact that these cooling dynamics exist. Again, reduce your pump flow and go for a trans cooler - not a PS cooler...

I don't want to open a can of worms with this statement (I can hear it already), but I have "modulated" the viscosities of PS fluids in some road race cases over the years by spiking them with a bit of synthetic gear oil. Why? If you have an inherently hot running road race car that doesn't have adequate PS system cooling, the PS fluid starts getting thinner and thinner and thinner as the temps climb - almost water thin when super hot, next step leading to a system foam out. Spiking the system with 4 to 8 ounces +/- of the synthetic gear oil provides extreme pressure additives, more viscosity, and a large dose of anti-foaming agents. I do not recommend this for basic street / strip use, reserving this trick only for cases that are acting up at the track. After the road race is completed, we advise the system be drained, an appropriately sized cooler (typically 8" X 4" thereabouts) be installed, with a good clean fill of a quality aftermarket synthetic PS fluid. This is just a quick emergency band aid for a temperamental road race PS system to get it through to the finish line.

6400 RPM isn't that high. Factory SVT Cobra 32 valve Mustangs had hydroboost, winding WAY higher than that out on the road courses. What you may have to look at besides everything I mentioned above is your pulley ratio. A general street / strip car would for instance have an average of a 8" crank pulley to a 6" PS pump pulley - an overdriven PS pump speed to provide proper parking lot performance. Dedicated road race cars will run a smaller under drive crank pulley to keep alternators from exploding, water pumps out of cavitation, and PS pump over speed. The NASCAR teams are now running power steering to reduce driver fatigue, but their pulley ratios are specifically set up for the sustained extremely high RPM's - small crank pulley compared to a large PS pump pulley (also much smaller cam ring profiles inside of the PS pumps producing much less CC's per revolution) - not much assist while in the pits. You may want to look into what may be available to downsize your crank pulley. Do please keep in mind that this could cause some negative side effects at idle speeds less than a 1000 - 1200 RPM though - it's a trade off of low speed operations for high speed stability, so don't make a huge change in crank pulley size - 1" smaller can make all the difference (or optionally go the other way with a larger PS pump pulley if possible). I recall when I grenaded an external alternator fan blade at 7800 RPM - it shot shrapnel right through the hood, wheel well, and right out the fender! All of the other pulley speeds were ok, so the installation of a larger alternator pulley solved that, but at the expense of idle speed charging output...