Whenever a VR unit is installed on the engine, either as a new installation, or as a result of a re-installation after maintenance or replacement the oil drain hose should be disconnected from where it is connected at the oil pan, and the drive belt for the supercharger should be removed. The engine can then be safely started and run at idle to oil comes out of the drain hose, when this occurs the engine should be switched off, the drain hose reconnected and the drive belt installed. This procedure safely primes the supercharger and minimises dry running after supercharger installation.
Change engine oil and filter every 3000 miles. DO NOT use synthetic/semi-synthetic oils, oils containing detergents, or friction reducing compounds/fluids, or stop leak type products. STP (Supercharger Termination Probable) is particularly good at destroying superchargers. Ford actually strongly recommended that only SAE30 oil should be used, a recommendation that may well be worth following.
The life of the supercharger is heavily dependent upon the quality of the engine oil being fed to the supercharger. Any contaminants or particulates (particularly combustion gases) can score or corrode the bearings and races, and eventually destroy them, so apart from the regular engine oil and filter change it is recommended that additional filtration (i.e. OBERG inline filter or similar) is added to the oil supply fed to the supercharger. Paxton actually produced an oil filter kit (38675) for the later VR58 superchargers this comprised of a bracket (38231) which mounted the oil filter (38242) to the blower case, and a pressure switch (38243) which was used to illuminate a warning lamp when oil pressure dropped something like this could be built fairly easily as its unlikely that many original ones will turn up. An inline oil cooler, either for the engine in general, or specifically for the supercharger oil supply, would also be beneficial as it would allow the supercharger to run cooler.
Paxton optional oil filter kit
Apart from lubrication and cooling of the supercharger in the case of the VR systems the oil is also used to control the blower speed. When the supercharger is in high ratio (manually invoked by control lever) oil pressure is allowed into the piston chamber and acting upon the piston that drives the races into the high ratio position. In order for this to work correctly a minimum engine oil pressure of 20 psi at idle and 40 psi under load is required. If necessary the oil pressure in the engine can be boosted by installing a 5/16 spacer under the oil pump relief valve spring. A low oil pressure is generally indicative of a worn engine, or of problems with the oil system, which should be rectified before using the supercharger. Usage of the supercharger with oil pressures below these minimums will guarantee failure of the supercharger. The actual pressure within the VR supercharger is limited to 35 psi by a pressure relief valve in the control valve. The Paxton VR installation kits generally provided a T fitting which allowed the oil supply line to the supercharger to be installed at the point where the oil pressure sender is located on the engine which is generally the highest pressure point of the engine oil system. The T piece allowed the sender to be retained.
Some of the more adventurous have considered that a VR unit could be provided with a dedicated oil supply with its own reservoir, filter, cooler and pump, although Im not ware of anyone having done so. This would pretty much guarantee that clean oil was being pumped through the supercharger, however the main risk would be that failure of the pump used to provide the pressure in the supply would mean failure of the supercharger. This is a more likely event than the failure of the conventional mechanical oil pump used to provide the engine oil pressure failure of that pump tends to manifest itself as the gradual deterioration of oil pressure over time.
The oil return line from the supercharger to the engine sump should always maintain a continuous downward flow, with no part of the drain hose being below the elbow connecting it to the hose pan. Failure to observe this will result in oil build up in the supercharger and ultimately will lead to oil being blown into the carburetor and potential oil leakage and seal damage in the supercharger. Similarly you should regularly inspect the drain and supply hoses for kinks and restrictions. Any kinks or restrictions in the drain can result in a build up of oil in the blower with subsequent leakage and seal damage. Kinks or restrictions (apart from deliberate restrictions) to the input supply can cause loss of oil supply and subsequent supercharger failure.
Paxton oil connection instructions
It is possible to check the oil level within the supercharger with some of the VR units by removing the drain plug from the side of the supercharger housing and operating the engine at idler rpm. A rise of oil level at idle within the supercharger indicates drainage problems either through kinks or restrictions.
The oil return from the supercharger is possibly an area that could be improved upon to prevent potential problems with the supercharger. To prevent blowback from the sump (due to crankcase pressure) an extra large return line, ideally with some sort of baffle system, should be used to connect the supercharger to the sump. Any build up of oil pressure within the supercharger can cause seal damage or failure, and result in oil being forced into the air being blown into the carburetor.
Indeed, the Ford VR57 Phase I, and some early Phase II, installations originally used a small diameter oil return line which caused problems with more oil getting into the supercharger than was getting out. This was resolved in later Phase II installations via the use of a larger diameter oil return pipe. Also in some Thunderbird installations a restrictor was added to the oil feed to the supercharger to reduce the input pressure, which could be a bit over enthusiastic.
Ford VR57 oil connections
DO NOT drive the supercharger without the discharge duct (connection between the supercharger and carburetor bonnet) being in place, for more than one minute, and never above idle speed. To do so can result in failure of the supercharger. Similarly it is wise that when a flapper valve is used in the induction system correct seating should be regularly checked, as the failure of the flapper valve to seal under boost can result in supercharger failure.
DO NOT Run the engine for more than a few minutes without the supercharger drive belt being place, without plugging the oil pressure feed to the supercharger, otherwise the supercharger will fill up with oil which will eventually be sucked into the carburetor.
When storing or working on a VR supercharger DO NOT allow the supercharger to lay on its side. It should be held in a fixture or stand so that it is in its normal mounting position this prevents oil build up on the seals and possible future leakage problems.
Oil leakage problems, assuming that there is no oil build up within the supercharger due to line blocks or kinks, are generally at the control valve or the input and output shaft seals. Control valve leaks are generally due to poor seating of the control valve cap in its bore in the bearing housing, or a misaligned upper diaphragm spring. Output shaft seal leakage tends to manifest itself as engine smoking or plug fouling although excessive leakage can cause leakage to occur at the control valve as well. This leakage normally occurs as a result of a worn /perished seal, or improper seating of the seal in the seal bore of the scroll housing. Input shaft leakage is generally attributable to worn/perished seals. In the event of oil leakage the oil pressure relief valve should be checked for blockage as over pressurisation within the supercharger causes leakage at the seals as well.