This section introduces the VR57 via a history, and will be followed by operation, maintenance and installation sections at a later date. Ford and the VR57 are heavily intertwined, hence the large Ford content in this section. My thanks go to Dan Evans for supplying a substantial part of the material, and for reviewing whatís been written.
Following the introduction of the VS57 supercharger in late 1953 and early 1954, Robert Paxton McCulloch set up the Paxton Products Division of the McCulloch Motors Corporation to handle the sales and marketing of the McCulloch VS57 supercharger, and to research and develop new supercharger applications, improvements and variants. Supercharger manufacture was still under the auspices of the McCulloch Motor Corporation, although that too would pass to the Paxton Products division later on in the decade.
One significant early product that Paxton Products developed was the supercharger used on the Novi cars raced at Indianapolis. These were engine oil cooled conventionally mounted superchargers which were gear driven at a ratio of 5 ľ to 1 and had impellor speeds of up to 40,000 rpm. The supercharged Novi V8 engines were capable of producing up to 650 hp from 180 cubic inches, however power is not everything and they were generally unsuccessful in racing, although this was not attributable to the supercharger. The Novi name, and itís connection with Paxton, still lives on today as Paxton Automotive currently produced high output gear driven Novi superchargers.
The direct oiled Paxton Novi
Another product that Paxton Products designed during 1955, and developed during 1956 was the variable ratio supercharger. This was developed to provide a general purpose supercharger that was more compact, and easier to install than the VS57, and also had greater boost and air flow handling capabilities. The resultant supercharger, which is commonly known as the McCulloch-Paxton VR57 differed from the VS57 superchargers in that instead of the planetary ball drive being a fixed ratio, and the drive pulley being a variable ratio, the planetary ball drive had a variable ratio, and the drive pulley had a fixed ratio. Another more significant difference, which no doubt benefited from Paxtonís involvement with the Novi, was the use of engine oil for lubrication and cooling.
The variable ratio planetary drive was achieved using split inner and outer ball races that varied in separation according to the input shaft speed. At low engine and input shaft speeds the inner ball races are pressed together with springs, forcing the balls between the races to ride higher and forcing the outer ball races apart, giving an impellor ratio of 3.5 to 1. At higher engine speeds, engine oil pressure forces the outer races together via a piston, forcing the balls into a tighter circle and giving a ratio of 5.5 to 1. This ratio varies between 3.5 and 5.5 to 1 against engine speed due to engine oil pressure gradually overcoming the spring pressure against the inner ball races. A supercharger drive pulley ratio of between 1.7 and 2.0 to 1 allowed the supercharger impellor to be driven at ratios of up to 11.0 to 1, which, as for the VS57 units would allow impellor speeds in excess of their rated 32,000 RPM maximum. To limit the impellor to itís maximum, boost output from the supercharger was used to reduce the oil supply to the split races, allowing the planetary drive to drop back into low ratio as engine speed increased. Interestingly the impellor is the only component that is common to both VR and VS superchargers.
As with the VS57 the VR57 could be forced into hi ratio, and in this case this was achieved using a throttle activated valve which diverts the oil supply direct to the piston acting on the outer ball races, thus increasing oil pressure on the outer race. This was also regulated by the increasing boost pressure as the boost output of the supercharger increased.
Phase I VR57 (Ford Motor Co.)
The use of the variable planetary drive arrangement in the VR57 eliminated the need for the variable ratio pulley and tensioned idler arm set up used in the VS57. In the case of the VR57 a conventional supercharger drive pulley could be used in conjunction with an adjustable idler pulley for applying tension to the drive belt. This elimination of the idler arm and variable ratio drive pulley allowed the VR57 to be slimmer in profile than the VS57 unit, although itís diameter was slightly larger, in order to accommodate the larger drive balls and races required to give the variable ratio planetary drive.
This greatly reduced the installation requirements of the supercharger, and allowed for more compact installations, minimizing the need for fan blades and radiator re-positioning . The use of a standard drive pulley on the supercharger input shaft also provided the added bonus that standard ĹĒ drive belts could be used in conjunction with standard crankshaft and idler pulleys, allowing for an easier installation by the home mechanic when bought as an aftermarket kit, and again offering minimized clearance problems.
With the horsepower race heating up in 1955, Ford realized the importance of offering performance equipment for their vehicles. Winning on Sunday meant increased sales on Monday. Superchargers and fuel injection were being considered and researched by Ford, but they were not expected to be available for the 1956 racing season. As a stop gap solution Ford commissioned Buddy Bar in Detroit to make dual four barrel manifolds for them, to be used in conjunction with special Holley carburetors. The Ford engineering team released a kit of this dual four barrel setup, as a regular production option in the beginning of 1956, which was a Ford dealer installed kit , and these provided some 1956 successes, including Chuck Daighís flying mile victory at Daytona. In the meantime Ford continued work on utilizing a supercharger or fuel injection system for the 1957 season.
Fordís 1956 sales campaign, which was essentially based upon safety, was not proving as successful as they had forecast and in a bid to turn this around, and hopefully dominate NASCAR racing during 1957, Fordís General Manager Robert McNamara purportedly committed $2.5 million to stock car racing. Robert McNamara wanted fuel injection, however Fords own engineers, and the engineers at Holley, failed to develop a reliable fuel injection system for the 1957 season, and so, because of concerns about reliability, Ford instead turned to superchargers. As H.A Matthias, the Ford Division Chief Engineer, reported in early 1957, ďWe have studied several types of new fuel systems. From the standpoints of dependability and ease of maintenance, it was decided that at present the supercharger offers the best system for obtaining increased performance at minimum weight penalty.
The decision to use superchargers was made late in 1956, and the decision to use McCulloch superchargers was probably due to the fact that Ford did not yet have a system of their own, and the fact that McCulloch superchargers were well proven in the field. Former Indy driver Peter DePaulo is often credited as being the person who suggested McCulloch superchargers to Ford in late 1956 however Ford was certainly already aware of McCulloch at that time, indeed one of the rumors that came from Detroit in 1955, and was reported in the Sept 1955 Motor Life magazine, was that the 1956 Ford Thunderbird would appear with either fuel injection or a McCulloch supercharger. McCulloch themselves reported in 1955 that Benson Ford had driven a McCulloch powered Thunderbird and was very impressed, and also reported in early 1956 that more than 50% of the VS57 supercharger installations were to Ford Thunderbirds.
The McCulloch VS57, which was already well proven by that time, did not meet Fordís needs, essentially due to the use of an internal oil supply for lubrication and cooling. The 300 horsepower plus that was a requirement for competitive NASCAR racing was right on the edge of the VS57ís capabilities, and coupled with the sustained high speeds of NASCAR racing there was some doubt as to the reliability of these units, as overheating would certainly have been considered a potential problem. The VS57ís previous competition involvements, which were essentially via drag racing did little to contradict these doubts, and many McCulloch VS57 units had failed in competition - generally as a result of them being pushed past their design limits. Regardless, at some time in 1956 Ford were shown the direct oiled VR57, which would have been at, or near, the end of itís development life, and ready for production, and were sufficiently impressed that they wisely engaged McCullochís Paxton Products for an exclusive one year contract for the VR57.
Phase I VR57 and 2-4 setup on a Fairlane at Daytona 1957 (Ford Motor Co.)
The 1957 homologation rules for NASCAR stipulated that only factory stockĒ engines could be raced during 1957. Factory ďstockĒ was defined as being advertised as a regular production option, and also required a minimum of 100 power plants being manufactured prior to the start of the race season, 1 January 1957. To meet these homologation requirements 100 - 125 VR57 units were delivered to Ford in December 1956, as a result of intense effort at Paxton . These were Phase I units, i.e. pre-production units, which differed from the later Phase II units. The Phase I blowers were sensitive, and suffered with unreliable control valves, although their performance was reputed to be a lot higher than the later Phase II blowers. They were also apparently tedious to work with, however they were never meant for use by the public, so this was tolerated. The most obvious difference with the Phase I is in the design of the case, which lacked the ribs of the later unit and used a large clamp instead of screws to hold the two parts together. Ford produced a total of 12 ďDĒ coded 1957 Thunderbirds in January 1957, and an unknown number of 1957 passenger and convertible cars using these first phase I VR57 units, which incidentally had serial numbers beginning with the designation VR57A, or Ford experimental serial numbers. Ford also pulled four C code 1957 Thunderbirds off the assembly line and sent them to Peter DePaulo, along with some phase I blowers, and DePaulo modified and prepared them for racing at the Daytona speedweek. These had the VR57ís installed and Iíll cover these and their achievements separately at a later date.
The Phase II VR57 (Ford Motor Co.)
With the homologation requirements met, further supercharged Ford production was not scheduled until later in 1957 when the Phase II VR57, a which produced nearly the same boost levels as the slightly larger Phase I units, were used. These were nearly as potent as the earlier Phase I units, and proved to be a lot easier to maintain and repair. The actual number of supercharged Fords produced in the Phase II production runs, are unknown, although between 208 and 211 of this production is believed to have been in the form of Thunderbirds, and a similar number (maybe as many as 300) were produced as Fords. All of the Phase II VR57 equipped Ford engines were designated as F code engines, and power outputs were 325 Hp @ 4,800 rpm or 340 Hp @ 5,300 rpm dependant upon the installed cam (256 or 290 degree duration), although Ford conservatively claimed only 300 Hp. Interestingly Paxton Products claimed that the output was actually 360 hp with the hotter cam.
Supercharged í57 Fords harass a Mercury at Daytona 1957
The VR57 equipped Fords basically dominated Motorsport during early 1957, and if it wasnít for the NASCAR ban on the use of superchargers (and fuel injection) from racing in April 1957 would probably have continued dominating for the rest of the season. A supercharged Ford even held the NHRA National title for three years. However, as happens with all good things, the use of superchargers was banned from NASCAR racing in April 1957. This ban, in conjunction with a ban on factory sponsored racing by the AMA in June 1957 effectively ended Fordís interest in the VR57, although F code engined Fords and Thunderbirds were produced to existing orders well after the June 1957 date.
As with all factory racing speed equipment the sales of the F code Thunderbirds and Fords was controlled, and the actual numbers produced were substantially less than the numbers ordered. This was particularly the case with the 1957 Thunderbirds as Ford was actively promoting the Thunderbirds as a Personal car, and not as a race car, and thus Ford did not encourage sales of the supercharged engine option, and purportedly even refused some sales . It seems very unlikely that Ford would have intended to produce the 1,500 cars required fully for NASCAR homologation, as politically racing was being de-emphasised at the time although in total Ford produced up to 520 VR57 supercharged vehicles in total.
Interestingly the successes of the factory built VR57 equipped Fordís and the difficulties in getting Ford to accept orders, for what was a $500 factory option, resulted in increased sales for the VS57 aftermarket units. Auto Mechanics of May 1957 suggested that rather than Ford dealers selling the just the traditional 2-4 racing packages as dealer options on the Fords, Ford had intended to offer a VS57 based racing package which could have been obtained in both single four barrel and dual four barrel forms, although this story has not been conformed elsewhere. This would also have further increased sales of the VS57, however the withdrawal from racing ended Fordís interest in supercharging, and the 2-4 racing package remained the only racing package offered by Ford, primarily because they had a stock of parts which they wished to use up.
When Ford withdrew from Factory sponsored racing in June 1957 they reallocated the remaining funds that had been allocated for racing development, and effectively cancelled all further development work with the VR57. The total number of VR57 Phase I and Phase II units shipped to Ford is unknown, along with the number of engines built with these superchargers, and the numbers actually installed. The Phase II VR57 units had serial numbers prefixed VR57A, the same as the majority of Phase I units (early Phase I units were numbered with experimental numbers prefixed XE, and without the VR57 designation), and the numbering sequence continued from the Phase I numbers. No more than 125 phase I units were delivered to Ford by Paxton and it is known that when Phase I units installed on Fords required repair, rather than replacing them with Phase I units from the stock that Ford held , they were replaced with Phase II units, and the Phase I units, when they were returned from repair, were reserved for Ford Thunderbird usage. The VR57A superchargers installed on the Thunderbirds always had a T stamped on the end of their serial numbers (i.e. VR57A301T), essentially as a means of indicating that they were intended for Thunderbird usage. Surviving VR57A serial numbers exceed the value 1200, which indicates that at least 1200 VR57 units were built by Paxton, assuming that the serial numbers were sequential. These were not all used to build engines with however, and Ford is believed to have produced less than 520 supercharged vehicles in total, as previously stated. It actually wasnít uncommon for a vehicle to have itís blower replaced several times, if that car was raced particularly hard, so a large number of replacements may have been made by Ford.
Paxton Products handled all Phase I VR57 repairs and rebuilds, so whenever a Phase I unit required repair it was replaced, and sent back to Paxton. The Phase II units were more serviceable, and servicing was handled by Fords Mechanics. When the superchargers were initially introduced it was discovered almost immediately that one could increase the supercharger output pressure by an additional 1-2 pounds by adjusting the control valve. Since Ford, and ultimately Paxton, was making good on the units, and the increase in boost could lead to failure of the superchargers, a lead seal, stamped with the initials Mc, was wired to the control valve on all units delivered to Ford by Paxton in a bid to prevent and/or indicate tampering. Ironically in order for the VR57 unit to be installed on the Thunderbirds the supercharger cover had to be rotated, which meant that the seal had to be broken by Ford, thus negating itís effectiveness.
The one year agreement with Paxton Products for the VR57 ended in September/October 1957, and on 1st November 1957 Paxton publicly announced that the VR57 would be available, with the serial number prefixed VR-57B, either without installation kit for $295.00, or with an installation kit for $495.00, for 352 cid 1958 Ford and 361 cid 1958 Edsel installations only. In actual fact the installation was the same for both engines, with only the scroll rotation being different between them. Paxton also announced that they did not intend to produce the VR57 to back-fit 1957 or earlier automobiles, with the possible exception of a few isolated models such as the Chrysler 300C and the 1957 Corvette. Instead they would continue offering the VS57 unit for general use. The VR57 actually had a greater air flow capacity than the VS57 units so I guess Paxton reserved the VR units for the newer larger V8 units being produced, which would have otherwise exceeded the capabilities of the VS57 units.
Paxton actually had a policy of using exiting components during installation, in order to minimize cost. So many VR installations by Paxton used VS57 idlers, pulleys and brackets, and the supercharger drive belts could either be the standard McCulloch 7/8 inch belts, or in some cases ĹĒ belts. As for the VS57A units intended for Thunderbirds, Paxton stamped a letter at the end of the serial number indicating the intended application, if it wasnít the standard Ford installation, i.e. CH for Chevrolet. Additionally the VR57B serial numbers did not continue on from the VR57A serial numbers, instead they started from 1 again.
Paxton Products produced the VR57 superchargers in limited numbers through the rest of 1957 and early 1958. Why production was limited was unknown, although the supercharger requirements of Studebaker and Packard, coupled with strong aftermarket sales of the VS57 units may well have heavily utilized Paxton,s production capacity. Servicing problems also existed with the VR57 units, basically because Paxton did not generate sufficient service information for these superchargers, and consequently from mid 1958 Paxton required all VR Superchargers to be returned to them for any warranty claims or rework.
VR58 Unit for Chevrolet and Corvette
Paxton introduced further improvements for the VR units during 1958. These improvements included high quality inner and outer races, Swiss steel balls, upgraded multiplier springs, and improved rear oil seal ring and the addition of an air deflector shield to deflect the boost output from the rear oil seal. The new VR units had serial numbers which started with the prefix VR58 and they were supplied by Paxton with a 4,000 mile, or 90 day warranty, which was valid only if the unit was not operated in excess of 5500 rpm with a standard 7.7 inch diameter crank pulley, and if the unit was not modified to generate more than five pounds of boost. As a reminder of this warranty the VR58 units were tagged with a warning that tampering with the boost pressure would invalidate the warranty. An optional oil filter, which greatly improved the superchargers life, was made available at the time of the VR58 introduction, basically as a safeguard against contaminated oil entering the supercharger. The VR58 was offered for the 348 cid 1958 Chevrolet, all 1955-58 Corvettes, the 1957-58 Chrysler 300, and the 1958 Fords, Edsels and Thunderbirds. Paxton fully intended that the VR58 supercharger would be available for all 1959 models however the continued popularity of the VS57, due to itís higher boost levels at low rpmís and the development of itís replacement, the short lived DO-VS59, stopped all further development.
In July 1959 Paxton discontinued the McCulloch VS57 replacing it with the direct oiled DO-VS59. This was initially introduced in 1958 and was essentially a VS57 modified to use direct oiling from the engine oil system, based on the experience gained by Paxton with the VR57/58. Paxton were sufficiently confident with the DO-VS59 that they offered a 1 year or 12,000 mile warranty with it, which was far more than the standard 3 month or 4,000 mile warranty offered with the VS57 and VR57B/58 units. The DO-VS59 was produced for all V8 installations, including new applications of the Edsel 410 cid, Mercury 383 cid and 430 cid, and the Lincoln and Thunderbird 430 cid engines. The VR58 kits were restricted to the 1958/59 Chevrolet 348 cid, 1958/59 Edsel and Ford 332 cid and 361 cid, and the Thunderbird 352 cid engines.
Paxton killed off the DO-VS59 in late 1959 or early 1960, replacing it with the fixed pulley SN60. Poor maintenance resulting in both variable pulley failures, and rusting due to the build up of engine blow by acid and water within the DO-VS59 units, being the main reason for the demise of the Variable Speed blowers. Improved seals, bearings and races allowed the planetary drives of the SN units to be driven at higher RPM, so the loss of low speed boost was partially compensated for by the ability to be able to drive the SN units with smaller diameter drive pulleys, giving higher impellor speeds, and higher boost.
Consequently from 1960 the VR58 was the only variable unit remaining in Paxtonís product line. The VR58 does not seem to suffer from the build up of blow by acid and water, that the DO-VS59 unit suffered from, presumably because itís internal design did not provide traps for these. Despite this Paxton continued no further development of the VR58, instead they concentrated on the SN60 and itís descendants. The VR58 was still offered, however, as a replacement unit through to the mid sixties, and was also offered through to 1970 in a modified form as racing supercharger. This variant (the VR5?) had the variable ratio planetary drive fixed in the high ratio via use of an adaptor, the oil control valve was replaced by an aluminum stud, and the supercharger was intended for drag racing usage only, retailing for about $250. The boost output could be modified (as is the case with all the VR units) by replacing the standard drive pulley with a different sized one.
Paxton dropped out of the supercharger business in 1971, concentrating instead on centrifugal blowers for industrial and marine applications. Ironically the VR supercharger survived this and was reworked as a blower for moving air through the cabins of submarines. These units had oil reservoirs mounted on the bottom, and were completely reworked as single speed blowers, producing a high volume of air at a low pressure of about 3 pounds. Two variants were made, each with different mount holes. No parts are usable from these, apart from the rear case of one of them (the B80S) which is interchangeable with the rear case of the original VR57 unit.
B80S Industrial/Marine Blower
The B80S produced 175 cfm of air flow and the rear case has proved to be very useful sometimes, as the mount posts are often cut off the cases when retrofitting a VR57 to another application, causing significant damage to what is a rare unit. The second variant, which has no useful parts, is ironically titled a VR70, although it is again a fixed ratio blower (3 to 1), and produces 400 cfm of air flow. No parts are usable from this blower with regards to the VR57/58 units.
VR70 Industrial/Marine Blower
When Paxton returned to supercharging in 1982, they unfortunately didnít resurrect the VR57/58 which I personally think is a great mistake on their part, and a great loss to the automotive world. A fire that occurred in 1984 at Paxton apparently destroyed much of their technical information, which probably would have included the VR57/58 information.