Supercharged Kaiser’s

Henry J Kaisers venture into automobile manufacturing has been well documented, and consequently is not covered in detail here, instead I’ll just concentrate on the aspects of the Kaiser history which resulted in the eventual pioneering adoption of the McCulloch Supercharger.

Henry J Kaiser formed the Kaiser-Frazer Corporation in 1945, in conjunction with Joe Frazer of Graham-Paige, with the purpose of producing “the peoples car”, a cheap, light vehicle that everyone could afford. Economics of the time, as always, dictated otherwise and the resultant vehicles (Kaiser and Frazer) were priced in the medium price bracket along with Desoto, Oldsmobile and Buick, however the cars sold as the car starved public were practically buying anything. The cars that Kaiser produced were austere in appearance and innovative for the time, featuring passenger seating between the axles, a wide interior and full flow ventilation, however economies forced the use of conventional rear wheel drive instead of the originally envisaged front wheel drive. Engine power was provided by the 226 cid Continental six L head engine, which was originally designed for industrial use.

The first Manhattan (actually a Frazer and not a Kaiser) was produced in 1947 and this was innovative in that it was produced with a color-coordinated interior, a first for the time. Kaiser was also considering a V-8, and in fact had designed one in 1946, but tooling expenses were prohibitive, and Kaiser instead approached other manufacturers, having little success. Faced with the choice of going with the V-8, or having another attempt at his peoples car, Henry J Kaiser chose the latter, a decision which it is believed led to the eventual downfall of Kaiser, and the use of the McCulloch Supercharger.

The resultant peoples car, the Henry J (also marketed as the Allstate by Sears) , was produced in 1951 however the styling of the car was not to public taste, and sales were poor as a result. To reduce costs the Henry J had no trunk lid, no glove box and no ventilation system. Kaisers low volume production resulting in the pricing to be just below the Chevrolet, and this coupled with the fact that it was a plain car introduced when the public were craving for more chrome, contributed to the poor acceptance of the Henry J. At this time Kaiser had split with Frazer (dropping the Frazer range) and coupled with Willys, and the Henry J’s were powered by either a Willy’s 134 cid four or 161 cid six cylinder L head engine. In contrast to the Henry J, the 226 cid L head Kaiser which had been restyled by Howard ‘Dutch’ Darrin was very well received, particularly with regards to its attractive looks.

In 1953 Kaiser merged with Willys, and was by then in trouble, probably due to the poor Henry J sales. The 1953 Kaiser was however still a unique and attractive car, particularly in Manhattan form (reintroduced in 1952), but the lack of V-8 was making it a poor competitor when compared to other marques. Despite his troubles Kaiser courageously introduced the Dutch Darrin designed Kaiser Darrin in 1954, an expensive fiberglass bodied two seater sports car powered by the Willys 161 cid six cylinder F head engine. This also suffered poor sales further contributing towards Kaisers financial problems.

For 1954 Kaiser addressed the power problems of the Kaiser and it’s possible impact on sales by utilizing the McCulloch VS57 Supercharger on the 1954 Kaiser Manhattan. This raised the horsepower of the 226 cid L head engine from 118 hp to 140 hp reducing the 0-60 times from 17.5 seconds to 15.0 seconds for the manual transmission (19.5 seconds to 15.4 seconds for the hydra-drive transmission units). Rather than just bolting on the supercharger, as per standard McCulloch installations, Kaiser prudently carried some additional engine modifications although the beefing up the main bearings, larger valves with rotating tappets and a cleaned up manifold as reported by Motor Trend was not strictly true. A lot was made about all the improvements to the new super- charged engine but Kaiser-Willys was in deep trouble with the car end of the business by this time, and the only changes to the 226.2 engine was a cylinder head that now said 226 in place of supersonic, a coat of red paint in place of the older green, and a different style engine tag. The ONLY internal changes were high pressure bearings, both mains and rods. The valves were NOT enlarged, and Tappets were the same as used on all ’51-’55 Kaisers cars. The valve spring keepers were ball bearing equipped to provide a rotating action on the supercharged cars, in order to guarantee reliable operation of the engine, and referred to as rotators. During engine manufacture all components used were thoroughly inspected, and the completed power plants were extensively tested, probably to the extent that they were the most tested engines produced by any manufacturer of the time. As well as the supercharged 1954 Manhattan Kaiser is also believed to have produced at least one supercharged Darrin.

Publicity for the supercharged Kaiser was formally released in Detroit in early February 1954 and advance literature stated “Power on demand…yours with kaiser’s new Superpower engine. It’s like two outstanding engines in one…a thrifty low displacement engine for economical cruising, plus breath taking Super-power for the fastest pick-up you’ve ever felt! When you are cruising at normal speeds, your Superpower engine is loafing, providing economy that rivals that of the smallest cars. But when you press down on the accelerator, a tornado of pressurised oxygen pours into the engine, giving you a flashing burst of additional power almost instantly. Power to zoom up steep hills…to get away in a hurry…to pass safely! Power that will practically take you from under your hat! When you don’t need the extra power you don’t pay for it – either in gasoline or extra engine weight. What’s more you are assured of sea-level performance at highest altitudes…”

To aid Kaiser in supercharger publicity McCulloch sent their representative Al Harris to Kaiser-Willys publicity sessions in New York, Chicago, Atlanta and Oakland. McCulloch , in their in-house magazine ‘Flywheel’ reported on the subsequent press coverage of the Kaiser publicity as follows: “Newspaper and magazine writers called into publicity sessions were quick to see the impact of Kaiser’s new super-power engine on the automotive world. Creation of this new “power on demand” engine without major retooling problems and without any large increase in engine weight made good story material for automotive columns”. McCulloch also, as a part of their supercharger publicity campaign, entered a supercharged Manhattan into a 500 lap stock car race at Carrell Speedway on May 30, Memorial Day. Unfortunately after setting a qualifying time in 12th place among the 33 cars enteredfor the 250 mile endurance run, the Kaiser was forced out of the race at the end of 55 laps after a brusing mixup with another car which had resulted in damage to the Kaiser engine.

Press reception to the supercharged Kaiser Manhattan was positive. Quoting Bob Bergen in Econoscope, Los Angeles Mirror, January 29, 1954: “Biggest (Kaiser) advance, however, is an adaptation of the McCulloch supercharger, manufactured by McCulloch Motors of Los Angeles. Standard equipment on the deluxe Manhattan, it boosts the horsepower of the Kaiser’s 118 horse engine by 30%. Howard Grove, K-W’sWest Coast sales manager, pointed out that the supercharger keeps Kaiser in the horsepower race without sacrificing the car’straditional six-cylinder economy. With this device Kaiser has, in effect, stolen a march on the industry. Shareholders of the company will be interested in that retooling for engine adjustments to the supercharger cost only about $2,000,000. Retooling to build that much horsepower into the engine would have cost in the neighbourhood of $20,000,000. It gives the Manhattan a horsepower-to-weight ratio, according to my calculations,of 1 to 27. A test drive of this supercharger shows phenomenal scat.”

The use of the McCulloch supercharger was not enough to save Kaiser and as a result of financial problems the 1955 the Kaiser Manhattans ended up as very mildly reworked 1954 models. These were produced between January and April 1955 after a six month production hiatus, the differences between the two years are minimal being basically a different hood scoop (for the majority of 1955 models, although a few retained the 1954 scoop) and a new serial number plate. A further 1021 1955 Kaisers were built as a sample for a deal Kaiser made with the Argentine government to have the Kaiser built in Argentina, of these 1021 Kaisers 6 remained in the US and are believed to have had superchargers installed with the remainder shipped without superchargers.

Kaisers last production year in the United States was 1955, when the dies and machinery were shipped off to Argentina which resulted in the production of some 8,025 (reported by the IKA Club in Buenos Aires) non-supercharged Kaiser Carabela’s between 1958 and 1962. It has long been debated that if Henry J Kaiser had gone with the V8 instead of his Henry J peoples car, Kaiser would have certainly continued making unique and distinctive automobiles throughout the rest of the fifties, and maybe for even longer.

1954/55 Kaiser Manhattan

All 1954 Kaiser Mahattan’s sported the 226.2 cubic inch L head Continental engine producing 140 horsepower compared to the previous years un-supercharged 226.2 cubic inch engines 118 horsepower. To ensure reliability the 1954 engines were strengthened by using heavy duty bearings and exhaust valves, in conjunction with exhaust valve rotators. McCulloch worked closely with Kaiser engineering to provide the installation the cars ended up with.

1954 Production figures for the Manhattans are unclear and have been much debated. They are further complicated by the fact that the serial numbers allocated to the 1954 run did not differentiate between the 4 door and 2 door models. The serial numbers allocated range from K542-000001(or K542-001001) to  an estimated K542-005450  and the total number of 1954 Manhattans produced has been estimated as being from 4455 (4225 4 doors and 230 2 doors) to  5440, with much debate occurring as to whether bodies produced in 1954 were used on some or all of the 1955 Kaiser Manhattan production. All 1954 Manhattans were produced between January and June 1954.

1955 Production is more clearly defined due to the use of the Willys numbering system and was conducted after a six month break at the factory. Four door production used serial numbers ranging from 51367-5001 to 51367-5226 giving a total of 226 which were built between January and April 1955. A further single four door Manhattan (serial number 51367-11022) was built from the last Kaiser of the assembly line from the 1021 export model production and fitted with the supercharger (and all factory options, apparently for a K-W executive) increasing the number to 227. The two door production was 44 (serial numbers 51467-5001 to 51467-5044) built between January and February 1955, making them amongst the rarest of the Kaiser automobiles. It is not known whether bodies produced during 1954 were used for the 1955 Manhattan Kaiser production, although it is certainly believed so. The absence of high serial number 1954 Kaiser Manhattan survivors plus that fact that VIN plates on 1955 models are obvious replacements provide evidence towards this theory

A further 1021 1955 (serial numbers 51363-010001 to 51363-011021) unsupercharged Kaisers were built up until June 1955 as a sample for a deal Kaiser made with the Argentine government to have the Kaiser built in Argentina, of these1021 Exported Kaisers 6 remained in the US and are believed to have had superchargers installed. The remainder were shipped without superchargers, and none of the 8025 Kaisers built in Argentina as a result of the deal were supercharged either.

The addition of the supercharger to the Kaiser Manhattan allowed the Kaiser to accelerate from 0-60 in about 15 seconds, a 25% improvement on 1953’s figures, making it the second fastest six cylinder available during 1954. Contemporary road tests of the period reported the following:-

Motor Trend, April 1954

The McCulloch-blown engine starts instantly by turning the ignition key to the far right. Kaiser and McCulloch engineers have worked closely together to keep down the noise level of the supercharger for this stock car installation. They have succeeded so well that you may feel a little cheated after paying for this conversation piece that is so unobtrusive your passengers may never notice it; there’s no outward indication of this underhood surprise package either.

Performance-wise, though, they will know that there’s something very unusual about your new Kaiser. This years supercharged Manhattan with Hydra-Matic has at least 25 per cent better acceleration from a standing start than last year’s unblown version with same transmission. Improvement in the more important passing range is even better. Last year’s car took over a half-minute to get from 50 to 80 mph. Now it can be done in slightly under 20 seconds; this makes the Kaiser a much safer highway car for today’s traffic conditions. Another important safety consideration which only a supercharger can provide is that performance will hold up at altitude. Other, more powerful cars, will be hard pressed to match the Kaiser’s ability in the second half of a long mountain climb (like Pikes Peak) because they do not have forced air induction.

Motor Trend, September 1954

Ever since the day when Henry J. Kaiser jumped plumb into the automobile business with both feet, his products have been full of surprises. His merger with Willys slowed down both cars ’54 model announcements, but lots of people knew that the new Kaiser Manhattan, when it finally showed up, would have a supercharger – the first, incidentally, on a U.S. stock car since the Cord-like Graham departed this life back before World War II.

So, a far more eager crew descended upon our test Kaiser than usually greets a routine road-test car.

At the same time, Editor Walt Woron and Detroit Editor Don MacDonald were getting acquainted with another Manhattan in Toledo. The two cars made an interesting comparison, for they were equipped very differently. The California car had Hydra-Matic and power steering; the Ohio car, overdrive, standard steering, and tubeless tires.

Far and away the most interesting piece of equipment on both cars was the McCulloch supercharger. It is attached to an engine which is a lot like those on Motor-Trends ’53 Kaiser Manhattan and the ’54 Kaiser Special. Changes include prudent beefing-up of the main bearings, larger valves with rotating tappets, a cleaned-up manifold, and a new dual throat carburetor.

The closest approach to a whine we could get from this compact booster was a soft hum when we floored the throttle at around 40 mph, and that quickly died away. This discreet auditory response is no indication whatsoever of what is going on inside. One hundred and forty horsepower may no longer be an electrifying figure, but it’s an impressive one from an engine that has less displacement than any other engine in it’s price class or in the one below it, and is even smaller than a Chevrolet or a Ford V8.

What difference does the blower make to the guy behind the wheel? Much more at certain points than at others. From a standstill you can accelerate to a true 60 mph in 15.4 seconds with Hydra-Matic and 15.0 seconds with overdrive. At cruising speeds, the shift down to third gear in Hydra-Matic or overdrive, plus the stepped-up action of the blower, will take you safely out of harms way. Skipping from 50 to 80 in just 20 seconds, the new car will leave a ’53 (34.1 seconds) in the dust. That isn’t up there with Hamtramck hot rods like the Buick Century, but it’s not bad by any rating.

Kaiser makes the point that a supercharger just loafs along when you don’t need it (a solenoid on the throttle downshifts it, as it were, when you hit it hard). But even with the blower just along for the ride, as it was on our steady speed fuel checks at 30, 45, and 60 mph, the ’54 car didn’t begin to approach the miserliness of it’s ’53 counterpart. It registered anywhere from 2.2 to 6.7 mpg less, the larger difference being at the lower speeds.

Auto-Age, February 1955

Not since the days of the lamented Duesenberg and Auburn has America had a production passenger car with a supercharger. There have been a number of good reasons for this. Superchargers, or “blowers” as they are sometimes called, are relatively expensive, they cut down on gas mileage and in some instances, especially if they are in constant operation in a car, they tend to reduce engine life. Besides, most of our cars have engines so large that supercharging is just not necessary for ordinary highway driving. McCulloch Motor Corp., in Los Angeles, Calif., has come up with a new supercharger that solves most of these problems and Kaiser is taking full advantage of it, getting a jump on the industry, so to speak.

The new Kaiser Manhattan incorporates the McCulloch unit to raise its horsepower from 118 to a respectable 140. But gasoline mileage is still relatively unchanged; here’s why. The McCulloch blower has a “variable-speed drive” that allows it to mark time until you open the throttle all the way. This is operated by engine manifold pressure and thus gives you maximum power only when you need it for passing or hill-climbing. Most of the time the engine acts just the same as it would without the supercharger. In other words, the Kaiser Manhattan has a dual purpose engine; in normal operation it is an efficient and economical six-cylinder flathead, but when you really step on the gas it gives you all the jump of a large V-8 overhead-valve job. This, combined with optional Hydramatic drive or three-speed manual with or without overdrive, makes the Manhattan a right smooth and fast buggy.

It was on one of Ohio’s fine straight highways that I was able to clock the top speed of the supercharged Manhattan at 93 mph. At this time, too, I found useful passing acceleration by means of stepping down hard on the throttle (which throws the four speed Hydramatic into third speed). This moved the car from 50 to 80 mph (true speeds) in 14 seconds flat.

The McCulloch supercharger greatly increases this new Kaisers performance; it’s effect is felt immediately when you mash the throttle at any speed. Of course the supercharger (belt driven) does cut into the fuel mileage a bit at higher speeds, but even with Hydramatic our over-all mileage during tests was a reasonable 16.9 miles per gallon.

1954 Kaiser Darrin

Kaiser Darrin

Out of the 435 1954 Kaiser Darrins produced only three are believed to be supercharged (#2, #21 and #420), and even this number is under question (#378 may have been supercharged as well). Of the three supercharged Darrins, #2 is the only car to have factory documentation and is believed to have been built as a demonstrator. Walt Woron reported on a drive of a Darrin, probably #2,  in April 1954’s Motor Trend magazine. Kaiser built 62 prototype Darrins from the end of 1952 into 1953 an these used the “L” head version of the 161 cu in engine Factory information does make reference to the McCulloch being installed on prototype Darrins however It doesn’t say how many, and the H.P. ratings are left blank. Of the five or six prototype cars that have survived none are supercharged so the actual numbers modified by the factory are purely speculative.

The remaining supercharged Darrin’s are believed to have resulted from when Howard Darrin bought up fifty unfinished Darrin cars from the Jackson, Michigan plant in 1955 and took them to his shop in Hollywood, CA.  These he sold off from 1955 until 1958. The standard engine was the stock Willys “F” head 161 cubic six., although several were modified to fit a individual customers requirements. The optional engine for all the years that Howard Darrin sold the cars was the Cadillac Eldorado engine, but few Darrins were so equipped.  It is also believed that some Darrins were also fitted with McCulloch superchargers, and giving the close proximity of Howard Darrin’s shop to the McCulloch factory these modifications were likely to have been carried out by McCulloch Motors. Kaiser #420 is believed to have been one of these.

The use of the supercharger raised the horsepower of the Willis 161 cubic inch F head engine from 90 to 135.  Performance was reportedly around 10 seconds for the 0-60 time, a significant improvement on the 14 seconds achieved by the normally aspirated version. The one road test of the supercharged Darrin, carried out by Walt Woron for the April 1954 Motor Trend magazine, which was very favorable to the supercharged Darrin, reported the following:-

“When we request a road test or impression test car, we ask for a production model and that means not specially tuned. Despite this rule, though, we couldn’t get very upset when we found the only Darrin available to drive was an experimental job powered by a McCulloch-supercharged Willys F-Head.

On the road, we soon became aware of the McCulloch blower. Loafing along at 60 mph in overdrive (2500 rpm on the tach), we tromped down into direct which also kicks in the supercharger. The tach jumped to 3800 almost immediately and acceleration was only slightly less dramatic. The little Willys F-head was throatily at home in the unfamiliar region (for it) of 4500-plus rpm. In the background was the whine of the blower.

The 4.55 rear-axle ratio combined with overdrive and supercharger is tricky. Full throttle standing starts in low spin the wheels on any pavement, and when you do get going, you’re soon at rpms which aren’t healthy for a borrowed Willys engine. A normal shift to direct second is fairly fast, and you can stay floorboarded to about 50 mph before dropping down to direct high. This technique, if it can be called that, will consistently give 0-60 times in the neighborhood of 10 seconds. Considerably better results can be obtained if you want to risk speed shifting with a somewhat inadequate change lever.

A high gear downshift at 30 mph will bring you up to 60 in about 10 seconds, and we trimmed two seconds off this by using second overdrive, even though the supercharger is not fully operating under these conditions. Fifty to 80 mph in direct high is an easy 12 seconds.

The KD-161 can be taken over a particularly bad washboard road at respectable speeds. The low center-of-gravity keeps the car stable during severe corning and the instant power from the supercharged engine is ideal when corrective action is necessary. This was handy once when the rear end broke loose during an overzealous maneuver.

If Kaiser-Willys engineers and sales people decide to produce this car in supercharged form it will be very competitive to the Corvette in performance”

Manhattan Supercharger Installation

This was rather a neat installation with the supercharger mounted on the passenger side of the engine.  Noticeably the air cleaner is mounted to the lower left of the supercharger rather than to the right of the engine, and presumably this was to allow the supercharger to receive a cold air supply from under the car. To accommodate the supercharger drive belt the cooling fan was mounted forward slightly, otherwise all engine ancillary components remain in pretty much the same place as for the normally aspirated L head engines. McCulloch engineers worked in conjunction with the Kaiser engineers when designing the supercharger installation, however the September 1954 Motor Trend article was actually wong and the “beefing-up” main bearings was accomplished by the use of high pressure bearings only, both mains and rods. The valves were NOT enlarged, and Tappets were the same as used on all ’51-’55 Kaisers cars. The valve spring keepers were ball bearing equipped to provide a rotating action on the supercharged cars, and referred to as rotators. A lot was made about all the improvements to the new super- charged engine. But Kaiser-Willys was in deep trouble with the car end of the business by this time, and the only changes to the 226.2 engine was a cylinder head that now said 226 in place of supersonic, a coat of red paint in place of the older green, and a different style engine tag. The ONLY internal changes were the high pressure bearings and the rotator. Sound insulation in the engine bay was improved in order to reduce the intrusion of the supercharger whine into the passenger compartment, and it was often reported that many owners were disappointed that the supercharger was barely audible as they wanted others to hear what was under their hood. In fact the Kaiser supercharger installation was the quietest and most reliable supercharger installation of that decade, as one would expect for a luxury vehicle such as the Manhattan, and full credit should be given to the Kaiser (and McCulloch) engineers for producing it.

All Kaiser supercharger installations utilized the VS57B unit (Kaiser no: 215706) which was preset to four pounds boost and featured a 6 volt solenoid. The VS57B unit was only ever used on the Kaisers and not all of them were supplied with Kaiser badges. The use of a low boost level for the VS57B in conjunction with the modifications made to the engine by Kaiser pretty much guaranteed low stress levels for the engine, resulting in long engine life and high reliability. Most failures that occurred tended to be supercharger failure, and the majority of these were attributable directly to lack of regular oil changes to the supercharger. The supercharger itself was also relatively unstressed due to it’s low boost output setting and the low airflow demands of the engine.

The bracket mounts the blower rigidly on the left hand side (passenger side) of the engine and also serves as a mount for the belt tensioning pulley. The bracket was a cast item which carried the McCulloch serial number 736500, and Kaiser allocated the number 215708 for the bracket and 215707 for the idler pulley arm. The hoses shown in the last picture connect the intake for the supercharger to the air cleaner (flexible hose) and the supercharger output to the air box (straight re-enforced hose), and these carry Kaiser numbers 215720 and 215719 respectively.

The carburetor is mounted inside the airbox which provides equal pressure outside of the carburetor as well as inside, thus preventing the need to modify the carb for pressurisation. Note that with this airbox the kickdown switch used to activate the superchargers solenoid, and thus put it into high ratio, is located at the side of the airbox. This was generally the position used for automatics, as many of the later Kaisers were. The manual gearbox overdrive equipped Kaisers had the  kickdown switch located at the accelerator pedal. A lot of the airboxes also had a vacuum release or negative pressure valve in the air box, that could be sucked open by the carb to prevent stalling. These were about 1″ in diameter and were dealer installed. Part numbers associated with the airbox are 745591 for the top, and 745592 for the bottom. These are believed to be McCulloch numbers implying that McCulloch produced the air boxes for Kaiser.

Carburetor and Fuel Pump

The carburetor used on the supercharged Kaisers was the Carter WCD two barrel carburetor model 2146S (Kaiser no: 215727) . The same carb was used on both the 1954 and 1955 Kaisers with the choke being a thermostatic coil type. Venting on this carb is external, however as the carb was contained within the air box this would have not caused any problems. The fuel pump used was again Carter being the M2145S model (Kaiser no: 216121)  and was a camshaft operated diaphragm pump. This was a three valve pump with fuel line in and out, and a third line from the blower to the pump, boost referencing the pump. The pump maintained 4.5 PSI to the Carburetor at zero boost and the boost reference increased the pump output pressure in line with the boost pressure increase. The three valve design of the pump allowed for a greater fuel volume to be pumped.

The air cleaner used was an oil bath cleaner and was similar to the air cleaners shipped by McCulloch motors as a part of their kits during the early fifties. This was presumably designed in such a way that the chance of oil being sucked into the supercharger intake was minimized.

The crank pulley incorporated a groove for driving the power steering as well as the wider 71/2” diameter groove used to drive the supercharger. This was bolted to the harmonic dampener.  A fan spacer was used to move the cooling fan forward sufficiently in order to provide clearance for the supercharger drive belt. The drive belt used for the supercharger was the Daton S4537 and was 59.19 inches long when measured on its outside circumference. The McCulloch number for this belt was 37319 and the Kaiser number was 215718.

Darrin Supercharger Installation

The Darrin installations most notable difference to the Manhattan installation was the lack of an airbox, instead the carb was modified for pressurization using a low profile carb bonnet   (due to hood clearance). To install a VS57 on the Darrin, you have to relocate the oil filter to the opposite side of the engine.  The air cleaner is placed on the same side of the engine as the supercharger (passenger side) where the battery was originally located and the battery is moved to the drivers side and located on the frame under the steering column (very hard to service). The generator is relocated on the drivers side in order to allow room for the supercharger on the passenger side of the engine.

The bracket used to mount the supercharger is notably different to the one used on the Manhattan installation and looks to be cast aluminium. This mounts the blower lower on the engine, and more to the side, than that used for the Manhattan.

The Darrin carburettor linkage is very different from the Manhattans and mounting a switch on the linkage would have been unlikely. More likely would have been the use of the accelerator mounted switch in the case of the factory installation, and the manifold vacuum activated switch would likely have been used for the McCulloch installations.  McCulloch generally used electric fuel pumps on their installations, in conjunction with a boost referenced mechanical pump, and this is likely to be the case for a McCulloch installation. Darrin #420 has an electric fuel pump which further substantiates this. As for the factory installation it is likely that a modified fuel mechanical fuel pump was used, either of the three valve type like the Carter M2145S used on the Manhattans, or just a standard Darrin pump. These would have been modified to be boost referenced as per the 1954 Manhattan installations.

The carburetor used is a Carter single barrel carb, which would have been modified to accept pressurization via the carb bonnet. This modification would have involved sealing throttle and choke shafts, and sealing all external vents. Internal vents may have been required to replace the external vents to carb areas such as the float chamber.