30ís Supercharger Technical

This section is basically a collection of notes and pictures , which will hopefully expand as new information is collated.

1939 McCulloch

Thanks to Tom for these pictures

1939 McCulloch

Heat Exchanger

A tap is taken from the input to the heat exchanger to the impellor housing. Another tap from the impellor housing is presumably connected back into the cars plumbing system. The 1937 onward V8's had the water outlets in the centre of the cylinder heads and this would mate up quite well with one of those.There is some debate as to the purpose of the heat exchanger. One school of thought is that it is used to heat up the air/fuel charge before it enters the intake in order to aid fuel vaporisation. Iím more inclined to believe that its an early form of intercooler as the compression of air that occurs during supercharging can increase the air temperature significantly. The flow of coolant around the impellor would cool the air charge during the compression phase and the coolant in the heat exchanger would similarly cool the fuel/air charge before it enters the intake. The cooler the fuel/air charge is the more dense it becomes, and therefore the more power can be extracted from it. Note the fins in the heat exchanger.

1939 McCulloch without Heat Exchanger

Not all 1939 McCullochís were fitted with heat exchangers. Iím not sure if the heat exchanger was as a result of product improvement or whether it was shipped as an option. The 39F model above has no heat exchanger although it does have cooling of the air in the impellor housing as indicated by the coolant connection on the impellor housing and on the casting that connects the supercharger output to the intake.

Grancor special heat exchanger connection.


Water Outlet on 1939 McCulloch

This picture shows clearly that the impellor housing is effectively double skinned, with coolant flow being completely around the impellor cavity. Its worth noticing that the version of this supercharger shown on the 1938 brochure does not have the impellor cooling. It may be that the 1938 models had no cooling whereas the 1939 models had impellor cooling and optional heat exhanger, or the cooling was an option for both years along with the heat exhanger.

Driveshaft Housing

This picture clearly shows the cam type bearing that the pulley driveshaft runs on. The bearing is actually submerged in oil from the gearbox oil supply. The mount for the driveshaft housing also acts as a return feed for the oil back into the oil valley under the intake.



The gearbox transfers the rotating of the drive pulley to the impellor via the impellor driveshaft. Note the external oil connection that splits the engine oil feed, with some being being fed directly to the impellor shaft bearing (which rotates substantially faster than the drive shaft), and the rest being fed to the gearbox and indirectly to the pulley drive shaft.


Oil Connections

The oil feed for the McCulloch can be seen at the base of the gearbox which was connected to the oil pump output?. I'm not sure about the oil connection at the base of the impellor housing, this is possibly a drain for excess oil back into the valley via the intake manifold.

The Impellor

This was driven via shaft from the gearbox. Given the flathead rpm levels and the boost output of the McCulloch Iím guessing that the drive ratio was somewhere in the region of 5 to 1. Its interesting that the later VS57 impellors featured the same design, albeit to a smaller scale.

Drive Pulley

Water Pump Pulley

Paul Schroud made up the pulleys shown in the photo for his 1937 unit installation, and also provided the diagram which should allow similar pulleys to be made up, although they are slightly different. He also reports ďTurns out that an 8RT pump pulley has the same standoff from the face of the block as the blower pully so it should be fairly straightforward machine work to add two more V-grooves behind that one.  My crank pulley groove is 1/2" but again the machine work shouldn't be too tough and there is room for the other two grooves behind the firstĒ.

Belt arrangement on Josh Zartmannís 1931 Ford 5 window coupe

Josh states "When I got mine the tensioner spring was broken so I ran a bolt through it and the gen. mount. Now its just a solid adjustable tensioner. Also mine pulls up on the inside of the belt and not down on the outside".  Its interesting that the 1937 models had the tensioner on the inside of the belt pushing up on the belts whereas the later ones had the tensioner on the outside pulling down on the belt as stated by Josh.


Belt arrangement on Grancor Special

Interestingly this has the tensioner on the inside of the belts pushing up on the belts which implies that this is the standard arrangement. Note the fixed pulley on the right hand side (from the engine front) which can also be seen on the earlier McCulloch belt setup in the picture below. Its also worth noting the generator location which differs between the earlier and later McCullochs.

Early McCulloch belt arrangement

1939 McCulloch Generator Mount and Belt Idler

Early generator location

As can be seen from this brochure scan the generator is mid mounted with the early McCullochs and is driven via a dedicated pulley at the rear of the input shaft. On the later ones the supercharger drive pulley had four grooves, three for the crank drive (and water pump drive), and one for the generator as can be seen in the Grancor special photographs above.

NOTE:-When putting an old style (pre '49) intake manifold on a new style ('49-'53) Ford flathead that you will have to vent the crankcase somehow.  It is as simple as removing the block mounted portion of the road tube (located under the intake manifold on the passenger's front side of the valley) and the fuel pump pushrod and remounting the fuel pump/crankcase vent from the old style manifold.  This obviously requires the use of an electric fuel pump.  If you don't vent the crankcase you blow the front seal and get the mess seen under my motor on your garage floor!!!!  Not good, plus you have to replace the seal!