Minis with carburettor engines were always fitted with SU ('Skinners Union') carburettors.
There are however some different types of SUs used and it is sometimes neccesary to determine the type used.
They are determined by a simple coding system.
The first prefix (H, HD, HIF, etc.) determines the type, the following numbers the size.
The sizes describes the carb's diameter after the throttle plate on the engine side.
Size is always coded as follows: 1" + [number] / 8" = size in inches.
Example: HS4: 1" + 4/8" = 1 1/2" = 38,10mm.
Unfortunately these numbers are not cast into the carb.
So as following, some unique features to determine the type carb you have.
With the type and number/size you can order parts or whatever you want.
Different types of SU carburettors:
Lets start with the two types used most commonly on Minis.
Type HS
Float chamber fixed to carburettor body by a single (horizontal) bolt.
Flexible hose as feed for the jet assembly.
Available in 4 sizes:
- HS2 1 2/8" = 31,75 mm (vertical flange bolt pattern, narrow suction chamber)
- HS4 1 4/8" = 38,10 mm (angular flange bolt pattern)
- HS6 1 6/8" = 44,45 mm (4 flange bolt pattern)
- HS8 1 8/8" = 50,80 mm (4 flange bolt pattern?)
There are usually two carbs for each size carb:
With the float chamber attached either left or right hand, for twin carb setups.
Typ HIF
This type of carburettor has an integrated floatchamber.
Hence the acronym; HIF = Horizontal Integratet Float.
It features a sealed throttle spindle, and spiral returning springs on each end of the throttle spindle.
Available in 5 sizes:
- HIF4 1 4/8" = 38,10mm (angular flange bolt pattern [like HS4])
- HIF6 1 6/8" = 44,45mm (4 flange bolt pattern)
- HIF7 1 7/8" = 47,63mm (4 flange bolt pattern)
- [HIF38 = 38,00 mm] (4 flange bolt pattern)
- [HIF44 = 44,00 mm] (4 flange bolt pattern)
Note: the last two have a metric sized throat!
Less common types:
Type H
Float chamber attached to carburettor via a single bolt from underneath.
Another obvious feature is a long brass lever on the bottom side.
Available in 5 sizes:
- H1 1 1/8" = 28,58 mm
- H2 1 2/8" = 31,75 mm
- H4 1 4/8" = 38,10 mm
- H6 1 6/8" = 44,45 mm
- H8 1 8/8" = 50,80 mm
H4 were a popular modification in the 60's.
They are a bit longer than the HS type.
Type HD
Float chamber attached with 4 bolts from underneath.
Available in 3 sizes:
- HD4 1 4/8" = 38,10 mm
- HD6 1 6/8" = 44,45 mm
- HD8 1 8/8" = 50,80 mm
Jet sizes used:
There are two sizes of jets used on carburettors fitted to Minis (and Metros) by the factory:
- 0.090": HIF38, HS4, HS2
- 0.100": HIF44 , HS6
Applications:
Some commonly used carbs on specific engines/cars:
- 850cc engines pre 1974 single HS2 carb. Post '74 single HS4.
- 1000cc engines: single HS2 or HS4.
- 1100cc engines: HS4.
- Cooper S and Cooper had twin HS2 carburettors.
- Other 1300cc with HS4 (Clubman) or HS6.
- Cooper RSP/Mainstream: HIF44
- Metro 1000/Sprite: HIF38
- Metro 1300/MG Metro: HIF44
- Metro/ERA Turbo: HIF44 [different, special turbo carburettor]
What is a "Waxstat"!?
A Waxstat is the type of jet used after 1976.
It has a thermostat installed at the bottom, which moves the jet up or down,
depending on the outside temperature. It was introduced to make carbs less prone to
temperatures. Hence the movement of the jet alters the mixture a little bit.
Fixed jet to the left, waxstat jet to the right:
Waxstat jets are however only used (on Minis) with HS4 carbs.
To use a fixed jet on a carburettor equiped with a waxtstat you need either an adaptor or a different choke lever.
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I hope this is of some help to identify the mysterious piece of aluminum lurking under your Mini's bonnet
Tech-mods: you are free to correct spelling & information.
Maybe this can go to the FAQs (I think it's asked quite frequently
)?Regards,
Jan
Edited by Asphalt, 11 November 2009 - 03:06 PM.
