I think there is a bit of confusion here.
There never was an HS1 SU - The HS range started at 1 1/4" HS2, as used on Minis, Minors 1100's etc.
There was an H1 which was an 1 1/8" SU that could be either horizontal or semi Downdraught, depending on what float chambers were fitted. The H series were available in H1 - 1 1/8, H2 - 1 1/4, H4 - 1 1/2, H6 - 1 3/4 & H8 - 2"
Kulled from Wikipedia for ease:
SU carburettors were supplied in several throat sizes in both Imperial (inch) and metric (millimetre) measurement.
The carburettor identification is made by letter prefix which indicates the float type:
"H": introduced in 1937 in which the float bowl has an arm cast into its base, which mounts to the bottom of the carburetor with a hollow bolt or banjo fitting. Fuel passes through the arm into the carburetor body. The bolt attaches to the carburetor body just behind the main jet assembly.
"HD": introduced in 1954 with the float bowl mounted with its arm fastening directly below, and concentric with, the main jet. The arm has a flange that fastens with 4 screws to the bottom of the carburetor, and sealed with a rubber diaphragm integral with the main jet.
"HS": introduced in 1958 the float bowl can be rigidly or rubber mounted to the main body, fuel is transferred by an external flexible pipe to the jet. The jet moves down to richen the mixture for cold starting,when the 'choke' linkage is pulled.
"HIF": (1982) the float bowl is horizontal and integral (hence the name) Horizontal Integral Float."HV" (1929), "OM" and "KIF" types also exist but were less commonly employed.[19]
The Imperial sizes include 1-1/8", 1-1/4", 1-1/2", 1-3/4", 1-7/8", and 2", although not every type (H, HD, HS, HIF) was offered in every size. There were also H models made in 2-1/4" and 2-1/2", now obsolete. Special purpose-built carburetors (Norman) were made as large as 3".
To determine the throat size from the serial number: If the final number (after one, two or three letters, beginning with H) has 1 digit, multiply this number by 1/8", then add 1". For example, if the serial number is HS6, the final number is 6: 6/8 = 3/4", add 1, total is 1-3/4", etc.
If the final number has 2 digits, it is the throat size in mm. For example, if the serial number is HIF38, the final number is 38, size is 38 mm etc.
Before the H, HS etc. There were the OM range, which were also either semi downdraught of horizontal depending on the float chamber employed. & were most commonly a 1" size.
In my opinion you can get away with an H series on a 7, but an HS series looks totally out of place as it is nearly 30 years to young for the application.
Lots of good info on the burlen fuel systems site. http://sucarb.co.uk/
There never was an HS1 SU - The HS range started at 1 1/4" HS2, as used on Minis, Minors 1100's etc.
There was an H1 which was an 1 1/8" SU that could be either horizontal or semi Downdraught, depending on what float chambers were fitted. The H series were available in H1 - 1 1/8, H2 - 1 1/4, H4 - 1 1/2, H6 - 1 3/4 & H8 - 2"
Kulled from Wikipedia for ease:
SU carburettors were supplied in several throat sizes in both Imperial (inch) and metric (millimetre) measurement.
The carburettor identification is made by letter prefix which indicates the float type:
"H": introduced in 1937 in which the float bowl has an arm cast into its base, which mounts to the bottom of the carburetor with a hollow bolt or banjo fitting. Fuel passes through the arm into the carburetor body. The bolt attaches to the carburetor body just behind the main jet assembly.
"HD": introduced in 1954 with the float bowl mounted with its arm fastening directly below, and concentric with, the main jet. The arm has a flange that fastens with 4 screws to the bottom of the carburetor, and sealed with a rubber diaphragm integral with the main jet.
"HS": introduced in 1958 the float bowl can be rigidly or rubber mounted to the main body, fuel is transferred by an external flexible pipe to the jet. The jet moves down to richen the mixture for cold starting,when the 'choke' linkage is pulled.
"HIF": (1982) the float bowl is horizontal and integral (hence the name) Horizontal Integral Float."HV" (1929), "OM" and "KIF" types also exist but were less commonly employed.[19]
The Imperial sizes include 1-1/8", 1-1/4", 1-1/2", 1-3/4", 1-7/8", and 2", although not every type (H, HD, HS, HIF) was offered in every size. There were also H models made in 2-1/4" and 2-1/2", now obsolete. Special purpose-built carburetors (Norman) were made as large as 3".
To determine the throat size from the serial number: If the final number (after one, two or three letters, beginning with H) has 1 digit, multiply this number by 1/8", then add 1". For example, if the serial number is HS6, the final number is 6: 6/8 = 3/4", add 1, total is 1-3/4", etc.
If the final number has 2 digits, it is the throat size in mm. For example, if the serial number is HIF38, the final number is 38, size is 38 mm etc.
Before the H, HS etc. There were the OM range, which were also either semi downdraught of horizontal depending on the float chamber employed. & were most commonly a 1" size.
In my opinion you can get away with an H series on a 7, but an HS series looks totally out of place as it is nearly 30 years to young for the application.
Lots of good info on the burlen fuel systems site. http://sucarb.co.uk/