H1 SU versus Ruby Zenith sidedraft

[Hugh Barnes]

I think the 1" is the OM...

[Bob Culver]

The carbs carry little or no designation so the type is a  mystery to most . I am not sure but understand the H alone is 1 inch., the diameter at the output. H2 is 1 2/8. Earlier without oil dashpot were OM etc but I dunno the exact distinctions.
Some early had horizontal mount holes and fitted directly.

[Greig Smith]

For what it's worth we fitted a 1 1/8" to Dad's 1930 Triumph Super 7 in place of the old updraft Zenith and it made a world of difference. The car is now useable in modem traffic, much more get-up-and-go.

In fairness the Zenith was pretty worn, so I modified a damaged spare updraft manifold with a flange to take the side draught SU, the original manifold and Zenith is in the Triumph spares for the next custodian after I pop my clogs

Car starts on the button, is smooth and progressive right throughout the rev range and the pick up in power is markedly improved. It runs a high ratio diff and close ratio 3 speed box, so pull away was always a fiddle with the Zenith. It's a joy to drive and we are no longer a mobile chicane on the roads.

We run a pair of 1 1/8" SU's on the A7 race car with a balance pipe between them, engine reeves freely to 6 grand where I chicken out. I'm a big fan of SU's despite all my Alfa's running either Webers or Solexes

Aye
Greig

[Chris KC]

For me the big advantage of an SU is once set up you can forget about it. Mine came from a jumble sale for £1, was cleaned up with paraffin and went on the car.  Thus I must say £250 sounds an awful lot to me.

Chris, I'm happy to pay a quid commission too if you manage to find another one....

I picked up a 1 1/4" HS2 at Beaulieu yesterday - it's old enough to have a brass dashpot top and needs a bath in WD40, but recoverable I think. Together with a 4-speed A7 gearbox top / gear lever set me back £15. Inflation!

[Parazine]

There are two 1" SU types commonly available, the OM, which has a round air intake and no intake flange and the UBA, which has an intake flange suitable for an air filter. UBA's have a vertical mounting arrangement, so need an adapter to mount onto an A7 manifold. They were standard on late Morris Minor and early Morris 8 models but may have been fitted to other, less common vehicles.
OM's are more variable and some have a horizontal mounting and bolt directly onto an A7 manifold.
Fitting an SU to an early car is a bit of a challenge, requiring a special inlet manifold. I have a UBA on my mag engine Chummy, using a manifold fabricated from 28mm plumbing fittings! It just about allows the SU to fit in and close the bonnet. However, I have obtained a Derrington aluminium manifold, which gains about an inch over my creation. Sadly, it is cracked and probably only suitable as a pattern. I may see about getting some reproductions cast.........

[AllAlloyCup]

  F4B20BB9-1B31-415C-88E7-5E5AE31485FB.jpeg (Size: 143.4 KB / Downloads: 155)

Just picked up an OM in good nick on E-xxx
For £25, very neat fit on a Ruby manifold.

There was another one for £35 listed

No adapter needed with this version.

Seems AN is the needle to go for?
I have a steel crank, slipper pistons,
But so far am planning to use standard
Cam and followers. Any practical advice appreciated
As I’ve never built an Austin 7 engine before.
It’s an 1 1/8” two bearing coil engine.

Bill G

[JonE]

is it still there, Bill? trying to find these things is all down to what words one searches on!

[Hugh Barnes]

AN needle is what I use. I have also dabbled with a GG..

AN is a good place to start...

[AllAlloyCup]

Hi JonE
There’s another on E-.... for £169 or offer just now but it has the flanges that need an adaptor and an aircleaner
Add Classic to the search terms I gave you,

Bill

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Hi High thanks for the needle tip:-)

Bill G

[Chris KC]

Adaptors to the inlet manifold used to be available from usual sources but if not they are easily enough fabricated. Wouldn't worry too much about the air cleaner.