Morris Minor Owners Club

Hi All

I am a newbie on this forum although I am used to forums from my other car. Anyway I am restoring a 1967 2 door and am fitting a Marina 1275 engine. I have sourced a 1 3/4 inch SU carb (HS6 with separate float chamber) as I am led to believe this works well with the 1275 engine.

I have never worked on a Carb before so bear with me if some of this is obvious to you. Having looked at the SU website I believe the carb I have was fitted to a 1.5 Allegro or Maxi and I have no idea what the needle, piston spring or jet are.

1 - Somewhere I have read that all jets in the SU carb are the same - is this right or do I need to change it to suit this engine ?

2 - secondly if I am running the 1275 engine (Standard) with the hs6 1 3/4 inch carb what needle size do i need

3 - do I need to change the piston spring while I am at it?

All help is most welcome as I am trying to get the engine side of things sorted while my bodyshell is going to the paint shop.

Hello Merlin,

"1 - Somewhere I have read that all jets in the SU carb are the same - is this right or do I need to change it to suit this engine ?"

Yes, as far as you are concerned it is true, there are actually different jets for different sizes of carburettors but for mixture setting it is all done with the needle\spring.

Have a look at this programme which gives a very good guide:- http://www.winsu.co.uk/

In practice, few people bother much about the spring, merely changing the needle, of which there are dozens, each identified by a letter code (Not size like conventional jets). When you change a needle it needs fitting with it's shoulder flush to the base of the piston.

Alec

The 1275 engines in single carb form were fitted with HS4 carbs so the reference book does not list a needle for the HS6 on a 1275. Best bet is to try what you have and then change it if not suitable. http://www.mintylamb.co.uk/suneedle will compare different needles. The needle code is marked on the shank and if your eyesight is as good as mine then you will need a magnifying glass

Hello Mike,

that is the beauty of the Winsu programme, it gives non standard set ups.

Alec

BDL needle is a good starting point - but what needle is in the carb at the moment? It may be fine. The spring (obviously I think) holds the piston down. On a standard 1275 engine the one you have may be a bit too strong - but try it and see ! Really the only way to find out is to try a lighter one (or cut a coil off the one you have) - see how it goes.

Thanks for getting back so quickly and for the advice

firstly the existing needle in the HS6 is a BAS

I have a few other SU carbs kicking about so checked their needles and have a BDW and an ADG - the others are at my fathers so will have to check them when I get chance.

I tried the WinSU program all is well but I dont know the final drive ratio of the car. In the driveline everything is standard except I have the 1275 engine and a ford type 9 gearbox conversion - any rough ideas? I see that the program needs registering to see the needle selection available so will have to look into that when I get a chance.

Hello Merlin,
although it will be obvious when you come to try them, you can only use needles from an other 1 3/4" S.U..

Alec

As above - only needles Bxx can be used in the larger carb. Try the ones you have - they may be fine. BDL is a general upgrade needle used on 1275 engines.

Enter the needles in the mintylamb website and it will draw you a comparison chart.

Thanks guys

Tried the Minty lamb website and the suggested BDL needle looks like the one to go for so will get hold of one and give it a try. Might be a while before I get that far as the car is just a shell at the moment - cant wait to get into final assembly - its been a long journey.

I recently purchased a jet for my 1 3/4 Hif (went for cheap again), and i presumed that the jets were the same for all the 1 3/4 carbs. But they are not, it seems. The one I purchased, the hole down the jet tube is 0.1inch as apposed to the more common 0.09inch.

Does anyone know what range of needles I would need for this jet.
To be fair, the car runs ok and have a little more torque at higher speeds than the 1 1/2 hif with AAA needle.

100 jet is correct for the HIF 44.

Many thanks BMC. I now realise the jet size is listed in my 'MORRIS ITAL' manual (0.1 inch)

The SU web site seems to list the smaller jet in the kits for this engine. I now realise you have to select the correct jet and needle manually in the options boxes and not go with the default.

OK guys I have come into another issue with the HS6 carb I have. The float chamber is at the wrong angle in relation to the carb body as when the carb is bolted to the manifold the float bowl is not vertical.

There is a float bowl chamber adapter between the carb and the float chamber - part number AUD 2063 and I need to find out the right part number to give the correct angle for the float bowl when bolted to the A series 1 3/4 inch manifold - any ideas?

Try turning that adapter over- does that help? Or attack it with a file or even a hacksaw! It's just a spacer - nothing high-tech about it.

As you have discovered, SU carbs come in side draught or semi downdraught of varying angles, depending on the angle of the float chamber relative to the carb. For obvious reasons the carb must be installed with the float chamber vertical. A Series engines are usually semi downdraught[frame][/frame]
Take your pick from this lot

Hello Merlin,

there is a range of these adapters for right and left hand carburettors and at different angles. (As shown above)
Contact Burlen, http://www.burlen.co.uk/, they'll provide the correct adapter.

Alec

when i had this problem with a HS4, i did as bmc says, and took a hacksaw to it!

thats the list I found on the su site - just wondered if anyone knew which one was the right one to choose - think the AUD 2071 might be the way to go