SU carburetters

[dave88sw]

Hi,

I'm looking for some help deciding which SU carb to use on my series 2.25.  I've managed to get hold of an adaptor to use an HS6 but I know very little about carburetters to be honest.  I've read a lot of the technical pages on the su carb companies website but understandably, they're written mostly as refurb information for existing applications.  Obviously, a 2.25 never left the factory with an su carb so i have no standard application to look at.

Am i right in thinking that they all had the same jet size and the needle was altered to suit the application?  Jets never seem to be labelled by size whenever i've seen rebuild kits so i assume they are all the same size.  Can anyone recommend a needle size to suit the 2.25 engine?

I know ACR do an HS6 conversion kit and supply the carb ready to go.  Does anybody know what needle/jet combination they use?  Seems cheeky asking them if i'm not going to buy it from them!

I also have an HS4c carb lying around which does fit the adaptor.  I was going to fit this as it actually came off a 2.25 but besides being seized up (ive freed most of it but the jet is seized), it appears to be quite difficult to find rebuild parts for the HS4c and I doubt it's big enough to supply the 2.25?

Any suggestions welcome, i've read so much information but i'm still none the wiser.

Thanks

Dave

[Bowie69]

I've successfully used a 1.75" carb on a 2.25, ran like a Swiss watch compared to the zenith.

I'm sure I found what needle it was too, will try and dig it out.

[Bowie69]

Found it, a BGB needle

I like the HIF44 to be honest, but all will work if 1.75".

[dave88sw]

This will be to replace a Webber 32/34dmtl set up off an early 90/110 that has been the most unreliable thing in the world so I'm hoping for swiss watch with the SU!!

You're a star, having found the ACR kit uses the HS6, i just assumed that would be the best option, i hadn't even considered the possibility of an HIF.  As it happens, my dads old 3.5 V8 with twin HIF6's (google tells me the HIF6 is 1.75" and the HIF44 is 44mm so effectively the same thing with most parts interchangeable) is sat in the garage, he's gone for megasquirt so they're spare. I'll find out what needles they have and take your suggestion of a BGB needle.

Thanks again!

Dave

[cackshifter]

The other thing is the spring, determining how far up the piston goes; most things seemed to use a red spring, but I seem to recall blue is lighter, yellow is stiffer

[neil110]

if you need any information about SU carbs, this is the place to go to.

 

http://sucarb.co.uk