Triple SU's - Centre Carb Throttle Spindle ...

[838HNK]

Hi,

I'm dusting off a triple SU manifold and a collection of old SU bits to try to build up a working set. One thing that puzzles me is what the centre SU throttle spindle looks like. Does anyone have any photos or can offer any help of how the middle carb looks please ?? Also I assume I can use either a left hand or right hand float bowl carb for the centre one before I start ?

Cheers

Chris

[Allan L]

If you could tell us what engine is involved it might be easier to help. I presume it is a six-cylinder with separate inlet ports, but for SUs the breathing of such an engine is usually better with two carbs than three as the gas flow is more uniform.
Convention is to have SU float chambers ahead of the carb to avoid acceleration-induced mixture weakening.
The spindle question implies that you intend to couple the three spindles end-to-end but a good engineering solution is shown in this picture where the three carbs are controlled by links from a separate shaft.

Hope this is helpful.

[littleredrooster]

Allan L said:

The spindle question implies that you intend to couple the three spindles end-to-end but a good engineering solution is shown in this picture where the three carbs are controlled by links from a separate shaft.

Indeed - a far better setup. Even with twin carbs coupled shaft-to-shaft, the slightest bit of misalignment caused sticky throttles or rapid spindle wear. Three coupled this way doesn't bear thinking about. Adjustment is much easier, too.

Just remembered those little spring-steel U/J things that used to couple them. Ugh!

[838HNK]

The engine is a Ford Zodiac straight six and the manifold has three inlets with a balancer pipe.

The picture is very helpful and I think I have enough bits to have three matching carbs ... I also have the exhaust to go with the manifold so move form a single downdraft carb and log inlet manifold with a very restricted exhaust to triple SU's with a good extractor exhaust.

I'll fish all the bits out and start to mock it up ...

Thanks !

Chris

Edited by 838HNK on Sunday 10th May 16:22

[DB4DM]

If the engine is angled back, you may have to experiment with the float chamber heights to get the right fuel height in the jet tube. The manual for my car says float heights for each SU HD8 should be 7/16 inch but in practice the front and rear are set at 9/16 and the centre at 5/16. The engine is angled at 4.5 degrees up at the front

I have a 1994 edition of the SU Reference Catalogue which has data on some Ford conversions, eg Raymond Mays, if I can help

Edited by DB4DM on Sunday 10th May 16:53

[838HNK]

Thanks - I'll see how the engine sits once installed to see if its level. The jets and needles seem to be well documented but thanks.

A Mays head would be nice !! I think the original castings were porous and prone to cracking but new ones have been improved and recast ... Mines a Mk3 cast iron head but flowed and big valves ... I got the inlet manifold, exhaust and the rocker box from New Zealand as the Southern Hemisphere seems to be a better source for bits even including the postage. I've also sourced a spin on oil filter conversion and remote oil cooler. Cam will probably be a regrind of the original.

Edited by 838HNK on Sunday 10th May 18:28

Edited by 838HNK on Sunday 10th May 18:45