Single Seater SU Carb Position

[Malcolm Parker]

The single seater is getting to the stage where it is nearly driveable.  The engine has a Pigsty 4 into 1 exhaust manifold ( the only Pigsty part on it!) and I have an ALR semi downdraught inlet manifold which has been in the cupboard for years.  The intention is to put a 1 and 1/8" SU on the engine.
When I put the manifold on with the necessary spacer/adapter so that the carb is above the exhaust (ie semi downdraught), I find that there is not room for the choke mechanism to open as it only just clears the exhaust, this being slightly upswept.
I have inverted the inlet manifold so that it is now semi updraught and fitted the carb, having reversed the position of the float chamber.
The carb now fits but there is only about 1/4" between the oil damper top and the exhaust.  On the plus side the float cha             mber is not directly over the hot exhaust and the installation is neat, not requiring a modified bonnet top.   Also the car is based on Mrs Jo-Jo which had updraught carb(s).
I would welcome comments and advice.  I think I have seen some discussion about whether it is wise to have the float chamber behind the carb.  I would stress that at the moment i am only looking at getting the car running, the fancy engine will have to wait.  I like the fact that the updraught set up will keep the bonnet line clean and free from big holes and bulges and carb parts sticking out.

[Steve Jones]

I think you need a float chamber that 'twists' the other way from the one fitted so it can be mounted in front of the carb body. I've put one out to bring with me on Saturday. Also, have a look at Graham's car on Saturday. Twin carbs but, essentially, similar.

Steve

[Howard Wright]

Hi Malcolm

I twisted the carb on my special forwards (intake towards the rad). Made all sorts of complexity getting the float chamber in the right orientation and level. I ended up separating the float bowl and connecting it via a short steel pipe to the carb with an aluminium cylinder extending the fuel intake.  I also had to have an elbow tig welded to the sports manifold. Seems to be working quite well so far (250 miles).

Cheers

Howard

[Reckless Rat]

By reversing the orientation of the carb body relative to the float chamber are you going to have problems with the carb flooding, as the fuel level appears to be going to be much higher than the main jet?

[Howard Wright]

Hi Reckers

Yes. I had huge problems getting the float level right.  This isn’t the final incarnation (the float chamber ended up on the other side!) but it gives you an idea of the need to drop the float level using the aluminium cylinder.  The manifold is a first attempt. I brazed the T and flange on but I wasn’t happy and had it professionally Tig welded.

Cheers

Howard

[Alan]

Yes that’s right, you will. You need to lower the float chamber as well as mount it forwards of the carb body. I think Malcolm already knows that. Why does my spell checker want to change Malcolm into malcontent?

[Charles P]

 Why does my spell checker want to change Malcolm into malcontent?

Highly advanced AI

[Steve Jones]

Why does my spell checker want to change Malcolm into malcontent?

It's because it tuned into the phone conversation he and I had at lunchtime today

Steve

[Terrytuned]

Malcolm my s/seater is using a H4 SU but had the same float chamber fuel height problems, so I remote mounted it,I also put a spacer between the bottom feed fitting and the carb body as when it was hot it dripped fuel from the intake which the startline marshals thought was a fuel leak. I set the fuel height up on the bench with the carb fitted on a spare inlet manifold fed by a test tank so when the choke is operated petrol just flows over top of the jet when it is set 8 flats down from the bridge, the chamber level set to standard fuel level height.
Hope this helps you setup. Terry.

Don't know why the site turns some photo round.