Vacuum pipe on front SU

[Riv944]

Hi
Other than an introduction yesterday, this is my first post and first query. My car, a series 2 4.2 OTS bought in the USA thus normally with twin stranglebergs has had a triple SU set up put on and a Crane XR700 ignition. The engine runs very well and tick over smooth, plugs are a perfect light brown etc but I noticed today that the front carb has a vac pipe connector on it but it is just left open to the air. I assume the Crane needs no vac advance but should the pipe from the carb body be blocked?

Ian

70 series 2 OTS
65 Healey 3000

[christopher storey]

I'm afraid that the likelihood is that your ex Stromberg 4.2 has the wrong distributor for SUs . It should be a 41060A distributor with a vacuum advance capsule . . All the crane module does is replace the points and capacitor. Although your car will run without the vacuum advance, it will be distinctly short of part throttle response, and even more importantly , will suffer a considerable loss of fuel economy to the extent of about 10% . You need to obtain a reasonable example of the correct distributor and transfer your crane electronics to it to obtain the best results from your SU setup

[Riv944]

Hi Christopher
Thanks for the reply. I've checked the distributor and although I can't see what type it is, I can see that it has a vac advance module on it but there is no connection between the vac input on the dizzy and the vac pipe on the front SU. I'm new to the car and haven't yet had chance to drive it because it's not yet registered. The engine however starts easily and runs smoothly. Should I try connecting a pipe to give the dizzy some vac and see what happens? I've looked at the Crane manual and can't see any reference to vacuum, nor any other type of advance/retard system.

Ian

[Heuer]

For the cost involved it may be simpler just to replace the dizzy with one of these: http://www.simonbbc.com/distributors/6- ... ilter_id=5

[christopher storey]

Ian: the Stromberg equipped cars in some states had a retard capsule fitted, so you need to ID the distributor , and the capsule , positively before doing anything . It was all to do with early attempts at emission control and had a very deleterious effect on performance . The distributor number is cast into the body, and the capsule identifier is on the large diameter bit, and often needs cleaning with a wire brush before it can be seen.

[PeterCrespin]

.. The distributor number is cast into the body, and the capsule identifier is on the large diameter bit, and often needs cleaning with a wire brush before it can be seen.

No need to see any capsule identifier as the difference between vac advance and retard is very easy to spot.

The vac advance capsule has the vac connection on the side of the capsule furthest away from the dizzy - usually at the point of the capsule. Suction pulls the diaphragm and baseplate clockwise against rotation of the cam. The vac retard capsule has the connection at the other side of the diaphragm nearest the dizzy, so that vacuum pulls the diaphragm and baseplate anticlockwise to retard the opening point.

[christopher storey]

Thank you, Peter, for that very useful tip .

[Riv944]

Thanks Peter and Christopher for that information, I'd been struggling to see what the idents were with no success, it's not in an easy place is it?
I can however see from your description that it has a retard capsule, the vac connection faces the radiator, vac would pull the plate anti clockwise and it too is open to the atmosphere.
Strangly the dizzy looks to be new, there's no dirt or oil on the vac capsule. I'd have thought that when the PO put in the electronic ignition the correct dizzy would have been fitted, he didn't skimp on the renovation at all as far as I can see.
So where please do I go from here? What I thought was just a yes, block the vac outlet on the front carb or no, leave it alone seems to be getting deeper. Any advice welcome.

Thanks

Ian