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MG MGB Technical - daul SU conversion


I'm working on a dual SU HIF swap for my 1980 LE. Right now I'm getting close to being able to start it for the first time with the new carbs, but need some help with the fuel line setup. The Zenith carb used a 5/16" supply line whereas the SUs need 1.4". Is there a reducer that I can buy that will hook onto the 5/16" line coming out of the fuel filter that will let me connect to the SU's 1/4" fitting?

Thanks,
Dave
David Plantz

I never noticed that problem when I converted to HS4s.
Stu Rodger


Hi, Stu

It's definately a smaller diameter hose size. I've also not heard of anyone having issues with this. Maybe some Zenith carbs had the smaller fuel line fitting size?

Thanks,
Dave
David Plantz

You could use a fuel filter and squeeze the smaller pipe onto the output of the filter with the bigger pipe going in. That should work. Just use proper hose clamps to secure everything properly.
Ross Kelly

A 72-74 filter to carb hose should work. Moss #376-930.

Clifton
Clifton Gordon

David,

when fitting new carbs a new filter seems to be a good idea too and this will solve your problem with the fuel line.

Take care of the vac pipe to the dizzy! Most cars with twin SU carbs run ported vacuum insted of manifold vacuum, as used on the Zenith installation.
May be you will have to modify your dizzy too or fit one that was usually used with the SU setup on LC a engine!

Ralph
Ralph



Ross and Clifton:

Thanks! It sounds like either suggestion will work for the hose. I thought the earlier cars had the 5/16" fittings at the fuel filter as well.

Ralph:

My car has a 25 D distributor on it now. After looking at my '74 GT, I've found that the vacuum supply for the dist'r comes off of the intake, so wouldn't that work for this car?

What were the main differences in the later distributors besides the fact that they had the electronic bits inside instead of points?

Thanks!
David
David Plantz

This thread was discussed between 05/05/2008 and 07/05/2008

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