SU's - Fuel Rail - Flooding

[nospark]

Had a rear carb flooding problem with standard SU's. Used to happen occasionally but after this winters layup it was happening nearly every trip. The Hitachi Su's have fuel filters in the carb body. Standard SU's do not.

Blew compressed air through the fuel rail and added a small inline fuel filter between the fuel rail and carb. Problem solved. I post this up in case anyone running standard Su's has a problem. And everyone might need to consider flushing their fuel rails as its innards might start to becoming a bit flakey.

 

[jonbills]

Glad you're sorted.
Did you conclude that the problem was crud stopping the needle valve closing?

 

[nospark]

Yes Jon,
I've always had small bits of shrapnel at the bottom of my float bowls since i've had the car. I cleaned out the bowl and it flooded again shortly after and shrapnel had again appeared in the bowl. You might recall that I had a theory that the return fuel pipe system was causing my problem, which turned out to be daft. Only the rear carb flooded because most of the crud had probably congregated where the fuel rail turns back on itself.

Another thing i found out was that on SU's the valve needle seats come in two sizes of appature. There is little info on what type is used on each set up. Apparently the wide appature is used on single carb engines and on twin carb engines the smaller size is used. So important to find out you have the same sized appature for front and rear carb.

 

[jonbills]

Sounds like that's definitely it then.
The inlet valves on Dellortos and Webers I expect too are similar: the ,more engine there is per float chamber, the bigger the inlet valve.
When I was running an L24 I had 1.25mm inlets and now on the 2.9 I have 2.0mm inlets.