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How to hook up twin carbs were single once lived...


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Posted

hi, need some help with fitting up some twin su's onto my l28 which currently has a single carb on it (from a patrol).

 

the fuel lines have got me the most stumped. i have marked them in red. i reckon L2 must be inlet, and similarly R3. but i don't know what R2 is and why it isn't on the left carb too.

and what is L1 and R1? fuel overflows/returns or something?

 

water is blue. will run without this i reckon.

yellow is PCV. how does this system normal get hooked up? thinking i might go without and just run filters on the crankcase and rocker cover, and block the pcv off.

green im thinking of sending to the auto. purple to the brake booster. should i send one of the other 2 vacuums to the dizzy, or is there a better spot for this?

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Posted

They're genuine 1 3/4" British SU's rather than Hitach / Datsun SU's as fitted to Zeds.

 

L2 / R3 are indeed fuel in.

 

L1 / R1 - I have these blocked off, I vaguely recall they may be for vacuum advance ???

 

R2 is fuel overflow (not a return, fuel only flows through here if there is a problem with the float chamber - sunken float / stuck valve / etc). The reason you don't have one on the other carb is probably due to the car they originally came off not having a fuel return. I have a number of different float chamber lids, with either 1, 2, or even 3 inlet/outlet pipes and with the inlet / outlets on varying angles. Not really a problem, just that if you have float issues, the fuel will run out of the carb / into the engine / wherever it wants to go, rather than running neatly out the proper overflow pipe.

 

Blue is water - not really needed in our Australian climate, its for warming the carbs on really cold morning starts in colder countries. Just block them off.

 

Purple is for brake booster - I don't have a Zed, so not sure what the other vacuum ports are for exactly.

 

Yellow is for the crancase ventilation - ie the big pipe sticking out the passenger side of the block. Run a hose from this pipe to the PCV valve (or block both off - I have and although others have suggested its not ideal, mine has been running that way for near 20 years).

 

Rocker cover breather runs back into the air cleaner normally, I run it into a catch can.

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