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Discussion Starter · #1 ·
I rebuilt a set of 2 hole SU's off an older 122 and installed those but can't seem to get them running right. I was wondering if someone could tell me what a good starting point is for the mixture nut? I am 1 full turn out from the nut being seated all the way in. I notice I occasionally still get some light backfiring through the exhaust after turning the car off so its still a touch on the rich side.

Also, this barb in the top photo on the top of the carb body to the right of the piston chamber(?), do I leave this open? or block it off? I'm thinking it needs to be blocked bc the idle speed screw is all the way out on that carb and I had to increase speed on the right to get them almost balanced but was hoping someone could confirm.
125584




125583
 

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So that barb might be the vacuum source for the distributor. For tuning your of su's check out thr volvo green books. I believe they are available online if you look. Additionally Ron Kwas might be along later with more and better answers but he has a great website SW-EM Tech Articles that has a lot of great info for our volvos including SU carburetors.

Cheers
Daniel
 

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Yes, I’d block of that nipple, false air coming in there.
Here’s one if the experts. Ron has good info too.
 

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Discussion Starter · #4 ·
Awesome, thanks! Vacuum for the distributor makes sense, forgot they had that type. I'll check out the tech articles, block that barb off and go from there
 

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C;

Daniel has it right! That hose barb is for Distrib Vac. and can simply be plugged when using a Distrib which doesn't need it.

A good starting point for mixture is typically 2 turns/12 flats down...BUT that is only valid when the starting positions of Metering Needle is correct with shoulder level across bottom of Dashpot:


...AND... starting position of Jet is Level across Venturi. See: SW-EM SU carburetors

Your two (Air Cleaner) bolt carbs are good candidates for the Helicoil mod! See: SW-EM_SU Carb_adding_Threaded_Inserts_for_Air_Cleaner

Thanks for the reference, Dan and Craig!

Cheers
 
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