Anyone local to MA that knows SU carbs?: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Aug. 7, 2009 9:05 a.m. Mazdax605 Reader

Hey guys,

Some here may know my ongoing 78 Datsun 510/Stanza coupe project. I have been battling prioblems with the SU carbs I installed,and am at my wits end. No matter what I do they seem to be running rich. The car runs,and drives,but it is blowing smoke,and sometimes diesels when shutting down. Also it blows some nasty black soot out when first starting it up in the garage,and I am not sure if it is just water vapor in the muffler mixing with the rich mixture,but it isn't right,and I can't figure it out. My friend who is a Triupmh guy said he knows SU's pretty well,but it turns out he has no idea what to do with these japanese copies. I am trying to sell the car,but I just know it isn't going to happen anytime soon,so I may as well enjoy the car. I do drive it some,but the carbs are not right,and I would like to get them closer if not perfect. Any help would be much appreciated. I have a video on rebuilding,and tuning these carbs,but I am still having issues,and don't know where to turn.

Thanks,

Chris
Aug. 7, 2009 9:54 a.m. 44Dwarf Reader

pm sent
Aug. 7, 2009 10:00 a.m. 914Driver SuperDork

I bought SU rebuild kits for my 1966 1600 from these guys. The kit included a very good video on how to rebuild and tune it afterward. Maybe they'll sell you just the video.

http://www.ztherapy.com/

Dan
Aug. 7, 2009 10:35 a.m. Mazdax605 Reader

That is the video I have,but I am still having issues.

Turns out I really have no idea what I am doing.
Aug. 7, 2009 10:39 a.m. aeronca65t HalfDork

Call this guy.

http://www.joecurto.com/

He can help you out.

And remember, these carbs don't ned much fuel pressure. Otherwise you'll flood or run rich. I race with 2 lbs of pressure in my Sprite.
Aug. 9, 2009 11:03 a.m. mel_horn Dork

Dieselling when shutting down usually means a vacuum leak somewhere...
Aug. 9, 2009 11:51 a.m. senador New Reader

Aren't Click and Clack in Cambridge
Aug. 9, 2009 12:01 p.m. Datsun1500 HalfDork

Turn the screws all of the way in (clockwise). Turn them 2 and 1/2 turns out (counterclockwise). That should get you close. Make sure the needles are not sitting flush, they sit down about the thickness of a matchbook.

At that point you will be close enough to correct to rule out other issues. If after setting them as above you still have a problem, it is something other than the carbs
Aug. 9, 2009 6:10 p.m. Mazdax605 Reader

mel_horn wrote:

Dieselling when shutting down usually means a vacuum leak somewhere...

I was always told dieseling was from hot carbon deposits on the pistons that are igniting what ever little fuel is left in the cylinder. The funny thing is the car does always do it,but sometime it does.