I've been having some trouble with my SU HS6s - poor economy, low power requiring excessive choke use, blackened intakes, so I gave my pair of HIF6s another go. I've really wanted to use these due to the integrated float bowl, fuel temp compensation, and the overflow safety features.

I completely rebuilt the worse of the two carbs (#1) The kit did include new throttle shaft seals and just about everything else. (anyone know where I can find another kit - SU-23?) I installed them both yesterday afternoon. They take some extended cranking and choke to get started. I have to run with the choke for around 15 minutes before they'll idle okay. When warm, the car idles at 850-900 rpms. When I open the choke, the idle shoots up to around 2000-2500 rpms (difficult to control and only the front rebuilt carb has choke).

The real trouble is, when I go to accelerate they really lose power at around 1200-1800 rpms. Thsi leads to fals starts and stumbling acceleration. They sputter and I get a couple of pop/sneezes before the power kicks in. Reving the motor before I release the clutch or opening the choke helps get over the "weak spot." But I fear for my clutch plate.

from the lack of power, I'd think that the carbs were too lean, but the pop/sneeze and general "wetness" inside the carb makes me think too lean. Plus, when I lean out the mixture, the car promptly dies (This happened with the HS6s too).

Other symptoms include fuel consumption being around 10 mile/gal (also one of the reasons that I switched out the HS6s) and a lot more vibration to the motor.

From an earlier posting, I recall that there may be some issue with the HIF needles being too rich for a B18 (I have a leaner BAL needle in the rebuilt front carb - I need another), but I wanted to try it anyway. These are planned for use my transplant B20E as an interim while I get the Amazon D-Jet worked out. Frankly, I expected some excess fuel consumption, but I did not expect these things to run so poorly. Oddly, when I ran these last night, they had a little hesitation, but were defenitely giving better acceleration and the power was markerly more than the old HS6s.

Other Info.
This car has crane ignition (no points), cylinder compression readings between 130 and 140 PSI, generally upwards of 500,000 miles on the car with one previous B18 motor rebuild. I have new flange seals and a single box (140 style) air filter.

Anyway, I'm not a car whiz, but I can follow rebuid directions and have some intermediate automotive skills. Carbs are defenitely not my specialty and aside from balancing with a Unisych and adjusing idle, I'm not really great with them.

Any ideas on how I can improve the tune or why the HS6s have been running badly, would be greatly appreciated.

Thanks.

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1967 P220 (My every-other-daily driver...), 1971 P1800 (The Parts Car), 1972 145S (1993-1997), 1977 245 DL (1993-1999), 1983 245 (1998-2001), 1986 745 GLE (1997-2005), 1990 740 GL (2003-4), 1995 945 (2005-Present)....