80RX7LS

I recently sent my engine to Atkins for a rebuild, received the new unit and had it installed. The mechanic that installed the engine, a reputable foreign car specialist, also rebuilt the carb. After several months of adjusting and tuning we have the engine starting well and running. The engine starts quickly and idles smooth both cold and hot. The automatic choke circuit responds well to manual input and shuts off after the car reaches operating temperature. When driving the car, it pulls strong in 1st and 2nd gear and revs up to the desired shift points. The problem arises in the mid-range about 3K to 4K rpm. In that range there is a lack of power and then at around the 4K rpm range the secondaries kick in and the car pulls strong again. Additionally, there is a very slight 'hesitation' in this range but that is intermittent and not always present. However, occasionally the car seems to run fine through all the gears, pulling strong and revving as high as we care to. As points of reference the carb was rebuilt using an Atkins rebuild kit, it has the original jets, and the floats are set to FSM settings and are about in the middle of the sight glass. The fuel filter is new and because the power is there when the secondaries kick in, we believe the fuel pump and circuit is working well. This sound a little like the thread below titled 'SA Drivability problems' however my floats are adjusted where they should be, the jets are original and there is no backfiring occurring. At this point we're scratching our heads looking for a solution to the issue. And finally, one last bit of information is this is a 1980 SA with a stock 12 A engine and stock carb set up with the full rat's nest. One thing we have not done is any work with the Power Valve. Would this have any effect on the problem? Looking for any insight into this performance issue, thanks in advance for input.

mazdaverx713b

iTrader: (91)

Ed, are the needles and seats original? I know I've probably asked you but unfortunately I've forgotten. I've known issues to arise with the aftermarket needles and seats and wanted to touch on those as well.

80RX7LS

Hi Dave, good to hear from you. The jet assemblies are the originals, they are not from the rebuild kit.

80RX7LS

Dave, I want to follow up on my earlier reply and clarify my response. The jet assemblies are original, but the needle valve assemblies are from the Atkins rebuild kit. Sorry for any confusion.

diabolical1

iTrader: (3)

did you happen to keep the originals?

80RX7LS

Yes, we still have the originals. We originally had them installed but had problems with them seating and "flooding" of the fuel bowls. So, we replaced them with the Atkins parts and the fuel level issue went away.

Frogman

Fuel pump is my best bet