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What's this thing do...?
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Discussion Starter · #1 ·
I was running a '74 BBD on my '70 318. It has been running great even though the '74 BBD had not been rebuilt before I installed it. I grabbed it off the shelf from my son's car because my original BBD was not working at all.

I wanted to go back to the correct carb as far as the bowl vent was concerned and to get away from having so many blocked off, unused vacuum lines on the '74 carb. It had also started to leak and seep around the bowl and everywhere else it could.

I just put a commercially rebuilt '70 style BBD on. She fires right up and idles beautifully. When pushing the throttle the engine is instantly responsive and runs great.

I took it for a test drive and got around the driveway fine but at the end of my driveway is an uphill. As soon as I gave it more throttle to go up the hill, the engine immediately died. It started right up again and I drove back to the garage. The engine responds well to the throttle as long as it's not under load.

I can put the brakes on and put it in drive and put it under load and it will stumble and try to die when applying the throttle. As soon as I release the throttle before it dies it returns to a perfect idle.

I changed over the accelerator pump linkage and lever from my original '70 BBD because the new one was a little different and adjusted the pump to 9/16" as per the factory manual. I checked the timing and everything is well. The engine still starts perfectly. Idles perfectly. Is nicely responsive to the throttle without any load. But as soon as I give it a little load either by setting the brakes and accelerating in gear or by driving it, the engine will stumble and die or try to die when I give anything other than a very very careful, slow and steady acceleration.

Looking in the carb, there is plenty of spray from the accelerator pump down both throats. It's a nice atomized spray but there is a good amount. I can also see a good amount coming into the venturi when I flip the accelerator lever.

Is it possible the accelerator pump is flooding it out with too much?

What else might I look at with this carb?

I had no acceleration under load issues with the old carb and the only thing I did was change the carb.

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