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Old 07-11-2003, 09:17 PM
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rochester 4 jet carb, rich

New to the board and have a ? about a rochester 4 barrel carb. The carb is the stock carb on a 67 chevy c-10. I am having problems with the carb running rich. It has sat for about 20 years and I am trying to get it going well enough to pass emissions.
The truck was my Granddads and I got it when he passed on. I have since changed all the fluids,plugs, wires, cap, rotor, points, and set the dwell, timing and idle speed. As well I fixed all the vaccum leaks and rebuilt the carb. After I got it running I was putting out black smoke. I ended up pulling the top back off the carb and found that the level and the float drop were very different from what I had set them at, the floats were riding about 1/4" higher and the drop was about 1/2" lower. I reset them and reinstalled the horn but it is still running rich.
The other suspect in the carb is the jets, I would not be surprised if they had been changed or drilled. They are stamped 59 in the primaries and 68 in the secondaries. Do these numbers correspond to drill sizes? if so I can pull and check them.

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Old 07-13-2003, 03:23 AM
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I don't think the jet numbers are drill sizes, but I can't say for sure. The Doug Roe book Rochester Carburetors has a chapter on the 4G carburetors. Check it out.
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Old 07-13-2003, 09:42 AM
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Please go to the Knowledge Base and plug in .. rochester carb and you will get quite a few sites that will tell you how to adjust and work on one.
Luv the smell of NITRO in the morning.
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