In adjusting things up in the engine bay, I noticed my carb, a Rochester B, would increase the idle when the throttle adjustment is screwed all the way in. I will be cleaning it out but was wondering if there is anything in particular to focus on for this problem. It's on a rebuilt 2.25, '72 Series 3. Thanks.
Rochester B
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I'm not familiar with the theory of operation of any of the particular carbs that work on the 2.25, but if it's that's the idle mixture screw that you're turning in to the point of cuttiing off the idle fuel supply and the engine is running higher and higher RPMs while you're adjusting it, then I'd look for fuel leakage on the primary fuel supply circuit that is continuously supplying fuel to the engine when it shouldn't be, for whatever reason.
I'd check to see that the fuel float isn't sticking open, forcing fuel through the system, linkages/cams for correct adjustment, etc.
What do your spark plugs look like? Black/sooty?
Again, this is based on the theory of operation of OTHER carbs plus your description of the issue, so it may or may not be applicable to your situation.--Mark
1973 SIII 109 RHD 2.5NA Diesel
0-54mph in just under 11.5 minutes
(9.7 minutes now that she's a 3-door).Comment
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Hooray, the Rover is much better, and the wife is much happier!!!
I'm referring back to the original reason for this thread; major vac leak(s), really rough idle, violent backfiring. Rebuilding the carb and sealing every possible vac leak spot seems to have helped loads. I now can adjust the idle and mix screws and actually get the truck to run differently. Vac pressure is now a steady 19-ish. I think I still need some fine tuning, however, so here are a few questions:
1. On a Roch. B, putting the mix screw in makes it leaner, correct?
2. For better, smoother acceleration, do I want it on the leaner or richer side of things?
3. The linkage all seems solid and the springs good, but the idle speed sometimes (too often) hangs too high and doesn't drop down. This is a fairly recent (the last 6 months). Lifting the pedal or pushing up on the throttle arm will drop it down, but that doesn't really help while on the road. Any thoughts or suggestions?
4. Will somebody please start making new Rochesters so we don't have to keep working on 1950s carbs?
Thanks for the past, present, and future help.Comment
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You'll want to run the mixture screw in as far as possible while still maintaining a smooth idle. Run it in until the engine starts to stumble, then back it out a quarter turn or so. Blip the throttle a few times and see where the whole thing sits.
Also make sure it's jetted properly for your altitude and you have the right plug for your compression ratio.
Where'd you get your rebuild kit?'67 sIIa 88Comment
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