Rochester 2GC running lean

by 76 Malibu Tue Jun 16, 2015 8:18 pm

I noticed when doing a tune-up recently that the plugs indicate my car is running lean. It also seems to have lost any "snap" at high loads or when you kick down the car. Anyone have any idea why the carb would lean out with time and how I can fix this? The car has a stock 2GC on a L65 350, all stock other than dual exhaust.

by pila Tue Jun 16, 2015 10:26 pm

Have you checked the inlet fuel filter on the carb ? Sometimes at highway speeds a partially clogged filter will meter the fuel to the carb...
Just an idea for you, but also you could remove the fuel line from the carb & check how much the fuel pump is putting out when cranking the engine ( with the IGN wire unhooked from the distributor) Your lean indication is not likely from idle speed, but from higher RPM on the road, where the demand for fuel is greatest etc...

by 76 Malibu Wed Jun 17, 2015 8:50 pm

Yes, the filter is new. Timing is set, vacuum advance, mechanical and total timing all good. New plugs, wires, and the car idles and runs great otherwise. It just has very little power in the high load/high RPMs. No hesitations just the car seems to weak and the plugs were showing that it is running lean.

A weak fuel pump is a good thought. This one is original, anyone know the spec these should be putting out?

by pila Wed Jun 17, 2015 11:50 pm

The manual I have for Chevys only says that "well defined spurts" of gas should come out when testing the volume of fuel being pumped. I suppose a small stream of fuel coming out would indicate that the pump isn't putting out enough volume.
Maybe a new pump will at least eliminate that possible problem...
If you do replace the pump, use a stock type. Some after-market types like Edelbrock , have a 7 PSI pressure, which you carb wont work with ( too much pressure))

by bracketchev1221 Thu Jun 18, 2015 11:11 am

Don't be so quick to declare the car lean by the plugs. Today's unleaded gases with ethanol sometimes DO NOT color the plugs like the old gas did. It used to be you expected a light brown color. Not anymore, unless it idles a lot, unleaded gas may leave no color.

by pila Thu Jun 18, 2015 2:00 pm

X2 on what Ray said.......

by 76 Malibu Thu Jun 18, 2015 8:41 pm

I am pretty sure the plugs are lean. They are very white and show some signs of excessive heat around the ceramic.

Maybe I should just overhaul the carb. Does anyone know if there are any decent quality carb kits left or is it just all offshore junk?

by pila Thu Jun 18, 2015 9:45 pm

Here is a place that has parts for the 2GC. I buy Q-jet parts from them.

http://quadrajetparts.com/shipping.php

by 76 Malibu Fri Jun 19, 2015 7:52 pm

Thanks for the info. The kits seem reasonably priced. Anyone know of any good info sources on 2G carbs? It be nice if I can retune this carb for a bit better performance. I know from the factory they were setup mainly for low emissions and as a result are much poorer than earlier 2G carbs.

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Rochester 2GC running lean

Rochester 2GC running lean

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