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Joined: Feb 2011
Posts: 135
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Feb 2011
Posts: 135 |
Thanks for the info Oldie... I was holding a tapered brass cone in the manifold port as I was reading the gauge. The movement was minor.....kinda like an old speedometer. I fugured it was normal.
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Joined: Feb 2011
Posts: 135
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Feb 2011
Posts: 135 |
Well, I might be on to something tonight. I tried swapping carbs as I have another W-1 (420S). It fired right up and ran much smoother right off the bat. After a minute or two of tweeking it was the happiest with the mixture screw 2 turns out and running at a smooth 500rpms. The excelerator pump is either worn or needed to swell so it didn't rev up as nice as the first carb, but I could definitely tell the idle was lower and smoother. I'm thinking with a bit more playing around and the engine at operating temperature I would be able to bring it down a little more. That said it seems as if the idle circut on the OE carb isn't letting enough fuel in resulting is a lean condition.
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Joined: Nov 2002
Posts: 7,472 Likes: 26
ChatMaster - 7,000
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ChatMaster - 7,000
Joined: Nov 2002
Posts: 7,472 Likes: 26 |
In your first post you indicated you had the idle mixture screw all the way in. If that's the case it certainly will not let in enough fuel, or gas to get a proper mixture at idle.
Steve D
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Joined: Feb 2011
Posts: 135
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Feb 2011
Posts: 135 |
Yeah, that does sound contradictory. I'm a little over my head on the inner workings of the idle circuit but someone told me that the mixture screw only controls the flow of air in the circuit and not gas. So, if the fuel flow was being limited you would have to reduce the amount of air to get the right mixture otherwise it would be running lean. That's where I made the conclusion.
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Joined: Mar 2012
Posts: 151
Shade Tree Mechanic
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Shade Tree Mechanic
Joined: Mar 2012
Posts: 151 |
Have you checked for manifold gasket leaks?Leaks from the manifold can act like carb problems.I had to have my exhaust manifold planed down because it was warped.Car ran 100% better.
kerry j camp
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Joined: Dec 2001
Posts: 10,379 Likes: 1
Technical Advisor ChatMaster - 10,000
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Technical Advisor ChatMaster - 10,000
Joined: Dec 2001
Posts: 10,379 Likes: 1 |
Excellent advice. You can check by WD-40 or a vacuum gauge.  
RAY Chevradioman http://www.vccacolumbiariverregion.org/1925 Superior K Roadster 1928 Convertible, Sport, Cabriolet 1933 Eagle, Coupe 1941 Master Deluxe 5-Passenger Coupe 1950 Styleline Deluxe 4-Door Sedan 1950 Styleline Deluxe Convertible 2002 Pontiac, Montana, Passenger Van 2014 Impala, 4-Door Sedan, White Diamond, LTZ 2017 Silverado, Double Cab, Z71, 4X4, White, Standard Bed, LTZ If you need a shoulder to cry on, pull off to the side of the road. Death is the number 1 killer in the world.
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Joined: Nov 2001
Posts: 19,758 Likes: 64
ChatMaster - 15,000
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ChatMaster - 15,000
Joined: Nov 2001
Posts: 19,758 Likes: 64 |
Manifold vacuum of 16-17 suggests that the valves are not leaking and the intake manifold is not leaking. However it would have been far better to be able to measure the vacuum at ~200 lower rpm.
How Sweet the roar of a Chevy four!
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Joined: Feb 2011
Posts: 135
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Feb 2011
Posts: 135 |
Update....the carb has been looked over and the low speed idle tube was not sealed correctly at the tapered brass tip. This resulted in a poor vacuum signal in the idle circuit. Apparently the service manual recommends replacing the tube when rebuilding and mine was not. I don't have it back yet, but is sounds like a smooth idling engine is in my future.
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