| Jules51 | -- 01-03-2024 @ 6:33 AM |
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Struggling with a tune-up on my 51: (car was driven before process started) * New plugs are Auto-lite 216; gapped at 0.030 * Idle set at 500rpm * Timing is right on the mark with vacuum disconnected * Idle mixture screw at 0.75 turns * Points are gapped 0.015 Test drove, ran very smooth; no hesitation, good response and power. Now, my issues: pulled plugs - heavy black carbon Is this too lean or too rich???? Thanks Jules51
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| 40cpe | -- 01-03-2024 @ 8:09 AM |
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If your test drive was out on an open road with car up to operating temperature, your mixture is rich. Check the power valve in the carburetor. If it is blown you will have a rich mixture.
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| carcrazy | -- 01-03-2024 @ 8:27 AM |
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This is too rich. Look at the carburetor main metering jets (MMJs) and go one or two sizes smaller. For example if the current MMJs are o.o51, marked as 51 go down one size to MMJs marked 50. If there are wet deposits on the plugs, the engine may be burning oil which is getting past the rings and/or the valves. Using a vacuum gauge, check the manifold vacuum at idle. You can check it at the port on the intake manifold below the carburetor that provides the vacuum source for the windshield wipers. A healthy engine will indicate about 19" of vacuum at sea level. Check the compression in each of the cylinders while cranking the engine with the ignition off. Acceptable readings would be 80 PSI or greater with all cylinders within 5 to 10 PSI of each other. Look inside of the tailpipe(s) for oil/carbon deposits. Do you notice blue smoke coming from the tailpipes while the engine is running? If so, the engine is burning oil at a rate of 1 Qt/100 miles or so. For a used Flathead, an acceptable rate of oil consumption is 1 Qt of oil burned per 300 or more miles. At his rate the engine should not show any visible blue smoke while running. This message was edited by carcrazy on 1-3-24 @ 9:42 AM
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| Jules51 | -- 01-03-2024 @ 2:40 PM |
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Thanks for the feedback. Thanks Jules51
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| NGABronco | -- 01-06-2024 @ 5:23 PM |
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How did the plugs you took out look???
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| 51woodie | -- 01-07-2024 @ 5:03 PM |
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To add to carcrazy’s suggestions, make sure you have the throttle wide open when doing the compression tests. Also, when Charlie New York rebuilt the carb for my 46 Coupe 59 AB, he found that a prior owner had drilled the main jets to oversize them, so the number on the jets was misleading, and the reason I had poor mileage and carbon fouled plugs. Just another possibility. This message was edited by 51woodie on 1-7-24 @ 5:16 PM
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