| Johns46coupe | -- 09-28-2010 @ 11:50 PM |
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I just replaced a Cleveland Groves carb on my 46 with a rebuilt Holley 59 from Little Dearborn. It used to idle smoothly at about 500 RPM and had plenty of power but poor gas mileage and sooty plugs. Now with the Holley, the RPM's vary greatly and it's popping out the dual pipes as it sits in my driveway. I can keep it running only with the idle RPM set pretty high. If I go to lower RPM, it slows down, speeds up, and repeats the cycle over and over until it stalls. I've tried setting the fuel/air mixture with a vacuum gauge but I can't get it to run smoothly or slowly enough to really set. Previously, with the old carb, the vacuum was 18 to 20 at idle. It's drivable this way with the RPM's set high but lacks power. The ONLY other thing changed is a new clutch, pressure plate, etc which, knock on wood, seem to function just fine. Any direction you can point me in? As always, thanks for your ideas! John
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| supereal | -- 09-29-2010 @ 9:54 AM |
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I suspect a vacuum leak, either on or near the carb or the intake manifold. You can pin down the problem by re-installing the old carb to see if the problem goes away. Most of the time, the last thing you did causes the present problem. Typical vacuum leaks occur from bad gaskets and warped carb bodies, cracked or loose vacuum hoses, such as those to the wipers or distributor, and sloppy throttle plate shaft bushings. Be sure the float level is properly set. Anything that causes an engine to "lope" at idle will smoke the plugs.
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| TomO | -- 09-30-2010 @ 10:12 AM |
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It sounds like the idle mixture is too rich. Turn in the mixture screws until the engine dies, then back out 1/2 turn. Your idle should even out at about 450-500 rpm. If it does not, you probably have an internal leak in the carburetor. Tom
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| Johns46coupe | -- 09-30-2010 @ 1:29 PM |
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Thank you gentlemen. There was a speck of dirt between the fitting of the distributor vacuum line at the intake manifold and the mixture was rich. Adjusted the mixture with a vacuum gauge and now have a steady 21 at about 525 RPM. As always, I appreciate your thoughts and this forum. John
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