| Tracker | -- 05-20-2014 @ 4:03 PM |
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My 1951 Mercury has suddenly started running rich..it does not emit black smoke that I can see but it fills up the garage with noxious fumes almost upon starting.It has a completely stock original engine with a two bbl Holley which adjusts easily between settings but the problem persist regardless of adjustments to the air screws. I bought a carb kit from Birdhaven but I'm not clear on what I should be looking for to repair. Any thoughts or suggestions on this would be appreciated. Thanks & regards Tracker
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| TomO | -- 05-21-2014 @ 7:26 AM |
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Tracker, before tearing apart your carburetor, check the spark plugs for color. If they are black and sooty, you are running rich or have been driving slow speeds and doing a lot of idling. The idle mixture screws are just that. They adjust the mixture for the idle when the engine is at operating temperatures. They do not have an effect when the engine is cold or at driving speeds. Your automatic choke may be the culprit also. It should be closed when the engine is cold and not running, open about 30 degrees when the engine is started and open all of the way, when your temp gauge needle moves off of cold. You may be able to just adjust the automatic choke or replace the heat tube for it and then adjust it. Tom This message was edited by TomO on 5-21-14 @ 7:28 AM
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| supereal | -- 05-21-2014 @ 2:33 PM |
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I think TomO is on the right track. The "coincentric" carb is an odd and complcated unit. If you need a diagram, I can post it.
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| TomO | -- 05-22-2014 @ 7:25 AM |
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Tracker, Unless you have a lot of experience with carburetor repair, I suggest that you give up the idea of putting a kit in your 51 carburetor. As Supereal said, these are very complicated carburetors and do not take kindly to amateur repairs, sometimes going as far as to start on fire. These old cars do emit noxious fumes as part of their character. There are no computer controlled fuel injectors and spark timing to control combustion and they lack the catalytic converter that removes some of the more harmful results of combustion. Never run any car inside a garage without some way to carry the exhaust fume outside of the garage. An open garage door is not sufficient, the fumes must be carried far enough away so they cannot come back in. CO does not have an odor and makes up the majority of the fumes. The stuff that you can smell will not kill you, but it is combined with CO that can kill you. Tom
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| rotorwrench | -- 05-22-2014 @ 5:34 PM |
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There are several things to inspect that can cause over rich operation or just plain fuel leakage. The guys are correct about being careful with these carbs when maintaining them. Previous damage may have happened at the last rebuild that is now starting to affect the way things function now. These carbs are shrouded so it's hard to detect internal bowl leaks without disassembly. The bowl on top can get warped from previous maintenance and leak down onto the throttle body. The power valve vacuum circuit that runs up through the top of the shroud can have problems that don't allow the power valve to function correctly. If the float sticks or hangs up in the open position then the bowl will leak internally or vent at the back where it's hard to see. Lots of things that can happen including the choke adjustement or internal mechanism problems that have been mentioned. Either a Holley manual or the 49 thru 51 Lincoln Mercury Overhaul Manual are a must for instruction on cleaning & adjusting these old instruments. There are a lot of little parts that have to be accounted for and small differences between models so knowing what the ID markings mean and having good illustrated parts breakdowns will help more than I can describe. This message was edited by rotorwrench on 5-22-14 @ 5:38 PM
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| Tracker | -- 05-23-2014 @ 6:15 AM |
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Tom The plugs looked normal but I cleaned them anyway. The auto choke is frozen in the open position and has no practical effect. Very few cold days here to worry about so never gave it much attention. Sprayed WD -40 on the shaft exteriors and noticed a slight change in rpms. Thanks for your response as always. Tracker
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| Tracker | -- 05-23-2014 @ 6:17 AM |
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Thanks SR...I have a 49-1951 Merc shop manual which has a section on the Holley carb but its way above my level of expertise. Thanks as always for your response.
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| Tracker | -- 05-23-2014 @ 6:26 AM |
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Thanks RW...one thing is for certain. I will ask before investing in carb rebuild kits in future. I have located a couple of pro carb rebuilders on the net but there services are pretty high priced. I think I could probably buy a NOS Holley for the prices they charge to do an old Holley like mine but I may not have any choice. This thing really stinks now when idling but surprisingly still runs very smooth and idles well. I appreciate your response and have about decided this is not something I can do with my limited expertise in such things. Tracker
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| Tracker | -- 05-23-2014 @ 6:33 AM |
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Tom I have zero experience rebuilding a carb and I know that some are far simpler than others. The Holley unfortunately does not appear to be one of them. I don't idle the car in the garage any longer than it takes to start it and roll it outside. It still stinks up the garage and smells like old varnished fuel ( like my old lawnmowers used to meal at summers end ) and what it does to your clothes in that short a time period is disgusting. Unless I can locate a NOS Holley Carb, guess I am going the way of hiring a pro builder and biting the bullet on cost. Thanks again as always for your help & guidance. Tracker
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| TomO | -- 05-23-2014 @ 8:19 AM |
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Tracker, If your plugs look normal, and the car runs well, then I seriously doubt that rebuilding or replacing the carburetor will solve your problem, and may introduce a new problem. You said the fumes smell like bad gas. My guess is that it is probably bad gas. The newer formulas for gasoline are not very stable and can go bad in as little as a couple of months. You can add some Seafoam to the tank and drive it to burn off the bad gas or, drain the tank and start over with fresh gas. I don't know what you would do with the drained gas. I have never tried to dispose of old fuel. I normally do not recommend additives to either the gas or the oil, but Seafoam has helped me several times when I have been sold bad gas. It also helps to burn off the H2O that accumulates from the Ethanol separating from the gas. If you decide to rebuild the carburetor, Daytona Carburetor has the best reputation for the Holley Teapots. They are not cheap, but you will get a quality job. If your choke is frozen inside the housing, you will have to remove it from engine to disassemble and clean it properly. You may also have a problem with the heat tube allowing exhaust gases to enter the choke housing and corroding the parts. Tom
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| Tracker | -- 05-24-2014 @ 4:54 AM |
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Tom Thanks for the lead on Daytona Carb......if the Seafoam idea does not do the job, I will probably use this firm for the re-build. Again, many thanks to you and all others on this site who responded to my request for help. This is still the best user friendly site on the web and has the most knowledgeable advisors to be found.
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| TomO | -- 05-24-2014 @ 7:05 AM |
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Tracker, You are welcome. and thanks for the compliment. I have to agree that this is the best site to come to for advice, everyone on here tries to be nice and show respect for anyone that posts a question or reply. Tom
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