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Posted By Discussion Topic: Carburetor Adjustment -- page: 1 2     39Fordfan 10-30-2009 @ 12:35 PM reply profile send p.m. New Member Posts: 191 Joined: Oct 2009 Hi there, I've got a '39 Fordor with a Model 91-99 carburetor. It seems to be running fairly rich. I put new NKG plugs in it this Spring and they are black and sooty now. Plus it seems to consume more fuel then it used too. My questions are: how do a adjust this Carb' properly? My '38-39 manual doesn't seem to address this. Also, I noticed a very small amount of gasoline seems to be seeping down the place where the carb' mounts to the intake. Do I need to rebuild it? Or something simpler? Thanks! 40 Coupe 10-30-2009 @ 1:08 PM reply profile send p.m. Senior Posts: 1674 Joined: Oct 2009 the 91-99 is the proper model for the 39 85HP the only adjustments are the float height and drop and the idle needle valve settings on the base. You may want to try a hotter plug to get rid of sooty deposits. The idle needles should be adjusted for highest and smoothest idle with the engine hot. Work between the two and the final adjustment should NOT be more that one turn out. ford38v8 10-30-2009 @ 4:44 PM reply profile send p.m. Senior Posts: 2758 Joined: Oct 2009 39 Fan, 40 Coupe gave you the straight skinny, but I'll take it a step further: Your description of the problem leads me to believe that your Power Valve is leaking. This is common these days, as the new gasoline attacks the rubber diaphragms. Remove the carb body from the black cast iron base, and you'll find the Power Valve on the bottom. After removal of the valve, check the diaphragm by sucking on the unit. It should hold a suction to your tongue if it's good. It's a one-way valve, so try it the other way if it fails. Two strikes and it's out. Replacement is easy, but you must obtain one without the radius on the base of the threads, or the gasket won't seal. a valve having the radius will seal if you use a common garden hose gasket, as those are thicker. there's a place in Florida that sells valves without the radius: Daytona Parts Company http://www.daytonaparts.com/ They also do restoration of the zinc colored carb bodies, as original, but the online pictures don't show the color we need. If you go this route, be sure you make it clear what you need. The website sucks, as far as I'm concerned. Alan 39Fordfan 10-30-2009 @ 6:04 PM reply profile send p.m. New Member Posts: 191 Joined: Oct 2009 Thank-you for you replies, Yes, I put the hotter NKG plugs in and they're still just as sooty as the old Champions were. What's the optimal gap for these plugs? Maybe I didn't gap them correctly. So bear with me on the carb' adjustment. Are you saying that this adjustment is totally by ear and feel? Work the two spring adjusted screws facing the firewall for best & smoothest idle? That's it? Thanks! Alan thank-you for the detailed Power Valve info. I already had to replace the fuel pump for the same reason. The fuel pump diaphragm cut loose and started leaking because of the corn in gasoline. Do you think the Power Valve diaphragm might also be a contributor to it running rich? Is there anything else I should look out for when pulling it off or putting it back together? Thanks! ford38v8 10-30-2009 @ 10:14 PM reply profile send p.m. Senior Posts: 2758 Joined: Oct 2009 Fan, The Power Valve is likely the reason you are running rich. Get that problem taken care of and you won't have sooty plugs. Be sure to get your gaskets to seal properly, that's as important as a good power valve. Don't remove the air horn just yet, see if the valve replacement takes care of the problem first. One thing at a time. Alan 51f1 10-31-2009 @ 3:14 AM reply profile send p.m. Senior Posts: 573 Joined: Oct 2009 If you want to be more scientific with your carb adjustment, use a vacuum gauge. Just connect it to the windshield wiper connection and adjust the idle screws for the maximum vacuum The results won't be any better than doing it by feel. Richard 40 Coupe 10-31-2009 @ 7:43 AM reply profile send p.m. Senior Posts: 1674 Joined: Oct 2009 yes the carb idle adjustment is very simple, and the carb and engine should react to the adjustments so that you can here and see the engine run smoother and engine RPM increase slightly, or if you screw the needles in too far the engine will run rough. You can also use a vacuum gauge to see the vacuum increasing. If this does not happen or the final adjustment is too far out (1+ ) then I would suspect the power valve. Usually if the power valve is leaking the engine will take a long time to restart and will flood while sitting with the fuel from the carb draining into the engine with the engine off. If replacing the power valve do be careful to observe the warnings posted by others regarding the inability of some valves to seat properly and have the correct gasket seal properly. 40 Coupe 10-31-2009 @ 7:44 AM reply profile send p.m. Senior Posts: 1674 Joined: Oct 2009 gap plugs at 0.028 39Fordfan 10-31-2009 @ 9:08 AM reply profile send p.m. New Member Posts: 191 Joined: Oct 2009 Thanks for the great information 40coupe, Richard & Alan. That should keep me going for a while. A couple more things for you... Alan said he thought the Daytonaparts website sucked. It seems like a good place to go when you are ready for a carb' overhaul. Would you recommend them? Or maybe somebody else? I'm a relative Newbie, so at what point do I decide to just rebuild it myself versus sending it out? I also wasn't clear on what Alan meant when he said Daytonaparts do restoration of the zinc colored carb bodies, as original, but they don't show the color we need. Could you clarify that a little for me? Which color do we need? Is that what you meant? Thanks! supereal 10-31-2009 @ 9:15 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Are you adding anything to your gas such as MMO? Too much, or any, in some cases, will produce sooty plugs. Is the operating temperature reaching somewhere in the vicinity of 180? We often hear of overheating, but running cold, particularly at this time of the year, can result in incomplete combustion. As for leakage, before you disassemble the carb, remove it from the manifold and set it overnight on the bench to see if it is actually losing gas somewhere, such as the power valve. Once you start to take things apart, it is likely you will not find the cause of the problem.

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