The Ford Barn

Wedgetail · 07-02-2023, 10:18 PM

I put in new spark plugs recently (1940 Deluxe), and within 10 miles they were all black and sooty. Presumably the engine is running rich. I rebuilt the carburetor, and found that it looked like it had been rebuilt recently and all the gaskets looked new, just like the new ones I bought. If I pump the throttle with the engine off, a little gas leaks out of the throttle plate axle (no seal there). If I clean off a spark plug, it gets black and sooty in a couple of minutes. Is this a problem? What else can I do?

SoCalCoupe · 07-02-2023, 11:27 PM

Spark plug reading is tricky. "it gets black and sooty in a couple of minutes." If that means the engine is cold and just idling, it doesn't mean anything. Or even just idling, may not mean much.

petehoovie · 07-03-2023, 12:59 AM

Terry,OH · 07-03-2023, 07:36 AM

If your driving your car and find the plugs to be covered with soot as #7 above photo or even worse. The problem is most likely the Carb. or it's adjustment. The 40 Ford has a Ford or Holley 94 Carb model 91-99. Before disassembly adjust the idle mixture needles for the highest vacuum and smoothest idle and see how the car and plugs respond. If you disassemble it should have .050" main jets. It is possible the fuel level is too high, or the power valve or it's gasket are leaking. Daytona is about the only place to get a rebuild kit with the proper replacement parts but I would still keep the inlet valve and it's steel needle.

rustedorrotting · 07-05-2023, 11:14 AM

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If it had been rebuilt lately, the problem is most likely the power valve. The ones available today have a radius next to where the seal sets which wont allow it to seal. pull the carb and the valve and look at the sealing surface. www.charliesspeed.com buys these valves in bulk and machines the radius off. If I can be of any more help, let me know. I have recently been rebuilding/restorring these old carbs.

07-02-2023, 10:18 PM	#1
Wedgetail Junior Member Join Date: Dec 2021 Location: Cambridge, MA Posts: 29	Black spark plugs I put in new spark plugs recently (1940 Deluxe), and within 10 miles they were all black and sooty. Presumably the engine is running rich. I rebuilt the carburetor, and found that it looked like it had been rebuilt recently and all the gaskets looked new, just like the new ones I bought. If I pump the throttle with the engine off, a little gas leaks out of the throttle plate axle (no seal there). If I clean off a spark plug, it gets black and sooty in a couple of minutes. Is this a problem? What else can I do?

07-02-2023, 11:27 PM	#2
SoCalCoupe Senior Member Join Date: Sep 2021 Location: Point Loma, San Diego, CA Posts: 431	Re: Black spark plugs Spark plug reading is tricky. "it gets black and sooty in a couple of minutes." If that means the engine is cold and just idling, it doesn't mean anything. Or even just idling, may not mean much.

07-03-2023, 12:59 AM	#3
petehoovie Senior Member Join Date: May 2015 Posts: 8,550	Re: Black spark plugs __________________ The only thing nice about being imperfect is the joy it brings to others.... *"Silver rings, your butt! Them's washers!"* "We shot our way out of that town for a dollar's worth of steel holes!" - from 'The Wild Bunch' - 1969 https://www.youtube.com/watch?v=7NReUd2_0u0

07-03-2023, 07:36 AM	#4
Terry,OH Senior Member Join Date: May 2010 Posts: 4,799	Re: Black spark plugs If your driving your car and find the plugs to be covered with soot as #7 above photo or even worse. The problem is most likely the Carb. or it's adjustment. The 40 Ford has a Ford or Holley 94 Carb model 91-99. Before disassembly adjust the idle mixture needles for the highest vacuum and smoothest idle and see how the car and plugs respond. If you disassemble it should have .050" main jets. It is possible the fuel level is too high, or the power valve or it's gasket are leaking. Daytona is about the only place to get a rebuild kit with the proper replacement parts but I would still keep the inlet valve and it's steel needle.

07-05-2023, 11:14 AM	#5
rustedorrotting Member Join Date: Feb 2015 Location: Northwest lower Michi9gan Posts: 45	Re: Black spark plugs Sponsored Links (Register now to hide all advertisements) If it had been rebuilt lately, the problem is most likely the power valve. The ones available today have a radius next to where the seal sets which wont allow it to seal. pull the carb and the valve and look at the sealing surface. www.charliesspeed.com buys these valves in bulk and machines the radius off. If I can be of any more help, let me know. I have recently been rebuilding/restorring these old carbs.