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Old 11-03-2014, 06:08 PM   #1
Bob Johnson
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Default Model B Carburetor rebuild

I am rebuilding two Model B carburetors. I ordered two rebuild kits. They are labeled 00511-1 Sacramento Vintage Ford. I flow tested the jets and the results were not what I thought they should have been. I used a 37 1/4" head.

For the Idle jets I recorded 58 and 60.
For the Main jets I recorded 80 for one and 83 for the other.
For the Cap Jet I got 378 and 376.
For the Comp jet I got 148 and 142.
For the Power jet I got 46 and 44.

The Main and Power jets are way off. I know how to adjust the jets by drilling. My questions are ---> Has anyone else measured the flow rates for the jets in the 00511-1 B cab rebuild kit? If so what flow rates did you measure and did you open up the jets? Or has anyone rebuilt a B carb with this kit without adjusting the jets? If so did the engine run lean with not enough power?


Below is a table from Vince Falter's "Ford Garage" showing flow rates from various sources.


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Old 11-04-2014, 03:33 AM   #2
H. L. Chauvin
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Default Re: Model B Carburetor rebuild

Hi Bob,

Thanks for taking the time to report on these helpful comparisons between "new" jet flow & the recommended & specified jet flow rates.

Appears the B "new" jet flow readings you are getting are just as far off as the A "new" flow readings I got about 8 years ago when testing same.

I did not keep records because the "new" jets from several responsible vendors were really ridiculous & a were a waste of money spent. When called to report the findings the vendors replied these were the best they could find to offer.

All varied quite a bit & I am sure they were poorly manufactured with absolutely no quality control.

I had several old "original" jets from several carburetors that were correct so I re-installed these "original" jets.

Under "Search", one can find out where it has been reported to buy quality flow tested jets.
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Old 11-04-2014, 11:07 AM   #3
Bob Johnson
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Default Re: Model B Carburetor rebuild

I measured the main jet hole size and it was about 0.029". I measured an original main jet and the hole was 0.037". These hole sizes account for the difference in flow rates. Below is a picture of the reproduction and original main jet holes. Notice the size of the holes and the shape of the jet around the hole. On the original there is a concave area around the hole. Again has anyone else rebuilt a B carb? If so what did you find in quality of the parts and performance of the rebuilt carburetor?

Bob

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Old 11-04-2014, 09:31 PM   #4
SAJ
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Default Re: Model B Carburetor rebuild

Hi Bob, I rebuilt a B carb and the new jets were all over the place. I soldered and reamed various jets to the flows required (3-sided tapered reamers made by hand taper-grinding piano wire of suitable sizes). I indented the tips as on orig. jets to avoid capillary flow leaks. The flow rates I chose run the plugs very white, so I have the GAV 1/2 turn open rather than closed as proper on the B. This gives a slight tan tinge to the plug insulators and valve heads, which seems safer since I had burnt two exhaust valves previously on an A carb on the same engine. I have an exhaust gas thermocouple right next to no. 3 exhaust valve to keep an eye on temperature. As posted recently here, I see no difference in temp on the meter as I vary the GAV, but big changes when I retard the engine.
I get 21 to 23 MPG on a trip (Mitchell O/D) and 17 to 18 mpg round town on short trips.
These are big Imperial gallons (divide by 1.201 to get US MPG). One day I may recalibrate the jets so the GAV will run closed but there are lots of other things to do first.
I also have lots of new A carb jets that are wrongly sized too.
SAJ in NZ
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