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09-13-2013, 07:39 AM | #1 |
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Downdraft Carb suggestions
I want to put a downdraft carburator on my stock model a engine. Which one should I look for? 81,97 or 94, and what is the best way to set it up?
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09-13-2013, 07:56 AM | #2 |
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Re: Downdraft Carb suggestions
a weber ! best by far .......
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09-13-2013, 08:01 AM | #3 | |
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Re: Downdraft Carb suggestions
Quote:
Just out of curiosity, have you considered installing a Model-B carburetor & manifold for a little more airflow? With those, there is not a need for plumbing in a fuel pump when used on a Model-A. . |
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09-13-2013, 08:37 AM | #4 |
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Re: Downdraft Carb suggestions
Is there a quick way to ID the B manifold? Headed to a swap meet today.
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09-13-2013, 08:48 AM | #5 | |
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Re: Downdraft Carb suggestions
Quote:
tk
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anyone need some Model A restoration work done in Illinois? shoot me an email for pics and information [email protected] |
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09-13-2013, 11:31 AM | #6 | |
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Re: Downdraft Carb suggestions
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Quote:
Charlie Stephens |
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09-13-2013, 05:05 PM | #7 | |
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Re: Downdraft Carb suggestions
Quote:
Charlie Stephens |
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09-13-2013, 06:48 PM | #8 |
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Re: Downdraft Carb suggestions
I have a new English 97 on a heated Charley Yapp manifold. It runs noticeably smoother than the Zenith. Used an air/fuel meter to check jetting. smaller jets were too lean,stock jetting was just right.
It is a little touchy to start hot. I think I will try a heat insulator betweeen carb and manifold. Air filter in pic is too restrictive. A 4" tall K&N works good. |
09-15-2013, 03:26 AM | #9 | |
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Re: Downdraft Carb suggestions
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A phenolic spacer twixt carb and manifold fixed it As you say, stock jets have worked for me. |
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09-17-2013, 12:10 PM | #10 |
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Re: Downdraft Carb suggestions
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09-13-2013, 08:53 AM | #11 |
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Re: Downdraft Carb suggestions
I use a 97 just because its the best carb I had around. It does run a little rich but its not too bad. Still gets about 20 miles per gallon.
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09-13-2013, 09:35 AM | #12 |
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Re: Downdraft Carb suggestions
I have found the opposite of what Brent says. The 81 is adequate, and better than the stock carb, but the 97 is better, and cheaper. They usually need to be totally stock but sometimes may need a slight main jet change. I've tried them all.
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09-13-2013, 11:30 AM | #13 | |
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Re: Downdraft Carb suggestions
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Ohh come on now Jim, when have you EVER had a stock engine?? |
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09-13-2013, 10:12 AM | #14 |
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Re: Downdraft Carb suggestions
I have a Weber on mine, and it works great. Can't compare it to any other DD, just haven't used them.
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09-13-2013, 10:15 AM | #15 |
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Re: Downdraft Carb suggestions
Stromberg 48,81,97 all run good on an A block. Of course you have to jet it correctly, but that's not hard to do. On a flat head you want the mixture to be a little rich, rather than lean. Lean will burn up a motor. People often refer to the 94 as a stromberg, but it's actually a Holley. It's he cheapest one out of all of them, but they tend to run leaner than a stromberg. I have a 48 and I love it, I had an 81 once and traded it for a weber and boy was that a mistake. The webers are fine, but the strombergs give you faster acceleration in my opinion and run better down the highway. The webers do get better gas mileage though. But not by much. I've tried most of the popular downdraft conversions, and the stromberg has been my favorite so far. You can usually pick up a 48 or a 97 in decent condition at a swap meet for about 75-100 dollars that needs rebuilding. For an 81 you can expect to give 250-300 for one that needs rebuilding, or closer to 400-500 for a rebuilt, if you can even find an 81. They reproduce the intake manifolds, and I think they're right around $200 for the manifold.
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09-13-2013, 10:16 AM | #16 |
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Re: Downdraft Carb suggestions
I run dual updraft with B carbs. Its easy, bolt them on and thats it. I use original numbered jets. Gravity flow works fine, no pump or pressure regulator needed. This setup will run good, even on a completely stock engine. For best results with any mods on the model A, a higher compression head should first be added to really feel the improvement.
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09-13-2013, 11:05 AM | #17 | |
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Re: Downdraft Carb suggestions
Quote:
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09-13-2013, 12:55 PM | #18 |
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Re: Downdraft Carb suggestions
Here is a view of the setup on the speedster. The manifold is a cast iron uniflow that was made in the thirties. This manifold has larger runners and performs real good. I got this manifold from Berts, several years ago.
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09-13-2013, 11:58 AM | #19 |
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Re: Downdraft Carb suggestions
The B manifold is also "clocked" a few degrees toward the motor. How do you overcome this in an A and hook up the GAV?
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09-13-2013, 12:26 PM | #20 |
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Re: Downdraft Carb suggestions
Snyders has a kit to solve this problem. Look on page A-136. Part number A-9510-K Lists for $31.00 . Its kinda pricey for what it actually is. I cut the mounting flange off the manifold, rotated it as needed and brazed it back on. Be careful if you try this. The brazing job has to be good or you will end up with vacume leaks.
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