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Old 02-06-2017, 11:29 PM   #1
alvisoroadsters
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Default Model A Engine and Dual Carbs

Hi All, I've searched the archives but never really found what I was looking for. I've asked on the HAMB, but I've always had great experience here on the Barn, so I thought it might help as well...

I have a stock Model A engine and a Burns twin carb intake. I've heard Stromberg 81's are the ideal carb set for this engine, due to the fact they flow at 125 CFM.

I have a pair of Holley 94's, and have also been looking at Stromberg 97's due to their availability as well.

Questions for the community...
1) Would the twin Holley 94 carbs be "too much carb" for this application, or can you toy with the jetting to make it work?

2) With the Strombergs, the 81's flow at 125 CFM and the 97's flow at 150 CFM. Do you think the 97's would work, or the best bet being to snag a set of 81's?

If the Holley 94's or the Stromberg 97's would be fine, can anyone share their jetting success (and power valve selection for the 94's)?

I'm getting ready to tear into the Model A and just want to make sure the selection isn't too much for the engine and it's enjoyable in the end.

Thanks in advance!
Jake
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Old 02-07-2017, 12:25 AM   #2
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Default Re: Model A Engine and Dual Carbs

What other equipment, and what is the intended use?
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Old 02-07-2017, 12:33 AM   #3
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Default Re: Model A Engine and Dual Carbs

Right now it is stock but have a mess of incremental upgrades planned, such as better gearing and engine upgrades.

Goal is to have it run a consistent 50 to 60 mph, so I can drive on highways without concern. Not freeways or anything that fast, but there's a lot of 55 MPH roads around me I need to keep up on.
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Old 02-07-2017, 04:44 AM   #4
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Default Re: Model A Engine and Dual Carbs

Been running twin 97's for six years and 15k miles.
Contact me via email, be glad to pass on tips.

Ken
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Old 02-07-2017, 07:41 AM   #5
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Default Re: Model A Engine and Dual Carbs

I've always heard the 81's are the way to go-that the larger are overkill-but I would have to assume it is all in the setup.
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Old 02-07-2017, 09:11 AM   #6
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Default Re: Model A Engine and Dual Carbs

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I have a burns dual intake and run 2 81's. I also have a Brumfield 6:1 head, stipe cam and all of this in a Model B engine. I'm also running a mechanical fuel pump. I have had excellent results with main jets of .036, idle jets of .028, and a #71 power valve. I was told that 97's would be too much carburetor, but there are certainly those here on the Barn that are doing just a well. Couldn't be happier...

Frank
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Old 02-07-2017, 09:24 AM   #7
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Default Re: Model A Engine and Dual Carbs

I ran 2 updraft tillotsons with large intake valves , a reground touring cam(?) and a 5.9 head. It had plenty of power for the hills but this does not increase the touring speed. That requires gearing and there are plenty of posts on which way to go with rear end gears, overdrives, 4 speed transmissions and the like. They do require a strong engine, but my personal opinion is it does not require the dual carbs that you are thinking about and they are a pain in the neck to sync. Jack
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Old 02-07-2017, 10:20 AM   #8
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Default Re: Model A Engine and Dual Carbs

I've used a single 97, two 97's, Mooneyes EFI and found the optimum setup for me is the Weber 32/36. I have all of the good stuff on my engine and like others here, recommend making drive train improvements first. Painting the engine red is certainly a cheap way to add power
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Old 02-07-2017, 10:27 AM   #9
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Default Re: Model A Engine and Dual Carbs

denis4x4. You're right.! We had Massey Ferguson tractors on the farm. It is a little known fact that if you paint a green tractor red, you will gain at least 5 more hp.
This is known as farmboy rivalry. Lol. Jeff
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Old 02-07-2017, 10:47 AM   #10
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Default Re: Model A Engine and Dual Carbs

I use a single 97 Stromberg, was told by vendors that two 97s were overkill, and not necessary for the Model A.
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Old 02-07-2017, 11:23 AM   #11
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Default Re: Model A Engine and Dual Carbs

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Originally Posted by JDupuis View Post
denis4x4. You're right.! We had Massey Ferguson tractors on the farm. It is a little known fact that if you paint a green tractor red, you will gain at least 5 more hp.
This is known as farmboy rivalry. Lol. Jeff
Yep, gotta be RED, or it stays in the shed.

Farmall rules.
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Old 02-07-2017, 11:32 AM   #12
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Default Re: Model A Engine and Dual Carbs

Some think running DUALS require MUCH smaller jets. That's NOT the case, remember that EACH carb is drawing only 1/2 as much air, as a single system. HALF as much air, equals 1/2 as much FUEL, delivered!
Bill Cypher
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Old 02-07-2017, 11:49 AM   #13
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Default Re: Model A Engine and Dual Carbs

Plenty of carb CFM calculators out there. Here's one...

http://www.4secondsflat.com/Carb_CFM_Calculator.html

They compute that a 200 CID Model A at 3,000 RPM needs about 150 CFM. If you try to supply much more than that you could have some drivability issues.

Dual carbs are pretty cool, however , and I would personally try to make them work. Use the smallest CFM carbs that fit the manifold, longer duration/higher lift cam, higher compression, play with jet sizes.

Good luck!
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Old 02-07-2017, 11:51 AM   #14
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Default Re: Model A Engine and Dual Carbs

Quote:
Originally Posted by denis4x4 View Post
Painting the engine red is certainly a cheap way to add power
Can you give me the paint code you used?
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Old 02-07-2017, 11:58 AM   #15
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Default Re: Model A Engine and Dual Carbs

You do not need the bigger Holley or Stroms for your intended use. The Strom 81,and the Holley Model 92( the 81 venturi size replacement for the Stom 81) give better gas mileage. If you use dual Holleys, use the 3.5 or 4.5 power valves. Be careful they do not leak on installation. Stock size jets are fine as Bill W says.
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Old 02-07-2017, 12:18 PM   #16
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Default Re: Model A Engine and Dual Carbs

Quote:
Originally Posted by denis4x4 View Post
I've used a single 97, two 97's, Mooneyes EFI and found the optimum setup for me is the Weber 32/36. I have all of the good stuff on my engine and like others here, recommend making drive train improvements first. Painting the engine red is certainly a cheap way to add power
Denis4x4
What jets are you running, mine seems to be a little lean at full throttle.
Thanks
Dick
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Old 02-07-2017, 01:06 PM   #17
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Default Re: Model A Engine and Dual Carbs

To EMF...what ever red engine paint they sell at O'Rielly's
To bettlesr...I live at 6703' elevation and running .36 jets. I suspect that you need info from people living at sea level.
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Old 02-07-2017, 02:03 PM   #18
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Default Re: Model A Engine and Dual Carbs

Denis4x4
Thanks. I guess I should hook up my Innovate Air/Fuel gauge that's been sitting in its box for years now and see what is really happening.
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Old 02-07-2017, 02:17 PM   #19
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Default Re: Model A Engine and Dual Carbs

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Originally Posted by Tom Wesenberg View Post
Yep, gotta be RED, or it stays in the shed.

Farmall rules.
But Green is mean.
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Old 02-07-2017, 02:20 PM   #20
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But Green is mean.
Oliver Green, that is!
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