The Ford Barn

Sid · 02-25-2026, 05:12 PM

I have a 49 F1 with a stock flat .100 over and Edelbrock heads. stock cam. I have 2 deuce on it now but only running on 1 carb. I am going to get the other carb functioning. Running Holley 94's. I was wondering what jets and what power valves most found that work? Do you set both carbs. the same jetting and power valves? I am 2300 feet elevation.

Ziggster · 02-26-2026, 06:53 AM

I assume you’re going to go with direct/straight linkage. I just ordered some #48 and #49 jets and 5.5 psi PVs for my 2 x 2 direct/straight setup from Vintage Speed. I’m also going to try a progressive linkage. For that setup, went with #51 jets and a 5.5 psi PV for the primary. For the secondary, went with #48 jets, and a plugged PV for the secondary. I’m using a vintage Edmunds 2x2 intake which allows for the stk generator mounting. Charlie from Vintage Speed recommended the stuff for the progressive setup, and I just Googled the stuff for the direct/straight setup. Will know in a couple months how each works once the snow melts and I can get my speedster back
Outside.

drfromnc · 02-26-2026, 08:31 AM

Im running #43 jets and 67 Pv on my dual 97s atop slingshot intake, Edelbrock heads, .125 over 59a, kiwil100 cam, straight/direct linkage. My elevation is about 150 ft. Engine runs like a scalded dog.

Sid · 02-26-2026, 03:46 PM

Quote:

Originally Posted by Ziggster

I assume you’re going to go with direct/straight linkage. I just ordered some #48 and #49 jets and 5.5 psi PVs for my 2 x 2 direct/straight setup from Vintage Speed. I’m also going to try a progressive linkage. For that setup, went with #51 jets and a 5.5 psi PV for the primary. For the secondary, went with #48 jets, and a plugged PV for the secondary. I’m using a vintage Edmunds 2x2 intake which allows for the stk generator mounting. Charlie from Vintage Speed recommended the stuff for the progressive setup, and I just Googled the stuff for the direct/straight setup. Will know in a couple months how each works once the snow melts and I can get my speedster back
Outside.

I am running Strombergs 97's on my 40 direct. Runs great that way. My little truck I have Holley 94's on but the front carb is non functioning. I am planning on running direct linkage on it. It is also a Edmunds intake. Since I am going to run direct linkage I was thinking maybe .49 jets in both carbs and maybe 5.5 and a 3.5 P.V. or a 5.5 and a 4.5 possibly. As I stated in my original post I am about 2300 feet ele. I appreciate any other opinions as well.

Mart · 02-26-2026, 04:21 PM

I run twin 94s on an 8ba manifold. This is on a 239 59A in my 33 coupe. I have stock jets which are 50s or 51s. I run stock power valves too.

It runs great.

I would suggest you try stock first and then try something else if it doesn't work.

The thing is, 94s will run rich for many reasons. Running rich for any one of these reasons will make you try leaner jets and try and compensate. But that's wrong. You need to find why it is running rich.

Float height. Leaking needle valve. Fuel pressure too high. Punctured float. Ruptured power valve. Wrong power valve seat shape. Wrong power valve gasket. Cracked power valve body. Warped lower and middle body castings.

I have made videos showing machining the castings to ensure a good seal around the power valve vacuum chamber. A leak here will stop the power valve from closing and give an over rich mixture.

When I did my dual conversion I first ran each carb on a single intake and made sure they both ran perfectly. Only then did I try them as a pair.

I hope this advice is some use to you.

There is a link to a 94 teardown and reassembly video here: https://www.fordbarn.com/forum/showthread.php?t=305182

Click the link in the first post

Mart.

Flathead Fever · 02-26-2026, 10:51 PM

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It can take a little defective work to get the correct carb jets dial in. I'd start with what people are recommending for your cubic inches and go from there. I was a smog tech for 30-years and basically worked on computer-controlled feedback carbs. But you can do the same A/F testing with an O2 sensor on non-computerized carbs, then you can really get it dialed in to see how rich or lean you are at. Most people never do this; they just pop the carbs on and they run them with whatever jets they have. They might be close enough to run that way, but they could be so much better dialed in. I would look up some vehicles on YouTube and see how the people tuned them using a 02 meter. It will cost you a little bit for the sensor and gauge, but you will be able to see exactly what your A/F ratio is at idle, driving and acceleration.

You also have to dial them in at idle, that is completely different than jetting the carbs. You want the idle A/F mixture screws turned out exactly the same amount, so both carbs are flowing exactly the same amount of fuel at idle, and both carbs' butterflies are opened up exactly the same amount. It's very important that both carbs are adjusted the same amount at idle. You can verify the idle mixture reading with your A/F mixture gauge. It can be done without the gauge but if you really want to be dead on correct and you don't have the experience of jetting carbs the A/F gauge will be a great help.

Here's a video. There are a bunch of them on YouTube, some better than others. You need a hole in the exhaust as close to the engine as possible for the sensor. I used to do this for a living then I had a stroke. Now I have a bunch of my own cars to do this to, just don't feel like it yet.

https://www.youtube.com/watch?v=D918ukEXXiU

Here is another one. This is big old Holley, but this shows you how little changes help dial the carb in and how the exhaust gauge helps you getting it correct. Lots of changes before it's finally dialed in.

Ziggster · 02-27-2026, 07:53 AM

Is there a way to “dial in” dual carbs using the A/F individually? Also, was cutouts to see if there was an “A/F app”, and sure if enough there is was, but the hardware/firmware is not cheap.

Flathead Fever · 02-27-2026, 08:39 PM

Is there a way to “dial in” dual carbs using the A/F individually? Also, was cutouts to see if there was an “A/F app”, and sure if enough there is was, but the hardware/firmware is not cheap.

As soon as you adjust the one carb it makes the second one out of adjustment. They have to be adjusted together. It really is easy to do it once you've practiced a bit. Be gentle with the screws, do not run them down into the seats hard, just barely until they touch and then back them out evenly for starters.

You want to disconnect the linkage from the carbs but make sure each carb has a throttle return spring while you are doing this. You want to adjust the idle speed, both throttle plate barely opened up. As soon as you adjust one A/F mixture you've changed the reading on the other carb. So, then you need to adjust the second carb but then you have changed the adjustment on the fist. You just need to go back and forth and back and forth until the idle is correct and both the carbs are finally adjusted evenly, same number of turns out on the A/F mixture screws. Then you need to adjust the idle speed, how far the throttle plates are open on both carbs at idle, they need the same amount opening at idle, it won't be very much. You can use a uni-sync to balance the carbs. All this does is verify the throttle plate are set the same at idle. Then you might have to adjust the idle mixture screws "again". You just keep going back and forth until the idle speed is correct, the a/f mixture is correct, and both carbs Idle mixture screws are turned out the same amount. It sounds confusing but it shouldn't take more than a few minutes to get them all dialed. Then when you have the carbs set you need to hook the linkage back up to them, without moving the idle plates by adjusting the linkage. Then make sure the carbs open all the way up with the gas pedal floored. This is all just to get it running, you might need to take it apart and jet the carbs and do it all again.

There's not much on YouTube. Here is a VW video on a uni-sync. All this is for making sure both carbs are open the same amount at idle. They were popular on VW's and foreign cars but come in handy on flatheads with multiple carbs.

ttps://www.youtube.com/watch?v=FDm7EtmfOlM

38 coupe · 02-28-2026, 06:54 AM

The question not asked: what distributor are you running? The stock distributor works very well with a stock single carburetor. As soon as you use dual carburetors you need a different ignition advance setup. You cannot connect your stock vacuum advance to manifold vacuum, that results in the reverse of the ignition curve you need.

Also, Innovate makes a clamp on O2 exhaust adapter that you can stick up the tail pipe and use without drilling a hole in your exhaust system. It works well as long as your exhaust system doesn't leak. I use one in a portable wide band setup I have so I can check carburetor adjustment without permanently adding an O2 gauge to a car. Search "Innovate O2 clamp on adapter" and you should find it offered by several different vendors.

john in illinois · 02-28-2026, 11:33 AM

You will be very close with stock jetting. John Lawson did dyno tests on 2 carb flatheads. His best runs were .046 main jets, .01 over stock for Stromberg 97s.
Stock 94 should be similar. The only time this is not true is with restrictive small
Air filters. They make it almost impossible to jet.

As mentioned you also need a different distributor for 94s.
John

Ziggster · 03-01-2026, 07:49 AM

Quote:

Originally Posted by 38 coupe

The question not asked: what distributor are you running? The stock distributor works very well with a stock single carburetor. As soon as you use dual carburetors you need a different ignition advance setup. You cannot connect your stock vacuum advance to manifold vacuum, that results in the reverse of the ignition curve you need.

Also, Innovate makes a clamp on O2 exhaust adapter that you can stick up the tail pipe and use without drilling a hole in your exhaust system. It works well as long as your exhaust system doesn't leak. I use one in a portable wide band setup I have so I can check carburetor adjustment without permanently adding an O2 gauge to a car. Search "Innovate O2 clamp on adapter" and you should find it offered by several different vendors.

I’ve never heard of this before. Could you please explain why?

glennpm · 03-01-2026, 10:06 AM

Quote:

Originally Posted by 38 coupe

The question not asked: what distributor are you running? The stock distributor works very well with a stock single carburetor. As soon as you use dual carburetors you need a different ignition advance setup. You cannot connect your stock vacuum advance to manifold vacuum, that results in the reverse of the ignition curve you need.

Good HAMB discussion

https://www.jalopyjournal.com/forum/...source.837581/

Ported vacuum diagrams and NOT manifold source

Bored&Stroked · 03-01-2026, 10:51 AM

A/F mixtures at idle are completely controlled by the two idle adjustment needles. Truth be told, I don't worry about A/F ratios at idle . . . I just adjust the idle mixtures and idle speed screws to get the engine to idle as I want it.

Also, the idle mixture screws have nothing to do with the main jets, power valves and off-idle A/F ratios.

Having an O2(A/F) meter is very valuable for main jet selection and even power-valve selection.

Power Valves: If you're running dual carbs, usually you will want to reduce the power-valve selection to a lower vacuum number.

Example: Maybe a stock single carb setup came with a #7 power valve and now (because of dual carbs) you may need to go to 5.5 power valves. The reason is that both carbs will see less vacuum and you don't want the stock power valves coming in too early (at a vacuum level of 7) and causing an over rich situation.

Having a properly installed O2 (A/F) meter will show you your A/F readings at different throttle/load conditions.

Distributor: As others mentioned, you should consider replacing your distributor with one that doesn't care about dual carbs. The stock "load-o-matic" distributor controls advance based on the specific vacuum signal of a single carb and stock engine - with a specific vacuum port off of that single carb (not the manifold). Your advance curve is probably way off, and you can't adjust it with the stock distributor.

I'd find either a good Mallory dual-point or better yet, get one of the converted SBC distributors from Charley NY. His converted SBC distributors will typically have a vacuum advance canister as well - which can help with fuel mileage (if you care about that). Having a distributor with the correct advance curve can make a heck of a difference in overall performance, engine temps, etc.

glennpm · 03-01-2026, 11:59 AM

Another good article IMHO

"Modifying the Holley 94 two barrel for late model distributors"

https://www.eatonbalancing.com/2010/...tors/#more-164

"The Holley 94 and 2100 two barrel carbs came as the standard equipment 2 barrel carbs on the 1938 thru 1956 Fords. When converting the distributors on the Y-Block Ford engines from the original Load-O-Matic (LOM) design to the later model Ford (1957 and up) distributors, the Holley 94’s original distributor vacuum port for the distributor will supply an excess of negative pressure or vacumm signal to the late model distributors. The original Holley 94/2100 carb port design uses an anti-spark valve as well as a speed sensing venturi port and a ported vacuum signal just above the throttle blades to provide the proper vacuum signal to the original LOM distributors. All three of these work in unison to supply a vacuum signal to the distributor even at full throttle with the LOM system. This is a good thing for a LOM distributor equipped vehicle but a bad thing for the later model distributors.

The LOM distributors did not incorporate a centrifugal advance and relied solely on the vacuum signal supplied by the carburetor in which to maintain the proper advance curve under a variety of driving conditions. When using these carbs with the later model distributor which incorporates both a centrifugal and vacuum advance system, hooking up the vacuum advance without any carb modifications will provide an excess of vacuum signal to the distributor’s vacuum advance chamber at both idle and full throttle. This in turn creates tuning and drivabilty issues as well as increasing the propensity for detonation. Here is a pictorial in which to convert the Holley 94’s and 2100’s so that only a ported vacuum signal is supplied to the distributor and in turn makes this older model carburetor function similar to the ’57 and up carbs in both performance and fuel economy."

69a · 03-01-2026, 04:14 PM

I have a 49 F1 with a stock flat .100 over and Edelbrock heads. stock cam. I have 2 deuce on it now but only running on 1 carb. I am going to get the other carb functioning. Running Holley 94's. I was wondering what jets and what power valves most found that work? Do you set both carbs. the same jetting and power valves? I am 2300 feet elevation.

The question has been asked, what distributor are you running.
You cannot use the original Fordomatic distributor if you are using multiple carburetors.
This is because the venturi vacuum is the only way the advance system works. It has no mechanical advance. If you are using 2 X 2 carburetors you have reduced the signal to the distributor by around 50%. There are several different solutions to this, but you need to let us know what distributor you have at the moment.

Sid · 03-01-2026, 07:49 PM

I do appreciate all the knowledge and input. I am running stock dist. I did the transformation. .050 jets in main carb. and .049 in the front. 6.5 power valve in the main carb. And now a 2.5 in the front tried plugging power valve but it wasn't happy so I had a 2.5 that I used. I did the linkage progressive so it opens up the front carb.at probably 1/3 throttle or so. I figured why be pushing excess gas while in town. I know it's not the way many of you would have did it but it seems to run very well. I drove it about 5 miles last night and pulled plugs today and they are a just shy of a dark cocoa. And the throttle is pretty responsive.

69a · 03-01-2026, 08:33 PM

[QUOTE=38 coupe;2439810]The question not asked: what distributor are you running? The stock distributor works very well with a stock single carburetor. As soon as you use dual carburetors you need a different ignition advance setup. You cannot connect your stock vacuum advance to manifold vacuum, that results in the reverse of the ignition curve you need.

You are NOT understanding the timing issue. The advance curve is now incorrect.
There are several solutions available. I'm using a small block Chev HEI that I converted myself. There are new "plug and play" electronic ones on the market. There is also one that Tubman recommends, but I'm not familiar with that one.

Sid · 03-01-2026, 09:04 PM

Yes I do understand. The motor runs nice as is. Yes I could put an HEI in And maybe it will be better. Maybe not. And I do know that distributors prior to 1957 are primitive. Electronic isn't the answer to everything and I am still running 6 volt and no plans to change. Personally I'm not a fan of electronic ignitions. It's not like I take this truck on 500 mile trips. Down the line if I see an issue I will address the issue. I drove it about 15 miles today and it runs great. Very responsive. I have 8 cars running multiple carbs. and not one has any electronic or MSD junk on it and all run good. If a person has unlimited funds all that electronic stuff and A/F meter are fine. Not for me.

Bored&Stroked · 03-01-2026, 11:27 PM

BTW, you don't have to permanently install an O2/AF meter, you can use the tailpipe method and a temporary 12V battery and just use it to tune, then take it off.

Sid · 03-01-2026, 11:46 PM

Yes. I am aware of that. It seems to be running clean right now. And I do realize the distributor is not proper. But for now it seems to be working alright. Maybe it is helping running progressive. There is an outfit in San Ramon Ca. that offers a distributor modified distributor with mechanical and vacuum advance 57-65 Chevy using Chevy points for the 8BA motor. I probably won't put 100 miles on this truck this year. I may check into this modified distributor next fall. $400.00 is a tough pill to swallow.

02-25-2026, 05:12 PM	#1
Sid Senior Member Join Date: May 2010 Location: Rathdrum Idaho Posts: 780	2x2 on 8BA flathead I have a 49 F1 with a stock flat .100 over and Edelbrock heads. stock cam. I have 2 deuce on it now but only running on 1 carb. I am going to get the other carb functioning. Running Holley 94's. I was wondering what jets and what power valves most found that work? Do you set both carbs. the same jetting and power valves? I am 2300 feet elevation.

02-26-2026, 06:53 AM	#2
Ziggster Senior Member Join Date: Aug 2018 Location: Ottawa, ON Posts: 1,373	Re: 2x2 on 8BA flathead I assume you’re going to go with direct/straight linkage. I just ordered some #48 and #49 jets and 5.5 psi PVs for my 2 x 2 direct/straight setup from Vintage Speed. I’m also going to try a progressive linkage. For that setup, went with #51 jets and a 5.5 psi PV for the primary. For the secondary, went with #48 jets, and a plugged PV for the secondary. I’m using a vintage Edmunds 2x2 intake which allows for the stk generator mounting. Charlie from Vintage Speed recommended the stuff for the progressive setup, and I just Googled the stuff for the direct/straight setup. Will know in a couple months how each works once the snow melts and I can get my speedster back Outside.

02-26-2026, 08:31 AM	#3
drfromnc Senior Member Join Date: Oct 2017 Location: Smithfield, NC Posts: 374	Re: 2x2 on 8BA flathead Im running #43 jets and 67 Pv on my dual 97s atop slingshot intake, Edelbrock heads, .125 over 59a, kiwil100 cam, straight/direct linkage. My elevation is about 150 ft. Engine runs like a scalded dog.

02-26-2026, 10:51 PM	#6
Flathead Fever Senior Member Join Date: May 2010 Location: Yucaipa, CA Posts: 1,492	Re: 2x2 on 8BA flathead Sponsored Links (Register now to hide all advertisements) It can take a little defective work to get the correct carb jets dial in. I'd start with what people are recommending for your cubic inches and go from there. I was a smog tech for 30-years and basically worked on computer-controlled feedback carbs. But you can do the same A/F testing with an O2 sensor on non-computerized carbs, then you can really get it dialed in to see how rich or lean you are at. Most people never do this; they just pop the carbs on and they run them with whatever jets they have. They might be close enough to run that way, but they could be so much better dialed in. I would look up some vehicles on YouTube and see how the people tuned them using a 02 meter. It will cost you a little bit for the sensor and gauge, but you will be able to see exactly what your A/F ratio is at idle, driving and acceleration. You also have to dial them in at idle, that is completely different than jetting the carbs. You want the idle A/F mixture screws turned out exactly the same amount, so both carbs are flowing exactly the same amount of fuel at idle, and both carbs' butterflies are opened up exactly the same amount. It's very important that both carbs are adjusted the same amount at idle. You can verify the idle mixture reading with your A/F mixture gauge. It can be done without the gauge but if you really want to be dead on correct and you don't have the experience of jetting carbs the A/F gauge will be a great help. Here's a video. There are a bunch of them on YouTube, some better than others. You need a hole in the exhaust as close to the engine as possible for the sensor. I used to do this for a living then I had a stroke. Now I have a bunch of my own cars to do this to, just don't feel like it yet. https://www.youtube.com/watch?v=D918ukEXXiU Here is another one. This is big old Holley, but this shows you how little changes help dial the carb in and how the exhaust gauge helps you getting it correct. Lots of changes before it's finally dialed in. Last edited by Flathead Fever; 02-26-2026 at 11:40 PM.

02-27-2026, 08:39 PM	#8
Flathead Fever Senior Member Join Date: May 2010 Location: Yucaipa, CA Posts: 1,492	Re: 2x2 on 8BA flathead Is there a way to “dial in” dual carbs using the A/F individually? Also, was cutouts to see if there was an “A/F app”, and sure if enough there is was, but the hardware/firmware is not cheap. As soon as you adjust the one carb it makes the second one out of adjustment. They have to be adjusted together. It really is easy to do it once you've practiced a bit. Be gentle with the screws, do not run them down into the seats hard, just barely until they touch and then back them out evenly for starters. You want to disconnect the linkage from the carbs but make sure each carb has a throttle return spring while you are doing this. You want to adjust the idle speed, both throttle plate barely opened up. As soon as you adjust one A/F mixture you've changed the reading on the other carb. So, then you need to adjust the second carb but then you have changed the adjustment on the fist. You just need to go back and forth and back and forth until the idle is correct and both the carbs are finally adjusted evenly, same number of turns out on the A/F mixture screws. Then you need to adjust the idle speed, how far the throttle plates are open on both carbs at idle, they need the same amount opening at idle, it won't be very much. You can use a uni-sync to balance the carbs. All this does is verify the throttle plate are set the same at idle. Then you might have to adjust the idle mixture screws "again". You just keep going back and forth until the idle speed is correct, the a/f mixture is correct, and both carbs Idle mixture screws are turned out the same amount. It sounds confusing but it shouldn't take more than a few minutes to get them all dialed. Then when you have the carbs set you need to hook the linkage back up to them, without moving the idle plates by adjusting the linkage. Then make sure the carbs open all the way up with the gas pedal floored. This is all just to get it running, you might need to take it apart and jet the carbs and do it all again. There's not much on YouTube. Here is a VW video on a uni-sync. All this is for making sure both carbs are open the same amount at idle. They were popular on VW's and foreign cars but come in handy on flatheads with multiple carbs. ttps://www.youtube.com/watch?v=FDm7EtmfOlM Last edited by Flathead Fever; 02-27-2026 at 08:54 PM.

02-26-2026, 04:21 PM	#5
Mart Senior Member Join Date: May 2010 Location: Solihull, England. Posts: 9,239	Re: 2x2 on 8BA flathead I run twin 94s on an 8ba manifold. This is on a 239 59A in my 33 coupe. I have stock jets which are 50s or 51s. I run stock power valves too. It runs great. I would suggest you try stock first and then try something else if it doesn't work. The thing is, 94s will run rich for many reasons. Running rich for any one of these reasons will make you try leaner jets and try and compensate. But that's wrong. You need to find why it is running rich. Float height. Leaking needle valve. Fuel pressure too high. Punctured float. Ruptured power valve. Wrong power valve seat shape. Wrong power valve gasket. Cracked power valve body. Warped lower and middle body castings. I have made videos showing machining the castings to ensure a good seal around the power valve vacuum chamber. A leak here will stop the power valve from closing and give an over rich mixture. When I did my dual conversion I first ran each carb on a single intake and made sure they both ran perfectly. Only then did I try them as a pair. I hope this advice is some use to you. There is a link to a 94 teardown and reassembly video here: https://www.fordbarn.com/forum/showthread.php?t=305182 Click the link in the first post Mart.

02-27-2026, 07:53 AM	#7
Ziggster Senior Member Join Date: Aug 2018 Location: Ottawa, ON Posts: 1,373	Re: 2x2 on 8BA flathead Is there a way to “dial in” dual carbs using the A/F individually? Also, was cutouts to see if there was an “A/F app”, and sure if enough there is was, but the hardware/firmware is not cheap.

02-28-2026, 06:54 AM	#9
38 coupe Senior Member Join Date: May 2010 Location: South Texas Posts: 2,135	Re: 2x2 on 8BA flathead The question not asked: what distributor are you running? The stock distributor works very well with a stock single carburetor. As soon as you use dual carburetors you need a different ignition advance setup. You cannot connect your stock vacuum advance to manifold vacuum, that results in the reverse of the ignition curve you need. Also, Innovate makes a clamp on O2 exhaust adapter that you can stick up the tail pipe and use without drilling a hole in your exhaust system. It works well as long as your exhaust system doesn't leak. I use one in a portable wide band setup I have so I can check carburetor adjustment without permanently adding an O2 gauge to a car. Search "Innovate O2 clamp on adapter" and you should find it offered by several different vendors.

02-28-2026, 11:33 AM	#10
john in illinois Senior Member Join Date: May 2010 Location: Illinois Posts: 2,249	Re: 2x2 on 8BA flathead You will be very close with stock jetting. John Lawson did dyno tests on 2 carb flatheads. His best runs were .046 main jets, .01 over stock for Stromberg 97s. Stock 94 should be similar. The only time this is not true is with restrictive small Air filters. They make it almost impossible to jet. As mentioned you also need a different distributor for 94s. John __________________ Welcome each day Last edited by john in illinois; 02-28-2026 at 11:56 AM.

03-01-2026, 10:51 AM	#13
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,906	Re: 2x2 on 8BA flathead A/F mixtures at idle are completely controlled by the two idle adjustment needles. Truth be told, I don't worry about A/F ratios at idle . . . I just adjust the idle mixtures and idle speed screws to get the engine to idle as I want it. Also, the idle mixture screws have nothing to do with the main jets, power valves and off-idle A/F ratios. Having an O2(A/F) meter is very valuable for main jet selection and even power-valve selection. Power Valves: If you're running dual carbs, usually you will want to reduce the power-valve selection to a lower vacuum number. Example: Maybe a stock single carb setup came with a #7 power valve and now (because of dual carbs) you may need to go to 5.5 power valves. The reason is that both carbs will see less vacuum and you don't want the stock power valves coming in too early (at a vacuum level of 7) and causing an over rich situation. Having a properly installed O2 (A/F) meter will show you your A/F readings at different throttle/load conditions. Distributor: As others mentioned, you should consider replacing your distributor with one that doesn't care about dual carbs. The stock "load-o-matic" distributor controls advance based on the specific vacuum signal of a single carb and stock engine - with a specific vacuum port off of that single carb (not the manifold). Your advance curve is probably way off, and you can't adjust it with the stock distributor. I'd find either a good Mallory dual-point or better yet, get one of the converted SBC distributors from Charley NY. His converted SBC distributors will typically have a vacuum advance canister as well - which can help with fuel mileage (if you care about that). Having a distributor with the correct advance curve can make a heck of a difference in overall performance, engine temps, etc. Last edited by Bored&Stroked; 03-01-2026 at 10:57 AM.

03-01-2026, 11:59 AM	#14
glennpm Senior Member Join Date: Sep 2014 Location: Mid-Coast Maine Posts: 3,346	Re: 2x2 on 8BA flathead Another good article IMHO "Modifying the Holley 94 two barrel for late model distributors" https://www.eatonbalancing.com/2010/...tors/#more-164 "The Holley 94 and 2100 two barrel carbs came as the standard equipment 2 barrel carbs on the 1938 thru 1956 Fords. When converting the distributors on the Y-Block Ford engines from the original Load-O-Matic (LOM) design to the later model Ford (1957 and up) distributors, the Holley 94’s original distributor vacuum port for the distributor will supply an excess of negative pressure or vacumm signal to the late model distributors. The original Holley 94/2100 carb port design uses an anti-spark valve as well as a speed sensing venturi port and a ported vacuum signal just above the throttle blades to provide the proper vacuum signal to the original LOM distributors. All three of these work in unison to supply a vacuum signal to the distributor even at full throttle with the LOM system. This is a good thing for a LOM distributor equipped vehicle but a bad thing for the later model distributors. The LOM distributors did not incorporate a centrifugal advance and relied solely on the vacuum signal supplied by the carburetor in which to maintain the proper advance curve under a variety of driving conditions. When using these carbs with the later model distributor which incorporates both a centrifugal and vacuum advance system, hooking up the vacuum advance without any carb modifications will provide an excess of vacuum signal to the distributor’s vacuum advance chamber at both idle and full throttle. This in turn creates tuning and drivabilty issues as well as increasing the propensity for detonation. Here is a pictorial in which to convert the Holley 94’s and 2100’s so that only a ported vacuum signal is supplied to the distributor and in turn makes this older model carburetor function similar to the ’57 and up carbs in both performance and fuel economy." __________________ Archives of historical but relevant older articles: ------------- Hover mouse over the links below and click! ~~~~~~~~~~~~~~~~~--------------- Rumble Seat’s Notes Techno Source for the 1932 thru 1953 Flathead Ford

03-01-2026, 04:14 PM	#15
69a Senior Member Join Date: Aug 2020 Posts: 323	Re: 2x2 on 8BA flathead I have a 49 F1 with a stock flat .100 over and Edelbrock heads. stock cam. I have 2 deuce on it now but only running on 1 carb. I am going to get the other carb functioning. Running Holley 94's. I was wondering what jets and what power valves most found that work? Do you set both carbs. the same jetting and power valves? I am 2300 feet elevation. The question has been asked, what distributor are you running. You cannot use the original Fordomatic distributor if you are using multiple carburetors. This is because the venturi vacuum is the only way the advance system works. It has no mechanical advance. If you are using 2 X 2 carburetors you have reduced the signal to the distributor by around 50%. There are several different solutions to this, but you need to let us know what distributor you have at the moment.

03-01-2026, 07:49 PM	#16
Sid Senior Member Join Date: May 2010 Location: Rathdrum Idaho Posts: 780	Re: 2x2 on 8BA flathead I do appreciate all the knowledge and input. I am running stock dist. I did the transformation. .050 jets in main carb. and .049 in the front. 6.5 power valve in the main carb. And now a 2.5 in the front tried plugging power valve but it wasn't happy so I had a 2.5 that I used. I did the linkage progressive so it opens up the front carb.at probably 1/3 throttle or so. I figured why be pushing excess gas while in town. I know it's not the way many of you would have did it but it seems to run very well. I drove it about 5 miles last night and pulled plugs today and they are a just shy of a dark cocoa. And the throttle is pretty responsive.

03-01-2026, 08:33 PM	#17
69a Senior Member Join Date: Aug 2020 Posts: 323	Re: 2x2 on 8BA flathead [QUOTE=38 coupe;2439810]The question not asked: what distributor are you running? The stock distributor works very well with a stock single carburetor. As soon as you use dual carburetors you need a different ignition advance setup. You cannot connect your stock vacuum advance to manifold vacuum, that results in the reverse of the ignition curve you need. You are NOT understanding the timing issue. The advance curve is now incorrect. There are several solutions available. I'm using a small block Chev HEI that I converted myself. There are new "plug and play" electronic ones on the market. There is also one that Tubman recommends, but I'm not familiar with that one.

03-01-2026, 09:04 PM	#18
Sid Senior Member Join Date: May 2010 Location: Rathdrum Idaho Posts: 780	Re: 2x2 on 8BA flathead Yes I do understand. The motor runs nice as is. Yes I could put an HEI in And maybe it will be better. Maybe not. And I do know that distributors prior to 1957 are primitive. Electronic isn't the answer to everything and I am still running 6 volt and no plans to change. Personally I'm not a fan of electronic ignitions. It's not like I take this truck on 500 mile trips. Down the line if I see an issue I will address the issue. I drove it about 15 miles today and it runs great. Very responsive. I have 8 cars running multiple carbs. and not one has any electronic or MSD junk on it and all run good. If a person has unlimited funds all that electronic stuff and A/F meter are fine. Not for me.

03-01-2026, 11:27 PM	#19
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,906	Re: 2x2 on 8BA flathead BTW, you don't have to permanently install an O2/AF meter, you can use the tailpipe method and a temporary 12V battery and just use it to tune, then take it off.

03-01-2026, 11:46 PM	#20
Sid Senior Member Join Date: May 2010 Location: Rathdrum Idaho Posts: 780	Re: 2x2 on 8BA flathead Yes. I am aware of that. It seems to be running clean right now. And I do realize the distributor is not proper. But for now it seems to be working alright. Maybe it is helping running progressive. There is an outfit in San Ramon Ca. that offers a distributor modified distributor with mechanical and vacuum advance 57-65 Chevy using Chevy points for the 8BA motor. I probably won't put 100 miles on this truck this year. I may check into this modified distributor next fall. $400.00 is a tough pill to swallow.