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Old 04-05-2011, 01:14 PM   #1
Slick Willy
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Default ANOTHER 94 dual setup question! (just a bit different)

So I did a search and found ALOT of info on 8ba and 59ab setups. My question delves into the wonder world of my '37 21 stud!
This motor ran great with a single carb on a regular dual offy intake with the rear carb plated off.
This year I want to get both carbs going. I will be adding an electric fuel pump and a regulator. This is the rundown..should I change anything first or just go with what i got?

engine:
'37 21 stud bored .040 over
stock cam
original divebell dizzy with vac brake converted to 12v
aluminum heads milled .030
carbs:
offenhauser reg dual intake with 2" carb spacers
2 rebuilt 7RT ford 94s
51 jets all around
blocked power valves(both)
one is set up for primary with choke other is not

I ran the carb with a velocity stack and screen(no filter)

I live AT sea level and rarely drive at any significant elevation.
I guess my main concern is matching PVs and jets to my needs. Im rather green at fine tuning carbs, apparently Ive just always been lucky.
Thanks again for any info!

Last edited by Slick Willy; 04-05-2011 at 01:45 PM.
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Old 04-05-2011, 02:52 PM   #2
Mart
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Oh well, here we go again.

Here's my experience.

I got a vacuum gauge and watched the vacuum as I drove along. I get 20" plus at idle, and it runs along under light accelleration at about 14 - 15".
I can see no reason not to run stock 7.5" power valves.

I have holley 2100's with 1" venturi's, and use 52 jets.

I tried 4.5 and 3.5 power valves and the 7.5's feel better.

I'd say twin 94's on 21stud with 51 jets will be fine, and depending on your vacuum reading when just driving along or accellerating very gently, go with a power valve rated at about half that number.

One other thing - make sure you use the old type needle valves, the new ones leak and make the carbs flood - hence preventing accurate tuning.

Also a stock fuel pump will be more than adequate for your needs, if in good shape. Although an electric pump can be handy for priming if it has sat for a while.

Not just my opinion. but first hand tried and tested experience.

But others will have different opinions and combo's that work for them.

Mart.
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Old 04-05-2011, 03:09 PM   #3
Bruce_MO
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

I just made an upgrade to my two 94's on my '53 EAB engine (Offy intake & heads, Fenton headers, mallory distributor, stock internals)...switched to 4.5 power valves from stock. It made a major difference in everything from idle to mid-range throttle. I have 049 jets. I was previously plagued with fouled plugs, running rich and stumbles from idle. Now it runs beautifully, and I only changed the PV's.

I agree a stock fuel pump is fine. But I'm installing an airtex electric pump because of vapor lock concerns and hard starting after sitting for a long time. Airtex now makes a pump with 3-5 psi output pressure, so you won't need a regulator. The pn was #8902. There was a small article in the back of the latest V-8 Times with informtion about it. I paid $40 + shipping from Woody's-Auto-Supply.com.
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Old 04-05-2011, 03:38 PM   #4
Slick Willy
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Hey Mart, thanks for your dual responses! here and there...With my older more stock motor, the ford barn seems more like home! The HAMB gives me a wider range of possibilities. I knew there was alot involved to multi carbs, I just hope Im not in over my head!
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Old 04-05-2011, 03:44 PM   #5
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Bruce, Im planning on running the small EMPI fuel pump for vw's, theres no pump on the motor. I just ran the gravity feed to a single carb
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Old 04-05-2011, 03:45 PM   #6
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

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I think there are a lot of things that can cause mis-diagnosis.

Flooding carbs. - been there.
Incorrectly seated power valves.
Overtightened (cracked) power valve - had one of them too.
Badly seating needle valves - tell me about it.

If all of the above are right, then you can make a educated judgement on the rating of the power valves. If any of the above are present, then it will skew your judgement.

Mart.
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Old 04-05-2011, 08:59 PM   #7
Mike in AZ
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

regulator with pressure gauge to make sure the regulator is doing its job correctly.....good luck and have fun....Mike
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Old 04-05-2011, 09:22 PM   #8
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

From my personal experience if you are using progessive linkage it is critical that the throttle plates completely seal against the bores when closed. I ran out of bases to achieve this. I had trouble trying tune out the vacuum leak at idle. I then tried leaving the idle circuit active in the secondary. Idle was tunable but off idle was not consistant, kind of rolling while cruising. When the secondary came in there was a firm stumble before the power came in. The stumble was present with #51 jets in both carbs anrd the following PV combos: 1- 7.5 in primary and secondary, 2- 7.5 in primary plugged secondary, 3- 3.5 in primary and secondary, and 4- 3.5 in primary plugged secondary. The linkage was set to open the secondarys starting at 60% of primary opening. Decided to give up on the progressive and set the carbs direct with 3.5 PV and #51 jets. Good idle and a slight off idle stumble. I figured the stumble was from being rich. Got a recommendation from KenCT to use the set up with #47 jets. Made the jet change and it runs very well. good idle smooth accelleration and cruise.
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Old 04-05-2011, 10:02 PM   #9
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

I use an A/F meter to set carb jetting. A good one will follow the PV.
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Old 04-05-2011, 10:14 PM   #10
flatjack9
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Quote:
Originally Posted by Bruce_MO View Post
I just made an upgrade to my two 94's on my '53 EAB engine (Offy intake & heads, Fenton headers, mallory distributor, stock internals)...switched to 4.5 power valves from stock. It made a major difference in everything from idle to mid-range throttle. I have 049 jets. I was previously plagued with fouled plugs, running rich and stumbles from idle. Now it runs beautifully, and I only changed the PV's.

I agree a stock fuel pump is fine. But I'm installing an airtex electric pump because of vapor lock concerns and hard starting after sitting for a long time. Airtex now makes a pump with 3-5 psi output pressure, so you won't need a regulator. The pn was #8902. There was a small article in the back of the latest V-8 Times with informtion about it. I paid $40 + shipping from Woody's-Auto-Supply.com.
Obviously your old power valves were not working properly.
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Old 04-06-2011, 08:39 AM   #11
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

SW,
Ol Ron hit it. My recent few days working with a dynomometer
shop dialing in multiple carb setups on Flatheads opened a new world to
these 70 year old eyes. Each motor has its own likes and dislikes but
in general it seems you can get a good start with certain jets and PV's.
On a 296 Flathead with a big cam we settled on 53 jets and
3.5 PV's. The 53's held the air fuel ratio at 13.9 to 14.1 from idle to about
2800 ,after that the AF ratio went lean.....I installed 3.5 PV's in both carbs
and the AF ratio settled in at the mid 13's above 2800. Max HP and
torque came in at about 4100 rpm, 162 hp, 207 torque.
I guess what I saw tells me that in general AF ratios could be
compromised with big number PV's . Even the 3.5's were a bit rich in this
big Flatmotor.
The dyno doesn't lie and the AF meters are looking right into the
chambers. Ron knows.
The next motor was a 276 incher but that's a story for another
day.
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Old 04-06-2011, 11:59 AM   #12
Slick Willy
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Thanks everybody! Im getting a better idea of where and how to start.
As you can see though, most of the info and feed back deals with big cube wild cammed motors. Mines just a little guy! Thats why I ask about it, to see if Im in the ball park. I know its all relative.
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Old 04-06-2011, 05:09 PM   #13
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Sw,
After shaking all things out I'd go with 41 Ford 1. The 47 jets
seem a bit small but with 221 cu in give it a whirl. It's real tough to
read the plugs accurately with corn gas but if they are BONE white
go bigger.
OMHO.
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Old 04-06-2011, 07:02 PM   #14
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Ok, swap out the 7RT, 94s with a pair of Stromberg 81s, your engine will love them..
Duane..
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Old 04-07-2011, 06:42 AM   #15
Charlie ny
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Duane,
How are things in Sacto ? I have about 400 94's wanna swap for some of your 81's.
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Old 04-07-2011, 10:18 AM   #16
JWL
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

I don't understand the description about the large number power valves versus the smaller number?? The larger number PV would allow fuel into the fuel channels earlier(at higher vacuum readings) than the smaller number PV. So, if the engine went lean at 2800 because vacuum closed the higher number PV, it means the lower number PV would have been closed well before the higher number valve, This would put the engine lean at, perhaps, 2500??? The lower or higher numbers on the PV should have nothing to do with the amount of fuel metered, but rather, at what point in the vacuum reading the fuel is allowed to transfer into the PV channels.
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Old 04-07-2011, 10:52 AM   #17
Bruce Lancaster
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

All discussions about Ford power valves are hopelessly muddled by odd interpretations of their role..."bigger" and "smaller", they "dump" in fuel, they somehow relate to misture at idle, etc.
The discussions are endless and all end in hopeless confusion. No one should be allowed near these messes without first reading the Ford service bulletin that explains how the circuits work...
We are looking at the big difference between buying a book and asking on the net here (and I'm WAY late in getting hold of JWL"s book!). Internet hands you 25 positive answers, book only gives you one... and if you haven't read a book, howinhell are you going to sort all those different answers??
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Old 04-07-2011, 05:15 PM   #18
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

Right on, Bruce!
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Old 04-08-2011, 09:32 AM   #19
Charlie ny
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

A bit of clarification here...at the direction of my customer I built these
94's with NO power valves. So the sole source of fuel was the 53 jets.
The addition of the 3.5 pv's was from originally no PV's at all. I hope this clears up things.
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Old 08-29-2011, 11:32 AM   #20
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Default Re: ANOTHER 94 dual setup question! (just a bit different)

I'm running a 239". Got two 94's w/ a 3.5 PV & a 7.5 PV. The jets are 52's. Set up with a vacuum gauge & A/F ration gauge. Works real well.
Butch
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