stumbling 94's

a friend introduced me to the HAMB drags. own a 57 but got hooked on hot rods. Built a 31 with a283 , faux six pack of 94's , but only center two operational, and linked for tandum operation together. bought as rebuilt package from well known on line dealer.
Stumbling is the problem. called the company, found out carbs were not furnished with power valves, and the reason is that since they operate together at the same time you have double squirters.and double squiters and double power valves equals flooding. i haven't been into the carbs.

My questions are for those in the know. I'm trying to get this car to KKOA, and i'm running out of time
is the power valve story logical or true?

is it OK to run vacuum line from on top of the manifold?

idle mixture screws at about one turn
installed idle adjustment screws thinking it was getting too much fuel. ran fine at idle but crack the throttle and it will damn near die. seems like the more i backed them out the more responsive it became

been running rich(black plugs)
i know it's been talked about before, but need clarification on 2 carb setup

 

Been helping a friend with two 94's on a warmed flathead Merc. He was told to take out the power valves, wrong. He is running a power valve in one carb. His plugs were also black soaty on one bank. Not trying to start a war. I think of the power valve as a mid range enricher, when the vac. equals the power valve it starts dumping fuel. If your plugs are black and soaty with no PV you carbs are to rich. Check your existing jets for size, they are marked. You should down size the jets, if yours are 52's put some50's in. Do a plug check after each change. Buy or borrow a vacuum guage, once you get the jetting closer attach the vacuum gage, now try adjusting the idle mixture screws to the highest vacuum reading.
This should get you headed in the right direction. Patience and changing jets and PV is time consuming. Good Luck

 

Are you looking for a drivable tune, or just all out for the drags? If you want something drivable, you'll want a part throttle enrichment - power valve. However, with two carbs you change the vac signal rate of drop when opening the throttle, so you'll typically use power valves with a lower opening value. You might wind up with a PV in one, or both carbs. 94s don't flow that much, so just two on a 283 isn't much carb.

 

On my 265 inch flathead and middle of the road cam, I am using 5.5 power valves. Smooth as silk on summer fuel. slight stumble on winter fuel.

 

START OVER with whatever jet size was stock in your carbs. Tell us model of carb...on L side of bowls, oft jet size is STAMPED around back. Probably around .49-.50.
Put in PV's, make sure they actually seal where they tighten up to bowl.
You may need to change PV from stock 7 or 8ish, maybe not, this is not an overcarbed setup!! but ANY power valve is better than none!! Full throttle require DIFFERENT MIX than part throttle, just jets CANNOT be right for both.
You probably have little chrome aircleaners. Tune the thing WITHOU the air cleaners, if anything then changes you know that the cleaners are junk and will kill your engine while killing the mixture.

Idle is NOT a setting like X turns out, it is tune til engine is happy. Disconnect linkage, get engine idling and warm, set an idle speed that sounds OK. Turn the 4 screws in and out VERY SLOWLY til you get a warm fuzzy idle. You will likely have to turn idles down and go around again several times as you get close to right. Once all is happy, hook up linkage without moving the throttles so idle stays where you have it.

 

Dual carbs that are not progressive, flow 1/2 of the needed capacity at any time. They should be synchronized so that each side is matched. I run dual 97s on my Stude engine and they are just stock. The engine has no idea how many carbs are on the engine. All it knows is the amount of air flowing through IT at any time. It was designed at the factory to add a certain amount of fuel for the air passing through it.

 

Just re-read the advice you got from the "well known online dealer"...
Holy Cow. Delete any brain cells devoted to THAT. 10 minutes of research will enable you, perhaps, to tell them how a carburetor works.
By the way...most stumbling is fro air without enough fuel...jets and power valves DO NOT "squirt"...on and on and on...

 

Take a look at Bruce's first post in this thread.

Start over with an absolutely stock calibration for the 2 carburetors you are using. This definately includes power valves. Using a stock calibration you have a repeatable "baseline" and you can now tune KNOWING that you can always go back to your baseline.

Once you have the stock calibration, synchronize the airflow through both carburetors. Failure to do so will give issues.

And in the FWIW category IF the end carbs were hooked up, AND you were running progressive linkage, then plugging the power valves is a good idea; but NOT on the center carb(s).

Jon.