New to the flathead world and was wondering what the word on Holly 94's is. Came across a pair and am thinking of running them on the flattie. Any one have some experience with them?
I run Holly 94's on all our Flatheads. When I run two on a Flathead I block off the power valves. You'll also have to mess around with jet size to see what works best for your application.
94's are great carbs to work with and they are still reasonably priced compared to Stromberg's. If you are going to run two carbs just make sure that you rebuild them correctly. They need to be taken appart....completely...........take the throttle shafts out and inspect them as they will most likely be worn. You will need to lap all mating surfaces so they are flat and buy the best gaskets and rebuild kit you can. There are a number of people on this site that can rebuild them for you or give you hints and how to do it yourself. As far as blocking power valves on a dual carb setup, I'd try running them in both carbs, I personally don't see any benefit for blocking them unless you are going to run a tripower setup, then the secondary carbs idle circuits and power valves are blocked and they become just "dumpers". I can't stress enough, that if the 94's are rebuilt properly (not just throw a rebuild kit in them and expect them to work like brand new) they are a great carb, and you can even run a tripower setup on a stock motor.................with progressive linkage. IMHO
The powervalves on a '94 are designed to open at a certain level of vacuum. There are different sizes for the amount of vacuum that you are pulling. If you have a lot of overlap on your cam, you may need to go to a low numeric number. Plugging the powervalve serves no useful purpose. If you block the power valve, you have to open up the jets so it will run at top end, and then it is too rich at low end. No matter how many carbs you run, build every carb the same, and set each one up so that it will run well as a single carb. Then set up your multiple carbs and run the engine with a vacuum gauge on it. Note the vacuum at idle, and at cruise. If you can hold 8 inches or more at cruise, you can run stock powervalves. If it drops down lower, put in powervalves about 1 or 2 numbers lower than the vacuum you have. When you stick your foot in it, and the vacuum drops off, you want the power valve to open. For the jets, once you get the PV set up, take the car out for a cruise on the highway. After driving for a while, check a plug for color. You want a light tan for a driver, a chocolate brown for a racer. Bigger jets for darker color.
Here's what my flatty setup will be. This is a pair of 94's. If I run 'em both, I'll block one power valve. If I block off one whole carb, I won't do anything. My rod's going to be about fun and having it look cool, don't really care how fast it goes. 1 carb'll probably be fine for me. But 2 looks way cooler. Good luck, Pete
I've always run 94s, no problems. I have Bob at Baxter Ford Parts in Lawrence Kansas rework them for me. He even did a chromed pair for a showy 29 highboy we did for a customer.
Good information. One thing to keep in mind when running multiple carbs is that these specific carbs were designed to be run as a SINGLE CARB, not as 2x2 or 3x2. If you take a look at the factory cars like Ford, Chevy, and Chrysler that ran triple carbs in the 60's/70's...................some didn't run accelerator pumps or power vlaves...............for those of you who question the lack of an accelerator on secondary carbs, bear in mind that most of these factory tripower setups used no accelerator pumps in the secondary carbs. The 427/435HP tripower runs no accelerator pumps, and the three large Holley carbs on top of 406's don't even have a provision for one. The factory tripower setups that do run accelerator pumps generally required that extra squirt of gas because the carbs were opened by vacuum controlled linkage..................and as such were much slower than mechanical linkage.............that extra squirt was required to make the transition from primary to secondary with a bog. Just a thought to keep in mind when someone says that a tripower setup will not work and is really hard to setup..........................and that you should use use power valves in all three carbs...................not to say that if you do use a power valve in the secondary carbs that the setup won't work................................if you don't use the power valves in secondaries and rebuild the carb correctly....................it will perform much better and be easier to setup on the car. IMHO
Our 8BA runs just fine with it's stock 94. The only thing we had to do was replace the VERY WORN throttle body. I always thought I'd like to run a more "precise" mixer on that thing but I haven't found any alternative yet......the old Holley 94 just keeps workin'.
Hi Guys, Anyone here have some real life experience running triple 94's on a flat motor. I have a Harrell 3x2 and would love to run three functioning 94's if possible. I've always though the primary would be built as stock (maybe a lower opening PV if the cam is big) and the secondaries would be run with smaller jets and a blocked PV. How do you block the idle circuits on the secondaries with a 94? I assume removing the accelerator pump is as simple as not connecting it to the cam on the throttle shaft? I'm still having trouble with 2 94's so don't know how wise it is for me to be thinking of three Still puffs black smoke at idle with 4.5 power valves. Should try 3.5s? Danny
At idle, power valves are irrelevant unless they leak at their gaskets! They feed through the venturis. Lower floats a tad, turn in screws a bit. Idle has 2 circuits on it...actual idle, holes below throttles, and off-idle right above throttles. Total max flow controlled by idle jets, idle flow controlled by screws. Off-idle is WAAAY more important than you think. Mains and hence power valves cannot feed any fuel til way past 1,000 RPM on a SINGLE carb flatty since there isn't enough air flow to pull through venturis. You may well have a tremendous bog with no off idle...it's what the car is running on a lot of the time. At full throttle, richer mixture supplied by PV is needed...if no PV, main jets must be big to supply equivalent total mix, and any running at less than full throttle with those carbs open will be real rich. This is not just a performance handicap, it can reduce ring life to like 1,000 miles...very rich is BAD. Read up on what the circuits DO and THINK about this stuff! If you change/eliminate something, you have to either prevent its use at the RPM affected or put up with serious performance deficits! Jet sizes are largely based on venturi characteristics, NOT number of carbs. X amount of air going through gets Y amount of gas, so jet sizes and power enrichment needs will likely be pretty close to stock...if they aren't, you are likely trying to cover a problem by tuning a different circuit. Pumps...partially determined by engine size. Yes, this is the only circuit that multiplies delivery when you add carbs, BUT part of their function can be to cover the hole in performance caused by over carburetion when venturis are not yet pulling and off-idle isn't putting out...think of them as another tuning factor. A tricarb 427 Vette was not overcarbed, a tricarb flathead probably is...
Here's a good writeup by 286merc (who hasn't been seen online in ages) - it was posted here somewhere, but I couldn't find it, so I cut/pasted it from a saved file I had: Lots of confusion still remains about using Holley 94's and vacuum only distributors on 8BA's and early Y blocks. I'll just talk about the 1948-54 8BA style distributor. Over 2 years ago I got into a discussion with an expert on another forum who positively stated that you could not run dual 94's and a stock distributor. When I said I better take my setup apart then all hell broke loose. A few others keep referring to an outdated 1954 magazine article like it was some type of gospel. First of all there are over 17 varieties of the 94 style family, starting back in 1938 with the Chandler Grove and ending with the 1957 Y block for Ford production. Generic parts store replacements were available well into the 70's. The Y block versions differ from the true 94 ( which is the .094" venturi diameter) since they have a 1.0" and 1.062" venturi and often have a 1 or 1 1/16 marking on the side. There was even a 1 1/8" version available that was quite common on hopped up VW's. The CFM of the 94 family varies from 150 to 190 for ones used on Ford vehicles. The larger venturies will give a slight power increase in even a mildly modified engine. <O</OBefore attempting a tear down get a copy of the Ford procedure and a detailed parts blow up. It is part of the Shop Manual but some arent as detailed. The 1952 car manual or the aftermarket 1952-54 combined version is the best IMO. <OI always suggest that users start with a matched pair of casting models that have the vacuum port on the lower right side of the bowl; you can not use the earlier versions without a vacuum port with the stock 8BA distributor. These carbs carry bowl ID's of 7RT, 8BA, 8RT, EAA, EAB, EBU, EBV, ECG, 2100 and probably some I missed. <OAnother thing to check for is the nozzle bar, there were standard and hi-lift nozzle bars; dont mix types. The Shop Manuals suggested show the differences quite clearly. The drill bits specified for cleaning passages can be found at hobby/model shops. Guitar strings are good alternatives should they be handy. After a thorough cleaning, check for any cracks, warpage or corrosion, repair or discard the bad piece. One old tried and true method of truing up the bowl and air horn surfaces is to place a clean sheet of 220 grit wet/dry paper on a pane of glass and gently slide the part over it; visually look for low spots. Finish off with 400 grit for a nice smooth surface. It is always good to have several parts carbs. Next step is to rebuild them exactly the same. Dont be suprised by what you will find inside of that flea market goodie, parts were often swapped without consideration of correctness even in carb shops. Just do both the same and to original specs. Spend a little extra time polishing up any interior mold roughness; a Dremel works great for this. <ONext is the throttle shaft. For dual carbs using drivers side linkage you need extended throttle rods. These can be found on many early and later carbs that used a hand throttle. Quite common on trucks. Ford says .008" wear is OK but that usually also means the base casting is egg shaped by now and leaking vacuum like a sieve. The first step cure is an oversize shaft and a reamed base; try for a .002" fit. In extreme cases you will have to bore out the base and fit a bushing that should be a bit undersize and reamed to fit; getting everything realigned can get tricky. Several Internet and Hemmings advertisers can supply the needed parts or even rebuilt bases. <OThen pay particular attention to fitting the butterflies to the throttle bores. That fit is VERY important and you might need to have several extra carbs (of any ID) on hand to find the tightest fit. I like repeating myself about spare carbs. Hold up to a light to check, there should be the tiniest sliver of light visible. Also be certain the bases arent severely pitted and butterflies corroded on the edges, a sure source of vacuum problems. Leave the choke plate in place for both carbs. Altho only one will be choked the plate is required for good air flow direction. Tests have shown a hp loss without the plate. Next comes the true test, tuning them up. I like to start with only one carb mounted with a known good air filter; not some restrictive import. Securely block off the other hole. Temporarily block off the vacuum line. Start the engine and adjust the carb for a good idle, be sure there are no vacuum leaks on this carb and over at the block off plate. Dishwashing liquid and water mix in a spray bottle works great. Do not ever use WD-40 or other flamable liquid. Warm up the engine and secure the choke wide open. Now hook up a vacuum gauge to the carb port; dont even think about running duals (or trips) without one. Assuming the engine is tight, there should be around 18"/hg at idle. If its much lower then its time to trouble shoot. Im assuming a non full race competition cam. Rev it up a bit, the vacuum should hold fairly steady thru at least 2500 rpm. Note that Im leaving the distributor vacuum off for now and not worrying about the advance. If you are absolutely/positively sure the distributor is perfect then hook it up if it makes you happy. I personally prefer as few possible problem areas at this stage. If everything is OK then swap carbs and repeat. Its a lot easier to get the idle set this way than with both in place plus you can find problems easier. And not place the blame on something else later on. If you havent installed the new intake yet then by all means do the initial adjustments on the stock one. Now mount both carbs but no linkage. Get out the Uni-Syn that you should have bought along with the vacuum gauge. Use the Uni-Syn to measure/equalize air flow of both carbs AND the vacuum gauge to set final idle mixture. Final result should coincide with maximum vacuum. Then hook up the linkage and do it all over again. This step assures that the linkage is not applying any control to the throttle rods. Tighten down the stops. Be sure you pay attention to blocking off the not in use vacuum port. Only the front carb will be needed to provide a vacuum signal to the distributor. By this time you should have 2 almost identical carbs. Use clean, fresh and well filtered gas. If using an electric pump set the pressure regulator for 2.5 lbs maximum. Hook up the choke cable to one carb, usually the rear. Hook up the vacuum line from the front carb to the distributor. Hook up the vacuum gauge to the rear carb; the original readings should be pretty close. If not check for hose or diaphram leaks. Now its time for Truth or Consequences. Extend the vacuum gauge hose into the vehicle. I prefer to have someone else do the reading while I pay attention to the driving. Record the readings throughout a full driving pattern, from idle to wide open throttle as you go thru the gears. How does the response feel? Any pinging? Stumble or excessive loading/bogging down? The ideal is to have the power valves open only at or near full throttle. Many of you may not ever want to wind things up that hard. If you are staying above 7-8" thru all phases of your way of driving then chances are you are good to go. Stock Ford power valves are 7.5's which means that at that vacuum they open. Tolerance is roughly 1 point either way. If not then it will be necessary to go to a numerically lower power valve. This may raise a few eyebrows but try only one at first; the staggering effect may be to your liking. The front 2 cylinders are often starved with stock and some aftermarket intakes. Fuel flow is a hit and miss operation with all but the best designs. In most cases a pair of 4.5's will handle all but the hairiest cam street engines. I run 4.5's on my 286 and 5.5's for many customer built 276's with Schneider .395" cams. Go to the Holley Technical web site; power valves havent changed nor have the jets for almost 65 years; any speed shop can get what you need. Lots of good info on the Holley site. The worse thing you can do is to plug or otherwise defeat the power valves in this configuration. Running 6 or 8 carbs on a hemi is something altogether different. Once you're sure that the valves arent dumping too early then put in a fresh set of plugs and take a half hour ride at highway speeds. Read the plugs and change jet sizes ONLY if absolutely necessary. One size either way should be enough. Stock jets at sea laevel are .051; .049 and.047 were used at altitudes in the 5000-15000 foot range. Sometimes changing to a different heat range or brand of plug is a better move. NKG BL6 plugs give me the best results and consistentcy. This is all called fine tuning. So yes, dual 94's and a stock vacuum distributor are compatible a good many times. Dont expect to go racing or expect reliable fire beyond 4000 rpm; this is still a compromise. If you want a bit more advance (or reduced lack of as the distributor runs backwards from the typical vacuum operation) then turn the spring pins on the top of the plate with pliers. They are an eccentric and the spring tension is adjustable. There are numerous conversions and aftermarket ignition options available; it just takes time and money. The above was a compilation of over 45 years of using these carbs on flatheads and overheads, plus several articles in HRM and others going back as long, and finally some of the more recent books. I would recommend Tex Smiths Flathead manual as good reading altho it is not without errors and omissions. This article will also be usefull in some areas when using 3 carbs, however there are differences involved. Thats another article for down the road. I hope I havent made too many typos or any glaring boo-boo's, Ive been editing and typing this intermittently over about 3 hours.
When I got the car it was very hard to start. It would flood at the drop of a hat. It is a dual carburetor setup on a Fenton intake manifold. When I rebuilt the carbs I used two 3.5 power valves. I have not noticed excessive pinging when accelerating. To start the car I set the choke on full on one carburetor and pump the gas petal twice. It just starts right up like a car should. The engine is a 48 flat head that my dad bored out and put a performance cam in. The car is a 34 ford 5 window coupe. It is a very basic hot rod like a young man in the 50s would have. Rich
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