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Basic Flathead/Generator question...

Discussion in 'The Hokey Ass Message Board' started by 3blapcam, Mar 6, 2006.

  1. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Working on my buddy's '50 w/ rebuilt 8ba & running dual 94's w/ size 49 jets & two 4.5 in/Hg power valves right... we have done a 12V conversion, but the Gennie isn't charging. Car is running rough... do ya'll think that's due to the Gennie not working? I think it is, and we're getting it rebuilt today.

    What's got us confused is we're trying to tune the carbs, but the car isn't running well enough to get any real information. He took it on about a 10mile round trip, and the plugs looked great, but then it fouls them at idle. That should be a case of the idle/air adjusters needing tweaked, right? We don't have a fuel pressure gauge on it, but it's got a stock pump feeding the carbs.

    Any help or experience here would be very helpful.

    Thanks,

    Alec.
     
  2. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,007

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    I'd start by getting your Dizzy and voltage regulator working correctly.
    Are you running the original dizzy??
    If so there could be problems with your advance.
    286merc has a tech article on your problem and the things needed to get your setup running properly. Found in the tech section under
    Flathead Manifold review Tech-o-matic


    The KEY to using 94s by 286Merc




    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 A few others keep referring to an outdated 1954 magazine article like it was some type of gospel.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 272 Y block for Ford production. Generic parts store replacements were available well into the 70's as the Holley 2100 and 2110. 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" aftermarket version available that was quite common on hopped up VW's. The Lincoln V12 had a LZ casting which was also a 1" venturi. Bendix and Stromberg even got into the act, a Stromberg 94 clone actually has 97 on the side and is often found on EBay selling as a true 97!

    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 stock or mildly modified engine.

    Before 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.

    I 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, 2110 and probably some I missed. If you decide to use any of the Y block carbs then remove and plug the spark control valve in the base.

    Another 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.

    Next 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 1948 and later trucks as well.
    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.

    Then 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. The Y block plates are slightly larger than the flathead versions so dont get them mixed up. 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. ALSO be sure you dont reassemble the plates backwards!

    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 and at the manifold ports. Dishwashing liquid and water mix in a spray bottle works great. A leak sucking vacuum will cause a stumble, an air leak will cause bubbles. 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 it's much lower then it's time to trouble shoot. I'm 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. Tweak the idle mixture screws for maximum vacuum and a smooth idle, actual rpm is not important but it is a lot quiter down around 5-600 rpm.

    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. There are other balancing devices available, if you are familiar with their operation then use them.
    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 when they are needed to enrich the mixture. This will be at or near full throttle or under a stiff load like going up a hill. Many of you may not ever want to wind things up that hard. The previous was intended more for stockers who are usually not going much beyond 2500 rpm. For rodders use the 2500 figure as a good place to start opening the valves.

    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 new Holley "Hi Performance" PV's will work but require a bit of filing to clear.

    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 level 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 since the distributor is not receiving the vacuum signal it was designed for. 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 useful in some areas when using 3 carbs, however there are differences involved. Thats another article for down the road.



    Ive made a few minor edits to the original article as it was strictly 8BA specific. There is no reason you cant use 94's on the earlier flatheads either, the requirement for matching still holds but you can use any variety. Simply plug the venturi vacuum port and the spark control valve on Y block types should be removed and plugged.

    ------------------------------------------------------------
    And here is some more 94 trivia that I wrote for a nailhead guy:


    The Holley 94 was developed for Ford in 1938; the initial design was from Chandler-Grove but Ford screwed them out of the big production contracts. The CG is quite scarce. There are at least 17 varieties between then and the 70's. Ford stopped using them in 56/57 and by that time they had 1 1/16 venturies. Aftermarket went up to 1 1/8 venturies.
    Parts and kits are readily available, power valves and jets are the same as modern Holley's. Main problem areas are worn throttle shafts and corroded throttle plates; sources of vacuum leaks.

    When running 2 or 3 carbs you do NOT want to block the power valves. Instead select a power valve rating that opens at WOT or a selected low vacuum level.

    If the 6 are going to be used on that log its best to have them all the same casting ID as there are flow differences. After 49 you also had standard and high lift nozzle bars, and a venturi vacuum output which needs to be plugged.
    The 59, 99, and other pre 1949 castings were popular as they didnt have all the differences. Mixing the models up gave the 94 an undeserved bad reputation that the uninformed still believe today.

    Tuning requires a UniSyn, available most speed shops, on-line, etc.
     
  3. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Thanks Petejoe... I think I've read that article about 3-4 times, and printed it twice ;o).

    Actually, the car has a Mallory dual point w/ mechanical advance. I've checked to make sure the points are breaking, but haven't gone as far as checking the weights. I don't know that's not the problem, but I don't think it is either.

    Alec.
     
  4. Stafford
    Joined: Feb 15, 2005
    Posts: 109

    Stafford
    Member
    from N. Georgia

    It could be that your power valves are leaking. On my 2x94's I ran for 4 or 5 years , I ran 6.5's in them and it ran great. I think you may be jetted a little rich but I wouldn't swear to it. I have 3 97's now and Uncle Max set them up with 45's in them and they run fantastic. I'll look today when I get home and see what jets the 94's have in them. Now this is the critical part, you'll never get it to run right if you don't get your throttle plates closed all the way at the same time. Then move each idle screw say a 1/4 turn at a time till you can get it to idle. if one of them is open more than the other one it'll run like crap. While it's idling , with the breathers off, lookd down in them and see what you can see. If one of them is drizzling fuel from the high speed nozzles I'd bet that carburetor is open more than the other one. Good luck, Stafford
     

  5. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,007

    Petejoe
    ALLIANCE MEMBER
    from Zoar, Ohio

    The article also gives info on a good start of powervalve and jet sizes and what needs to be done with tuning them regardless of the dizzy advance type.
    Instead of trying to shoot for finding the direct problem, in a consistant manner, eliminate the non problems and that way you'll be assured you dont have a twofold issue. Get some good juice to the ignition by being sure your Dizzy is operating correctly. Then check for the proper advance curve. then go to the carbs. Hope this helps.
    I'm sure others here will throw in there thoughts too.
     
  6. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Hmmm... very insightful! I'll check that out, because I haven't verified for sure. It actually idles fine, it's just loading up. We have an MSD 5 box on the car, and that may be what's keeping it running. When the plugs were clean from our drive, it almost looked like it was lean if anything because they were so damn white & clean! It's just idle & under full throttle that the car is acting up.

    I thought about the PV's leaking... and I don't think they are... they looked seated in the carb.

    This is my first flatty to really play with, but on my OHV motors, if the coil was going bad, it'd scatter the spark at higher RPMs and run like crap. I figured we'd be getting a similar response from running on just the battery. The only thing that has me thinking otherwise is all the race cars out there that make passes on just the battery & no altenator at all.
     
  7. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    Yeah, you're right. I've kinda used it as a guide for jets & PV's. The only thing we're really lacking to tune it correctly is the vacuum gauge. I've been on my buddy to buy one, but he hasn't done it. I guess that leaves it up to me to buy one, huh?!
     
  8. 3blapcam
    Joined: Jul 15, 2004
    Posts: 526

    3blapcam
    Member
    from Austin, TX

    For those who put in their 2 cents and for those who just read the thread... It was the plate inside the distributor that the points sit on that was loose and that caused it to run like ass.

    Gennie is 12V now and the dizzy is good-to-go... and after an extensive roadtrip downtown it survived... and ran like a champ! I think we are 100% ready for the roundup now!!!

    Alec.
     

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