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  1. #1

    Question Carb Tuning & Drivability, Need Some Guidance

    Hoping to appeal to the experts here for a bit of advice.

    Over the last several years, I have been slowly trying to dial in the tune on the 347 I built and installed in my 85 GT. I have done a lot of research, reading various forum threads and online magazine articles, but very little of it seems to focus on tuning for street applications or goes into depth on anything much other than idle mixture screws and main jets. Though with what info I have found I have been able to get my car running decently. I installed a wideband A/F ratio gauge last year which has helped me a great deal. Primarily, my focus has been on the idle and transition circuits. Ive piddled with the primary and secondary main jets some to get them in a tolerable range, but they are still slightly on the rich side for now. Trying to get a clean idle and cruise, good throttle response, and reasonable performance.

    At this point Im seeing the following A/F ratios on idle and transition circuits:
    -Idle, cold (choke closed, fast idle) 13:1
    -Idle, warm-up (choke open, normal idle speed) 15-16:1
    -Idle, fully warm 12.5-13:1
    -Transition, warm-up (steady cruise) 14:1 climbs to 17-20:1
    -Transition, fully warm (steady cruise) 13:1

    My main problem is with transition cruise during warm up driving. After accelerating to speed, with engine RPM between 1500-2000 or so, the AFR will initially settle around 14:1 then after a few seconds start getting leaner and starts misfiring. I have to keep rolling in the throttle a bit until its fully warm. With the current settings, the car runs well when fully warm. Are these AFR numbers normal? Id like to see the warm numbers a bit leaner if possible, but worried about the cold AFR getting any leaner than it is. I know numbers arent necessarily everything.

    From a drivability standpoint, is this normal with a carb? Have to deal with the leanness issues until its warmed up? I do let the car warm up in the driveway for a while before driving. Maybe Im too accustomed to my newer fuel injected cars, just find it a bit irritating having let it warm up then it runs like crap for the first 10 min. of driving. As of now, this is the best the car has run since Ive owned it. Trying to make this run as well as possible.

    Im currently running an open-element air cleaner. Would refitting the stock air cleaner w/snorkels and heat risers help with cold drivability? May take some modifying to fit with strut tower brace, though. I could see how a warmer air charge could richen up the mixture with the engine cold and the colder air charge could lean the mixture when the engine warms up, at least in theory. Not sure how much difference this would actually make. Tempted to do this whether it will help or not.

    Would going to a non-air-gap manifold be a worthwhile change? Would consider this to be an absolute last resort change. I've read of some people having issues with air-gap manifolds on the street, but others not so much. Matter of opinions, I suppose.

    Any other suggestions I could try to increase cold drivability? Im running out of ideas.


    Engine Setup:

    -10.5:1 C/R
    -AFR 185cc Heads w/ 58cc Chamber
    -Cam: .526/.532 Lift, 214/222 Dur @ .050, 110 LSA
    -PP Crosswind Intake (Perf RPM Air-Gap Equiv.)
    -Holley SA 670cfm Carb
    -Stock Duraspark II Ignition & Distributor
    -Vacuum:17-18in. Hg Idle / 21-22in. Hg Cruise / 19in. Hg OD Cruise

    Current Timing Settings:

    -Initial: 14 deg.
    -Centrifugal Adv.: 22 deg.
    -Initial + Centrifugal (Total): 36 deg.
    -Vacuum Adv.: 12 deg. (on manifold vacuum)
    Note: Not positive about timing curve (cant watch tach and operate timing light by myself), but using the factory(?) light and heavy springs. Guessing its probably all in by 3500 or so.

    Current Carb Settings:

    -Floats set w/ fuel level @ bottom of sighthole
    -Fuel pressure @ 4-5psi
    -T-slot square (~.020 showing)
    -Idle Screws: 5/8 turn out
    -IFRs: .0225P/.028S (.026P/.028S Stock)
    -IABs: .079P/.050S (Stock)
    -MABs: .028P/.025S (Stock)
    -68 Primary Jet (65 Stock)
    -72 Secondary Jet (68 Stock)
    -9.5 Power Valve (6.5 Stock)
    -PCVR: .035 (.055 Stock)
    -.031 Acc Pump Nozzle
    -Orange Pump Cam, #1 Hole
    Note: PCVRs, IFRs, & Primary IABs have been drilled/tapped for set screw restrictors/bleeds.

    Current Engine Compartment (for what its worth)


    Sorry if this is a little long, trying to give as much info as possible. Will be happy to provide more details if needed.

    Thanks in advance for any insight,

    Thomas
    Last edited by 85MUSTANGTGT; 07-08-2017 at 09:44 PM. Reason: fix photos

  2. #2

    Default

    With the open air filter breathing from engine bay I don't think you will get a best of both worlds. I would either make some kind of cold air kit or focus your tuning on when the engine is fully warmed.

    Also, what fuel pump and reg? Can you read fuel pressure while driving?

    I cant believe a cam that size pulls that much vac too.
    Brian R. of Michigan
    83 TBird 5.0
    88 Ranger 2.3t
    http://vb.foureyedpride.com/showthre...83-Tbird-build

  3. #3

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    You've already experienced one of the traps guys fall into when tuning based off an oxygen sensor. You said it goes lean then misfires. The issue isn't a lean mixture, and richening it up won't fix it. The issue is the misfire. If the fuel doesn't burn then the oxygen isn't depleted and the air fuel gauge thinks it's lean.

    Ford put all the heat riser stuff on these engines for a very good reason, to prevent misfire in a cold engine. Way back when, I learned that lesson the hard way with a little 289. I blocked off the heat riser passage in the intake because that was supposed to free up some horsepower. I didn't notice any more horsepower but it certainly made it bog and spit back when the engine was cold. After a few weeks of that, I pulled the intake again and opened up the heat riser passage.

    The stock dual snorkel air cleaner is a brilliant design and doesn't cost you any power. In fact you will probably make more power since it pulls in cold air from outside the engine bay once the engine warms up. So you get better cold running from the hot air ducts and better warm running as well. It's win-win. If I were you, I'd start with the air cleaner. If you still have issues then also swap to a non-air gap intake.

    You can fiddle fart with the mixture all day long but if the gasoline is too cold to vaporize then it won't matter how much or how little you put in there. Gasoline does not burn, gasoline VAPOR burns.

  4. #4
    FEP Power Member xctasy's Avatar
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    Dunedin 9011, New Zealand, South Pacific
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    Default

    The Street Avenger is a mass produced carb that when set up right gives a great result. Would I use it? Yes, if the price is right.

    http://vb.foureyedpride.com/showthre...rk-plugs-(long

    Spark plugs are not something to save on...

    Sadly some of Saturn V's post on the real time Wide Band and vac readings of an 84 5.0 4180C holley 4-bbl have droped off the 'net.

    A farily full discussion on EGR, the aftermarket frontal labotomy carbs, and some other posts to elaborate. Basically, Ford REALLY knew what it was doing with the 5.0's 460 truck carb and intake, but the Engineers also customised it with even though they kept the truck style dual stage power valve, and all the bowel vents. It got four corner idle stuff to make it pass the emissions test. Very good set up, but past 325 hp, it needs more air flow and is best with mechanical secondaries and if Ford had wanted to, they would have moved to the Carter Thermoquad and run a spreadbore intake manifold, TPS, and a Vapor Vent system to reduce fuel pressure like they did on the 7200 Variable Venturi carb cars.

    But EFI was a real economy, emissions, and service reduction cost, and carbs are very labor intensive. Silicon valley electronics remove a lot of the parts on parts systems, and are like comparing a jet engine to a turbo prop. I think the Vulcan 3.0 Taurus and Mustang 5.0 EFI saved Fords bacon for 1986....

    http://vb.foureyedpride.com/showthre...180-AFR-tuning

    Quote Originally Posted by Saturn V View Post
    This carb came on the car when I bought it 3 years ago, but I think it needs a rebuild for the following reasons.

    • The engine has always been a little hard to start when cold. I have to dry crank the engine for about 10 seconds and then pump the throttle 5-8 times to get it to start when cold. And it actually seems to be worse since replacing the fuel pump and adjusting the idle mixture.
    • The AFR is really rich (10.8:1) at full throttle.
    • After the new intake installation, I pulled the carb and noticed that the carb base gasket was getting soaked with fuel.

    Im having problems with the clamp-on tach input for the Innovate LM-2. I think the clamp got a little too close to the exhaust manifold and melted a little. Now it doesnt consistently measure RPM. So Im going to refer to a trend that I recorded a couple of months ago, before the new Performer 302 intake installation, new fuel pump, and idle mixture adjustment. However, I havent seen any big difference in AFR trends at full throttle after these steps. The purple trend is air fuel ratio (AFR) and the black trend is engine speed.

    • Why the sudden lean spike in the middle of first gear at full throttle?
    • Why the double lean spike at each shift? I know the throttle is closing, but am curious about the double spike.
    • What could cause the AFR to be so rich at full throttle? It gets as low as a bout 10.8:1 in first gear. Could the o-rings in the accelerator pump transfer tube be leaking? I assume the primary jets are original, as well as the secondary metering plate. Ill find out soon when I rebuild the carb.



    As for air cleaners, peak cfm flow from Fords 460 dual snrokle intake exceeds 535 cfm at 25" H20. Enough for a vac sec 4180c carb rated at 630 cfm by other tests. Vac sec carbs only open up enough to meet air flow needs.

    A 780 cfm might need a better internal air filter and better, smoother ducting to the air cleaner, but the race car guys got 390 hp with it, so that puts it up past 625 cfm with more attention to air flow.

    Details here:-


    the 17" external 460 Truck / CFI/4BBL 4V 83-85 3" dual snokle air cleaner flows 535 cfm at the operating pressure drop.

    It has a 14 inch element, up 1 inch on the taller 15 " external 82 2V GT's dual inlet housing.

    The Ram Air Box by apparently flows a claimed 916 cfm, but it is a lot taller with a 4" tall element inside.

    Figures are: http://www.ramairbox.com/flowtest.html




    see http://www.ramairbox.com/models.html


    Others have a 180 degree inlet angle. the above, 135 degrees.

    http://vb.foureyedpride.com/showthre...el-Air-Cleaner

    blue beast's



    Guest 1985CapriGS




    jaz50's
    Quote Originally Posted by Mr Joshua View Post
    you mean this?
    Emile's Mustang.



    Oh, and BMW Rider's re-use of the basic Guest 1985CapriGS air cleaner, the
    Spectre air cleaner assembly.


    Quote Originally Posted by BMW Rider View Post
    Got a call this morning and my Spectre air cleaner was finally in. I'd ordered it back in early November, but it was on back-order. Thanks to Darran (82GTforME) I scored the two air tubes that fit under the fender to draw the cold air up in trade for my fender liners. The air cleaner has flanges that mounted to the skirts in the engine compartment and flex tubes to connect to the air cleaner. It's kind of like an aftermarket version of the HO dual snorkel air cleaner. I did have to add an extension ring to the base to raise it up high enough off the MSD EFI throttle body. That was a fairly simple job to cut a strip of tin form it into a ring and weld it up. The right tube just barely tucks under the MM strut brace, but it looks pretty good I think. The EFI cam with a nice decal that I applied to the lid. I'm not usually one to put decals on anything other than my toolbox, but I liked the way this one looked. Kind of like those sixties muscle cars. Also grabbed a nice Ford logo wing nut to hold it on.


  5. #5

    Default

    Thanks for the replies.

    deathbypsi,
    I'm running a parts store stock-replacement fuel pump, no external regulator. Reading pressure from an inline gauge. As for the vacuum, unless there's something wrong with it, that's what my gauge reads. I have another gauge I can check it against, maybe I should for good measure.

    mrriggs,
    So, if I'm understanding correctly, the misfire is simply from the cold carb not atomizing the fuel. Didn't think about that, makes sense.

    xctasy,
    Thanks for the links and air cleaner info. Will be doing some reading today.


    I'll start with the air cleaner. Went ahead and pulled it off the shelf last night to check it over. Needs a vacuum motor replaced and my original flexible duct sections are disintegrating.

    Thanks guys, trying to learn.
    Last edited by 85MUSTANGTGT; 04-25-2017 at 10:45 AM.

  6. #6

    Default

    What kind of outside temps are we talking here?
    84 Cougar, 88 HO with 700DP, Edelbrock RPM intake, 1.7 RRs, shorty's and SS exh, T-5, KC clutch, Hurst pro billet, line loc, 8.8, 4.10s, suspension mods....blah, blah,blah.

    71 Comet, 289, Liberty TL, 9", 6.00s, 11.9x @ 112.... blah, blah, blah.

  7. #7
    84 Cougar, 88 HO with 700DP, Edelbrock RPM intake, 1.7 RRs, shorty's and SS exh, T-5, KC clutch, Hurst pro billet, line loc, 8.8, 4.10s, suspension mods....blah, blah,blah.

    71 Comet, 289, Liberty TL, 9", 6.00s, 11.9x @ 112.... blah, blah, blah.

  8. #8

    Default

    Carbed engines tend to be "cold blooded". They don't particularly love to run well when they are cold. The colder the air, the worse it gets. The reason is that atomized fuel mixed with cold air results in liquid fuel and fuel-less air.

    This is why engines -- especially those with high rise intakes -- don't run particularly well when they are cold. Bolt a throttle body injection (TBI) based EFI system on to an engine and it helps, but you still run into the same atomization challenges.

    I had a Offenhauser 360 degree manifold sitting on top of my D0OE fulie head 351W years ago and was my daily driver. It would habitually pop out the carb the moment I tried to step on the gas almost regardless of how the choke was set whenever it was cold, yet it would literally dump raw fuel out the exhaust when it was below zero outside. Drove me NUTS - lesson learned about long runner intakes on daily driver cars!

    Not all carbs are created equal in this situation either. The Holley 650 double-pumper I had on it along with the 600 CFM vacuum secondary with two-state power value 4-barrels I had were both miserable on this motor. It would pop power valves almost daily when it would pop out the carb and it started more than its share of paper airfilters on fire too.

    I went to a Carter which had a lower profile and let me switch back to the snorkle air cleaner and add back the heat riser. I also a heater hose based water heater so I could "plug in" my car. Upon startup I would also run a DC heat wrap made for keeping waterlines on campers from freezing and used it to pre-heat my fuel. I also made a get-up to put a 12V bulb under the front fuel bowl on my carb -- again to preheat the fuel.

    There are electronic chokes available with different 'heat up" time delays. Those can work OK in many instance with enough patience. For me I got it to the point that I went to a manual choke. Then I could manage to drive the car without destroying a power valve or lighting the aircleaner on fire every day.

    There is some science behind why everyone went to port EFI or direct injection. You don't have to fight with fuel going back to liquid and running out the tail pipe on you.

    I did put spark plugs in my exhaust near the tips on a coil that I setup to fire the plugs rapidly. Made for some pretty cool fire shows when it was cold or whenever I'd drop the 4 barrel open while I had in bigger jets than the it than it needed.

  9. #9

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    quickshift,
    Temps here lately have been in the 60-80 deg F range. Usually won't drive my car when its much colder than that, but will occasionally drive when its warmer (90+ deg F). Thanks for the tuning article, not sure I've read that one. Looks to be a good one.

    erratic50,
    Thanks for the info.

    Zap's thread on spark plugs that xctasy provided is interesting. Always considered Autolite to be a decent brand. I've been running the AFR-recommended 3924's gapped at .045" since building the engine. It's seemed to run acceptably with these, but will see about picking up something different to experiment with in the future.
    Last edited by 85MUSTANGTGT; 04-25-2017 at 11:09 PM.

  10. #10

    Default

    I run an Eddy RPM with the exh crossover blocked off, a 700DP with an extensive tune and re-curved Duraspark. It took a lot to gt this tune perfect with most success coming from the re-curve after the carb was dialed in. I can run this combo on 45 + days with no problem after a short warm up.Name:  tmp_5049-phone pics 159-1270250489.jpg
Views: 273
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    84 Cougar, 88 HO with 700DP, Edelbrock RPM intake, 1.7 RRs, shorty's and SS exh, T-5, KC clutch, Hurst pro billet, line loc, 8.8, 4.10s, suspension mods....blah, blah,blah.

    71 Comet, 289, Liberty TL, 9", 6.00s, 11.9x @ 112.... blah, blah, blah.

  11. #11

    Default

    After reading your combo more closely, I noticed that you are running a SA670. The last time I called Holley Technical support on another issue, I asked him about the SA series as I had heard they were a tuners nightmare. He said " I wish that carb would go away ". Apparently, their new Brawler series shows potential as being easier to tune. I hope to convince one of my friends to buy one and let me tune it on their car. Me personally, I swear by DPs.
    84 Cougar, 88 HO with 700DP, Edelbrock RPM intake, 1.7 RRs, shorty's and SS exh, T-5, KC clutch, Hurst pro billet, line loc, 8.8, 4.10s, suspension mods....blah, blah,blah.

    71 Comet, 289, Liberty TL, 9", 6.00s, 11.9x @ 112.... blah, blah, blah.

  12. #12

    Default

    Thanks quickshift.

    I've considered ditching this carb, but don't quite have the funds to get something else at the moment. I guess if I keep fooling around with this one I ought to be a pretty good carb tuner by the time I'm done.

  13. #13

    Default

    IMHO, your primary IFRs are too small, and primary IABs are too big (though I'm surprised your idle mixture screws are only 5/8-turn out, (could be a function of secondary idle open a tad too much, getting more idle fuel than necessary from the secondaries. That is a mild camshaft in a 347, so you may need little to very little idle airflow happening through the secondaries) but never mind that for now). That combination is showing you "stupid lean" upon low speed transition, leaving a "hole" between the top of the idle/transition circuit and the start of the main circuit, hence the surging/misfiring. That's a good thing though, because now you know where it is (or quite likely went past). I would put 0.026's back in for the primary IFRs, readjust the idle mixture screws, and see how it acts just with that one change (one change at a time is better than a buncha changes). .... and then I'd reduce the size of the primary IABs (I would guess 0.073", but nothing's in stone. I'd reduce what you're running a couple thou at a time) until you're still getting good lean progression upon light acceleration, but so that the car isn't bitching but getting what it wants. You'll know when you've found the sweet spot because there will be lean progression hand-in-hand with effortless and brisk acceleration.

    After the sweet spot is found for what it wants for transition, you should be able to reduce the primary main jet size back to 65 (or less, again, based on what the car tells you upon acceleration above ~2500rpm, where the main circuit does it's job), but be sure to address WOT and increase those PVCRs lastly with a very careful and close eye on your WB.

    It's better than normal, but best function to progress lean (sometimes 18+:1 is absolutely possible) upon low speed transition acceleration (which is entirely the job of the idle and transition circuits) below the point of the main circuit and/or above the vacuum level of the power valve PVCRs taking over.

    Additionally, when running right, an engine could care less what kind of (or if an) air filter is on it. The amount the choke blade opens can have a large affect on how something runs and warms as well as how well it's "cold drive-ability" is, which is solely a matter of being rich enough for that/those modes of function.
    Last edited by Walking-Tall; 04-26-2017 at 03:23 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

  14. #14

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    Thanks Walking-Tall,
    I'll try changing the IAB's and report back. It may be a be a day or two though, have rain forecasted for most of the remainder of the week. Believe I already have some .073 bleeds already drilled.

  15. #15

    Default

    You're welcome, Thomas. It's just Mike.

    Common good baseline starting or "universal" calibration for that carburetor, which is 600cfm (1-9/16" throttle bores and 1-1/4" primary & 1-5/16" secondary venturi) actual and 70cfm marketing, the same throttle bore and venturi dimensions as a good 'ole LIST-1850 600cfm, is 0.026" PIFRs, 0.073" PIABs, somewhere in the neighborhood of #66 primary jets, and 0.046" PVCRs. When you were in there, how many emulsion bleeds are in the primary metering block, and did you measure them? What's the secondary block? Did it come with the carburetor? Also, where are the primary IFRs located, down low or up high? Location doesn't make a huge difference with your mild camshaft, but it can have an rpm-dependent AFR affect. AFR should be load-dependent, not rpm-dependent. Down low = good, up high = bad... because, up high, especially with enough camshaft duration/overlap, air can get behind the IFR and wreak havoc with idle/transition function...

    It's rainy here right now too. Luckily I was able to finish up with a '74 Pontiac LeMans over the weekend. It's Rochester 2-barrel was in bad need of rebuild (filter way past due to be changed, dirt in the float bowl, etc...), and it's (points & condenser) ignition tuned up. Just thinking about you saying how yours acts when cold. This car was not cooperating at all when cold. Long story, short, the choke blade was being opened by the vacuum pull-off what I thought was too much, and was about three times as much as was even listed as the spec in the rebuild kit's instructions. I got an email Monday morning about how great the car ran and that it worked like a new car. So stick with it and you'll get it working great.
    Last edited by Walking-Tall; 04-26-2017 at 05:37 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

  16. #16

    Default

    Quote Originally Posted by erratic50 View Post
    Carbed engines tend to be "cold blooded". They don't particularly love to run well when they are cold. The colder the air, the worse it gets. The reason is that atomized fuel mixed with cold air results in liquid fuel and fuel-less air.

    I had a Offenhauser 360 degree manifold sitting on top of my D0OE fulie head 351W years ago and was my daily driver. It would habitually pop out the carb the moment I tried to step on the gas almost regardless of how the choke was set whenever it was cold, yet it would literally dump raw fuel out the exhaust when it was below zero outside. Drove me NUTS - lesson learned about long runner intakes on daily driver cars!

    Not all carbs are created equal in this situation either. The Holley 650 double-pumper I had on it along with the 600 CFM vacuum secondary with two-state power value 4-barrels I had were both miserable on this motor. It would pop power valves almost daily when it would pop out the carb and it started more than its share of paper airfilters on fire too.

    There is some science behind why everyone went to port EFI or direct injection. You don't have to fight with fuel going back to liquid and running out the tail pipe on you.

    I did put spark plugs in my exhaust near the tips on a coil that I setup to fire the plugs rapidly. Made for some pretty cool fire shows when it was cold or whenever I'd drop the 4 barrel open while I had in bigger jets than the it than it needed.
    If they are dialed in right, there's no problem at all. The ONLY unavoidable problem that crops up is "carb icing" with dampness/cold.

    Popping out the carburetor and/or popping power valves (a BS myth snowballed over decades now) has everything to do with being too lean.

    There's no science at all, besides forcing an engine to do that which it would never do on it's own efficiently.

    The three ring circus fire show does nothing but verify a rich mixture.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

  17. #17

    Default

    Thanks Mike. Really appreciate the help.

    Attached are pics of the metering blocks. They are original to the carb. IFR's at bottom of well.
    Has 12319 stamped on side. Upper hole: #61 drill size, .039" Lower hole: #71, .029"



    Has 11075 stamped on top. Two holes each well, all #44, .086". No holes in upper section of well.

    Last edited by 85MUSTANGTGT; 07-08-2017 at 09:38 PM. Reason: fix photos

  18. #18

    Default

    Mike - yea, lean mixture scenarios can be endless and annoying in cold weather. Raw fuel dumping out the pipe while the air mix is - like you said - lean.

    The old timers born in the early 1900's talked about adding metal screen to the air inlet tract so if fuel did go back to liquid there was a better chance of re-atomizing. Of course they were working on Model A's with flathead V8s - a very different motor from those that came after.

    Odd theory - but I know it works because I added a spacer and a screen to my W as a last ditch effort to make it run half way decent in below zero temps while cold.

  19. #19

    Default

    Quote Originally Posted by 85MUSTANGTGT View Post
    Thanks Mike. Really appreciate the help.

    Attached are pics of the metering blocks. They are original to the carb. IFR's at bottom of well.
    Has 12319 stamped on side. Upper hole: #61 drill size, .039" Lower hole: #71, .029"


    Has 11075 stamped on top. Two holes each well, all #44, .086". No holes in upper section of well.
    IFRs down low, good. The 0.029" kill bleeds probably explains the original calibration with 0.055" PVCRs, where normally 0.046" PVCRs get the job done. Not that 0.055" is going to be necessary for your combination. You and your WB will find out what primary PVCRs are necessary for ~12.5:1 WOT AFR, after you've got the most efficient size primary jets in it for part throttle acceleration that's deeper into the throttle prior to PVCR enrichment.

    Regarding the 4 emulsion bleeds in the secondary block: if you look with a light and reach in further/deeper, you should see and measure emulsion bleed restrictions of about 0.028" each, about 1/4" down in the holes. If they are actually 0.086" right into the main wells, somebody's done that with a drill bit, and that's FAR too much "emulsion". A situation like that, a metering block that's been butchered like that, can be repaired by drilling and tapping the 4 of them for 4-40, 6-32, or even 8-32 if necessary, and brass restrictions drilled with 0.028" installed.
    Last edited by Walking-Tall; 04-27-2017 at 04:07 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

  20. #20

    Default

    Quote Originally Posted by erratic50 View Post
    Mike - yea, lean mixture scenarios can be endless and annoying in cold weather. Raw fuel dumping out the pipe while the air mix is - like you said - lean.

    The old timers born in the early 1900's talked about adding metal screen to the air inlet tract so if fuel did go back to liquid there was a better chance of re-atomizing. Of course they were working on Model A's with flathead V8s - a very different motor from those that came after.

    Odd theory - but I know it works because I added a spacer and a screen to my W as a last ditch effort to make it run half way decent in below zero temps while cold.
    Horse feathers, they're all air pumps. Problems arise in the cold when intakes don't get heated up much, like when blocking heat risers, or no doubt with air gap manifolds, but finding what an engine wants just takes a bit of fiddling, and then it's really rewarding how well they function.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

  21. #21

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    For the record, I bought this carb new from Summit about 10 years ago. So, until about a year or so ago, it was as it came from Holley - that is unless it was a return that Summit resold. Nobody has touched it other than me that I am aware of.

    I'll re-measure those secondary emulsion bleeds tonight after work and report back. I knew those seemed huge, but didn't think to investigate further.

    Looks like we may get a break in the weather here today, will see about making those IFR/IAB changes and go for a drive if time permits.

    Thanks for the help Mike.

  22. #22

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    You're quite welcome.

    Further thoughts with your primary block:
    Up top of it, are there 2 cup plugs and 2 flat plugs, like this:



    ... or all 4 cup plugs? Because... working in conjunction with those upper bleeds that you measured to be 0.039", are usually brass IFR/emulsion tubes in the main wells. If this is the case, there may be angle channels drilled over to the main wells at the very top of the (visible) long vertical idle channels that lead directly to the transfer slots in the base plate, and fuel is sent tailored outward with the mixture screws for the idle constant feed holes. Personally, I'm not a fan of blocks like this, because there's an unknown size restriction variable of IFR and maybe some horizontally-drilled "emulsion" holes in the brass tube inserts. Unless you can very carefully remove, measure, and replace them, there's no knowing what size restriction is in there, what height the end restriction is at, as well as no easy way of changing what size restriction is at the ends of those tubes. I picked up the block you see above to modify, that's likely headed onto the front of a LIST-3310 I'm getting together. It had no down-low IFRs and had brass tube restrictions into the main wells. I tapped it 6-32 for low position IFRs where there were none, removed the main well tubes with central drilling and screw inserting and pulling them out, blocked the uppermost bleeds like with yours with epoxy, tapped PVCRs 8-32, and will install new 1/4" brass cup plugs at all 4 locations up top, with inner main well cup plugs as deep down as necessary at about the same level where the blocked bleeds are. Just something to keep in mind, where your reducing the size of the accessible lower IFRs (or did you add those where there were none?) may or may not have a large affect on mixture screw or transition behavior. Though, you should be able to gauge and better dial-in what's going on with changing the PIABs in small steps.

    Good luck with it, and keep us posted.
    Last edited by Walking-Tall; 04-27-2017 at 03:42 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

  23. #23

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    Mike, you were right on the secondary emulsion bleeds, they are .028 (maybe closer to .027) as measured by my # drills.

    Primary block - right, Secondary block - left



    All holes that I've drilled/tapped had pressed-in brass restrictors/bleeds, except for the PCVR's, they were just a drilled hole.
    Last edited by 85MUSTANGTGT; 07-08-2017 at 09:40 PM.

  24. #24

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    A wonky manufacturing/assembly issue I've seen frequent mention of with (even right out of the box) Street Avengers are that the passages that the primary mixture needle tips go into were far too big, at over 0.100". They shouldn't be much bigger than 0.063". Those passages too big causes the minimal-turns-out situation.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

  25. #25

    Default

    Quote Originally Posted by 85MUSTANGTGT View Post
    Mike, you were right on the secondary emulsion bleeds, they are .028 (maybe closer to .027) as measured by my # drills.

    Primary block - right, Secondary block - left


    All holes that I've drilled/tapped had pressed-in brass restrictors/bleeds, except for the PCVR's, they were just a drilled hole.
    Cool. You had me scared for a second there with the 0.086" holes , lol

    Alright, it's got emulsion tubes in the primary block. Either in the ends of those, or in restrictions under the idle well cup plugs, are what ultimately dictates how much air:fuel gets to the idle/transition circuits, unless a smaller restriction down low smaller than them chokes things off... which is what I'm guessing is happening, in conjunction with a too-big PIAB...
    Last edited by Walking-Tall; 04-27-2017 at 06:00 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1966 Ford Fairlane sedan
    1966 Ford Fairlane GT
    1981 Mercury Marquis Brougham
    1980 Capri RS Turbo
    1971 Mustang
    1974 Pontiac LeMans

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