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  1. #1

    Default Carb/Ignition Timing Adjustment Questions?

    Hey guys. I have a 1985 GT that is running pretty rich. Everything on the car is stock except the flowmaster exhaust and the Holley 3150 carb, both of which were done by the previous owner. I realize that the carb may be a little big for the stock 302 (I believe it is a 750cfm) but getting a new carb is not in the cards right now.

    Currently I have the carb leaned out as much as possible (I believe). I adjusted the screws on each side with the car off to 1.5 turns open, then turned them in 1/8th of a turn at a time alternating sides until I noticed a change in the way it was running, then backed the screws back 1/8th. Is this the correct thing to do? Any tips/suggestions?

    I also replaced the plugs, distributor cap, and rotor (parts store didn't have new wires in stock) last night. While doing this I discovered that the previous owner had the distributor 180 degrees out. I put the engine at TDC and turned the distributor so that the rotor is facing #1 on the cap and set the timing with a timing light at 10 degrees with the vacuum advance plugged. Any recommendations for timing besides the stock numbers for a little more efficiency/power? I don't want to tear up this motor. It's only got 44000 miles on it.

    My goal is for this car to run pretty much stock for right now. Thanks in advance for your help.

    Carl

  2. #2

    Default

    See if you can trade the 750 for a 600 - more is always better, right?

    750 is too much for a stock 302.
    '88 Mustang GT convertible, T5, 3.08:1 gears. 5.0 Explobra Jet: A9L Mass Air conversion, Fenderwell Mac cold air intake, 70mm MAF meter = 4.6 T-Bird/Cougar housing + '95 Mustang F2VF-12B579-A1A sensor, aftermarket 70mm throttle body and spacer, Explorer intakes, GT40P heads with Alex's Parts springs and drilled for thermactor, Crane F3ZE-6529-AB 1.7 "Cobra" roller rockers, Ford Racing P50 headers, Mac H-pipe, Magnaflow catback, Walbro 190 LPH fuel pump, UPR firewall adjuster and quadrant with Ford OEM cable, 3G conversion ('95 Mustang V6), Taurus fan, rolled on Rustoleum gloss white paint...
    Past Four Eyes: Red well optioned '82 GT 5.0, Black T-top '81 Capri Black Magic 3.3L 4 speed, Black T-top '84 Capri RS 5.0 5 speed.Over 200,000 miles driven in Four Eyes, and over 350,000 in Fox Body cars.

  3. #3
    FEP Super Member FM2NOTCH's Avatar
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    Default

    sounds like you tuned it right,you might check total timing(vacuum advance plugged) my 85 runs best at 36 degrees total, all in by around 3000 rpm, or just bump the intial timing up a couple degrees at a time and see how it reacts. you need to lose the 750, it should run much better with a 600-650 holley
    Last edited by FM2NOTCH; 10-11-2013 at 06:24 AM.
    *FOXTOBERFEST* 2015 http://www.foxmustangrestoration.com/events
    85 T Top coupe 5.0 2R red, E7's, rpm intake, 4180 carb, 7.4 1/8
    83 CC capri 5.0 5 speed,black mesh wheels
    76 cobra II 302 auto black/gold, big cam 3 inch dumps- sold to a good friend
    92 coupe 5.0 5 speed -red
    92 Lx hatch 5.0 5 speed -black, 66 coupe 5.0 4 spd (project)
    87 Vert 5.0 AOD red stock as a rock

    " Are you sure you know what you're talking about? It kinda sounds like you know what you're talking about"

  4. #4
    FEP Super Member bwguardian's Avatar
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    As stated above the carb is too big. More importantly though is what the previous owner did with the smog equipment that hooked up to the stock 4180c carb.
    HAD
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  5. #5

    Default

    Thanks guys. I'm in the process of trying to find a stock 4180c for my car. I'm going to try to sale/trade the holley 3150 that's on there since I have no use for it.

    As for the smog equipment, all of it is still there and hooked up minus a hose laying around the back side of the motor that I'm assuming hooks up to the stock carb. I couldn't find anywhere else for it to hook up.

  6. #6
    FEP Super Member FM2NOTCH's Avatar
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    4180 is a good carb with some work,but they use special gaskets, etc. I'd find a good old 600 vacuum secondary ,then get a adjustable secondary kit, and add a metering block kit on the rear so you can change the jets.
    *FOXTOBERFEST* 2015 http://www.foxmustangrestoration.com/events
    85 T Top coupe 5.0 2R red, E7's, rpm intake, 4180 carb, 7.4 1/8
    83 CC capri 5.0 5 speed,black mesh wheels
    76 cobra II 302 auto black/gold, big cam 3 inch dumps- sold to a good friend
    92 coupe 5.0 5 speed -red
    92 Lx hatch 5.0 5 speed -black, 66 coupe 5.0 4 spd (project)
    87 Vert 5.0 AOD red stock as a rock

    " Are you sure you know what you're talking about? It kinda sounds like you know what you're talking about"

  7. #7

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    Quote Originally Posted by carlwcaglejr View Post
    As for the smog equipment, all of it is still there and hooked up minus a hose laying around the back side of the motor that I'm assuming hooks up to the stock carb.
    If there's an identical hose at the front, it's for the vapor purge/canister purge system. They route fumes from the canister to the carb bowls - or vice-versa.
    '88 Mustang GT convertible, T5, 3.08:1 gears. 5.0 Explobra Jet: A9L Mass Air conversion, Fenderwell Mac cold air intake, 70mm MAF meter = 4.6 T-Bird/Cougar housing + '95 Mustang F2VF-12B579-A1A sensor, aftermarket 70mm throttle body and spacer, Explorer intakes, GT40P heads with Alex's Parts springs and drilled for thermactor, Crane F3ZE-6529-AB 1.7 "Cobra" roller rockers, Ford Racing P50 headers, Mac H-pipe, Magnaflow catback, Walbro 190 LPH fuel pump, UPR firewall adjuster and quadrant with Ford OEM cable, 3G conversion ('95 Mustang V6), Taurus fan, rolled on Rustoleum gloss white paint...
    Past Four Eyes: Red well optioned '82 GT 5.0, Black T-top '81 Capri Black Magic 3.3L 4 speed, Black T-top '84 Capri RS 5.0 5 speed.Over 200,000 miles driven in Four Eyes, and over 350,000 in Fox Body cars.

  8. #8

    Default

    Thanks for your input, guys. I hope I can get another carb soon and I have another question.

    On the engine, what are the two connections on the back, driver side of the intake manifold? One is electrical (gray and red), the other looks like vacuum connections (green). These are not connected in my car and have actually been cut off/removed by the previous owner.

    Thanks.

  9. #9

    Default

    That rear driver side of the intake has a couple of Temperature Controlled Vacuum switches, at least one of which, threads into the coolant passage. They regulate vacuum to emissions equipment, and IIRC, the ported vacuum from the carb to the vacuum advance on the distributor. My '82 and '84 each had two of them. I think some are green, some are light blue, and some are orange. If you still have the VECI (emissions) sticker under your hood, I think that it shows those things in their appropriate colors, in the vacuum schematic diagram.

    Dunno about the electric. Can you post pics?
    '88 Mustang GT convertible, T5, 3.08:1 gears. 5.0 Explobra Jet: A9L Mass Air conversion, Fenderwell Mac cold air intake, 70mm MAF meter = 4.6 T-Bird/Cougar housing + '95 Mustang F2VF-12B579-A1A sensor, aftermarket 70mm throttle body and spacer, Explorer intakes, GT40P heads with Alex's Parts springs and drilled for thermactor, Crane F3ZE-6529-AB 1.7 "Cobra" roller rockers, Ford Racing P50 headers, Mac H-pipe, Magnaflow catback, Walbro 190 LPH fuel pump, UPR firewall adjuster and quadrant with Ford OEM cable, 3G conversion ('95 Mustang V6), Taurus fan, rolled on Rustoleum gloss white paint...
    Past Four Eyes: Red well optioned '82 GT 5.0, Black T-top '81 Capri Black Magic 3.3L 4 speed, Black T-top '84 Capri RS 5.0 5 speed.Over 200,000 miles driven in Four Eyes, and over 350,000 in Fox Body cars.

  10. #10

    Default

    Quote Originally Posted by FM2NOTCH View Post
    4180 is a good carb with some work,but they use special gaskets, etc. I'd find a good old 600 vacuum secondary ,then get a adjustable secondary kit, and add a metering block kit on the rear so you can change the jets.
    Every gasket you would ever need for a 4180C comes in the Holley 3-1346 kit. Or all of them
    can be bought separately from any place that sells Holley parts. Primary bowl gasket is 108-56,
    primary metering block gasket is 108-55, secondary metering plate paper gasket is 108-13 (the
    big one is the same as 4160) throttle plate gasket is 108-57. Accelerator pump transfer tube
    o-rings are 26-38.

    And apart from a good rebuild using the right kit, a 121-131 squirter, and some #63 primary jets
    if they oxygenate the fuel where you live, there really isn't anything else a Mustang 4180C needs.
    Ford got those carbs pretty close to perfect for our cars. I know some guys like to put the 4150
    style secondary metering block on, but after much experimentation on mine, I have actually come
    full circle, back to the original metering plate.

    Quote Originally Posted by carlwcaglejr View Post
    On the engine, what are the two connections on the back, driver side of the intake manifold? One is electrical (gray and red), the other looks like vacuum connections (green). These are not connected in my car and have actually been cut off/removed by the previous owner.
    These are thermal vacuum switches. The one with the electrical connector is for the vacuum advance.
    When the engine is cold, the vacuum advance is fed manifold vacuum, to aid idle when the engine is
    still cold, but the choke has opened. Once the engine is warmed up, the vacuum advance switches
    over to ported vacuum. The electrical switch is used by the shift light circuit, to inhibit the light when
    the engine is cold.

    The second thermal vacuum switch is for EGR vacuum. When the engine is cold, EGR vacuum is routed
    to the flapper valve, through a check valve with a release port. When the engine is warmed up, the EGR
    vacuum switches over to supply the EGR valve, Evap canister purge valves, TAD solenoid, and the release
    port on the flapper check valve.

    On both valves, the vacuum source goes to the center port. The vacuum will be present on the bottom
    port when the valve is cold, and the top port once the valve has reached it's switch-over temperature.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  11. #11
    FEP Super Member FM2NOTCH's Avatar
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    most chain store auto parts will have regular 4160 holley 600 gaskets,kits,parts but not so much for the 4180 and rebuild kits for the 4160 usually cost less.
    Last edited by FM2NOTCH; 10-12-2013 at 05:39 AM.
    *FOXTOBERFEST* 2015 http://www.foxmustangrestoration.com/events
    85 T Top coupe 5.0 2R red, E7's, rpm intake, 4180 carb, 7.4 1/8
    83 CC capri 5.0 5 speed,black mesh wheels
    76 cobra II 302 auto black/gold, big cam 3 inch dumps- sold to a good friend
    92 coupe 5.0 5 speed -red
    92 Lx hatch 5.0 5 speed -black, 66 coupe 5.0 4 spd (project)
    87 Vert 5.0 AOD red stock as a rock

    " Are you sure you know what you're talking about? It kinda sounds like you know what you're talking about"

  12. #12

    Default

    Thanks everyone. I've been thinking about buying a Holley 4160 (80457) and have read about some fitment issues due to the EGR valve. Can you shed any light on this? Is this really an issue?

    I don't want to have any hiccups if I go spend $300-$400 on a new carb.

    Thanks.

    Carl

  13. #13

    Default

    If that holley is a regular old vacuum-secondary, non center-hung-float bowl, carburetor, then it should still fit fine, except for the inlet location for the fuel line.
    I ran one on my '84 while the original was being fixed, and it fit fine - even with some rubber hose used to temporarily connect the factory line to the inlet. I'm pretty darn sure that the heat shield fits as well. The larger diameter '84-'85 air filter assembly fits too, IIRC, whereas I had to make a spacer to run that 4160 under my old '82 GTs air filter.
    '88 Mustang GT convertible, T5, 3.08:1 gears. 5.0 Explobra Jet: A9L Mass Air conversion, Fenderwell Mac cold air intake, 70mm MAF meter = 4.6 T-Bird/Cougar housing + '95 Mustang F2VF-12B579-A1A sensor, aftermarket 70mm throttle body and spacer, Explorer intakes, GT40P heads with Alex's Parts springs and drilled for thermactor, Crane F3ZE-6529-AB 1.7 "Cobra" roller rockers, Ford Racing P50 headers, Mac H-pipe, Magnaflow catback, Walbro 190 LPH fuel pump, UPR firewall adjuster and quadrant with Ford OEM cable, 3G conversion ('95 Mustang V6), Taurus fan, rolled on Rustoleum gloss white paint...
    Past Four Eyes: Red well optioned '82 GT 5.0, Black T-top '81 Capri Black Magic 3.3L 4 speed, Black T-top '84 Capri RS 5.0 5 speed.Over 200,000 miles driven in Four Eyes, and over 350,000 in Fox Body cars.

  14. #14

    Default

    Does anyone know the correct part numbers for the ported vacuum switches on the rear, driver side of the intake manifold. I was going to buy them, but there are multiple versions available and I want to get the correct ones.

    Thanks.

  15. #15

    Default

    I finally got the carburetor and timing adjusted correctly. Thank you guys for all your help.

    Carl

  16. #16

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    My dad and I also got the tachometer and temperature gage working. Yay! She sure is running good now.

    Carl

  17. #17
    FEP Super Member PaceFever79's Avatar
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    Excellent!

  18. #18
    FEP Power Member horsepowerjunkie's Avatar
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    What is the list number off of the front of the choke housing on your existing carb?
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  19. #19

    Default

    The numbers on the carb are:
    80457-9
    3150

    I have her running pretty good now that I got some time off to spend working on her. In my original post on this thread, I had incorrectly determined this carb to be a 750 cfm carb. I guess I typed in a wrong number or something. She seems to be pretty dialed in now though. Turns out the accelerator pump was continuously squirting gas into the carb. Once I found that and adjusted it, I was able to do a little more tweaking on the mixture and timing.

    Thanks for all the help and time. I love this site.

    Carl
    Last edited by carlwcaglejr; 10-27-2013 at 10:03 PM.

  20. #20
    FEP Senior Member BlackMamba's Avatar
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    Quote Originally Posted by carlwcaglejr View Post
    My dad and I also got the tachometer and temperature gage working. Yay! She sure is running good now.

    Carl
    What was the issue with the Tach and Temp?
    After my engine swap(306) in my 84GT both those gauges stopped working.
    Fixed the Tach(burned fuse) but still cant figure out the Temp.
    Current Cars:
    1979 Mustang Ghia Coupe 5.0 3J Bright Blue
    1984 GT T top 306 5 speed "Black Mamba"
    1986 Saleen Black with Silver Stripes 86#009
    1986 Mustang GT Medium Canyon Red 5 speed 5.0
    1999 Mustang GT Convertible 35th anniversary 69K miles.
    2002 Nissan Maxima 6 Speed "Daily Driver"
    2009 Corvette 6 speed LS3

    1998 Cobra 71k miles Canary Yellow "Nana" SOLD

  21. #21

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    The temp gage ended up being a really easy fix. It just turned out to be a faulty sender (front of intake manifold, driver side). I replaced it with a new one from O'Reilly's for about $8 or so. Works great.

  22. #22

    Default

    Alright guys, I have a few more questions now that I've been driving the car with the current adjustments for a while.

    Last week, I replaced the 65 jets in my 600 holley with 62 jets just to see what would happen. I'm only getting about 14 mpg with the 65s. The car didn't run too well because it was too lean. To make it run well with the 62 jets, the timing had to be advanced way too far, ~30 btdc. So, I put the 65 jets back in and adjusted my timing back to 12 btdc per the hood decal.

    That's the background, this is my question. Should I leave the timing where it's at (12 btdc) and keep changing jets until I achieve the best vacuum at that timing?

    I'm just trying to make my car a little better and more efficient. Thanks for the help.
    Carl

    1985 Mustang GT Hatchback (Totaled) :-(
    2007 Mustang GT Premium
    1985 Mustang GT Hatchback
    1965 Mustang

  23. #23

    Default

    Your 65s probably aren't too far off, in a carb with straight-leg boosters. That's only two sizes
    larger than I run in the annular-booster 4180C. You might be able to go a little smaller, but I
    wouldn't expect to get all the way down to 63s without part-throttle surge.

    With your current carburetor, I'd say the best places to go looking for efficiency are going to be
    in the vacuum advance system, and power valve. A vacuum advance system, properly connected
    and functioning, can make a huge difference in part-throttle fuel economy. Have you verified the
    vacuum advance is working?

    Also, if your power valve is opening too soon, that will also reduce efficiency. The old rules of
    thumb for Holley power valves are really just to get you to a starting point. Once you know the
    vacuum advance is working as it should be, you might experiment with numerically lower power
    valves, until you find the point where a flat spot appears under part-throttle acceleration, with
    the manifold vacuum just above the opening point of the valve. You will need to have a vacuum
    gauge rigged up where you can watch it while driving.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  24. #24

    Default

    Ok. As far as I can tell my vacuum advance is working properly and I found out that my carb has a 6.5" power valve when I changed the jets. It currently idles at about 20". Hopefully I can get a 4180c for a 1985 soon or get these efficiency issues worked out.
    Carl

    1985 Mustang GT Hatchback (Totaled) :-(
    2007 Mustang GT Premium
    1985 Mustang GT Hatchback
    1965 Mustang

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