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  1. #151
    FEP Super Member JTurbo's Avatar
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    Jan 2006
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    Western MA
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    Awesome news!
    1979 Indy Pace Car Mustang 302 / 5spd
    1982 Mustang GT T-Top 302 / 4spd
    1986 SVO Mustang - 1C

  2. #152

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    Quote Originally Posted by grabbergreen84 View Post
    That's awesome! More power?
    Not sure on the full power spectrum, no voyage with it yet until everything's buttoned up, but with a quick 1/4 blip of the throttle out on the street, she certainly peeled the wheel easily in an instant, lol
    I'm most happy with how steady and quiet and smooth it's running already before any "super tuning" of the idle circuit and jetting/pvcr's... really, it's running like it should have been running all along.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  3. #153

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    Quote Originally Posted by homer302 View Post
    Looking good! Everything looks to be very professionally installed. I have never seen a Fox without the strut plates on the top of the shock tower before. Keep up the good work.
    Thanks very much.

    You mean caster/camber plates?...
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  4. #154

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    Quote Originally Posted by JTurbo View Post
    Awesome news!
    Thanks!
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  5. #155

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    Drilled out factory idle feed restrictions (Ø0.036"), tapped holes for 6-32 thread, and installed brass socket setscrews with Ø0.031" restrictions. This had a grand total affect of nearly zero, lol... mixture screws are still in the neighborhood of 3/4 turns out. Obviously, a larger reduction is necessary to cause more of an idle mixture screw difference in this case. I'm shooting for 1-1/2 turns out because that's a good indicator that the idle feed restriction's size is ideal for the situation. A further step down to Ø0.025" restrictions is approximately half of the original's Ø0.036" area, so I'll try that next.



    It's a whole different animal now. Made a handful of trips out the highway, and (without pushing it hard at all yet) it's got strong, smooth acceleration with no hiccups/surging/pinging anywhere with 14-degrees BTDC and plain old crap 87-octane. Reduced the vacuum advance about 10-degrees during one of those trips. Stepping down as far as possible with the main jets (with accordingly adjusted PVCR's) soon is next...
    Last edited by Walking-Tall; 07-19-2017 at 11:49 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  6. #156

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    Reduced the IFR's to 0.027", and gained further turns out with mixture screws, and wow is this thing ever running nice. Smooth as glass and effortless rapid acceleration that gets away from you because your foot's barely on the gas and she's zoomin' right along. Changed out the 73 jets for 68's and supplemented PVCR's accordingly with 0.073" restrictions installed, and sped up (backed off the heavy spring's tension) the centrifugal advance a bit. The O2 sensors in the manifolds got put to work today, and their cruise voltage was ~125mV (~15:1 AFR) and no surging. No WOT business yet, that's still comin'. I'm more interested in it running perfectly from idle up through the mid range to the mains, with fueling and timing, and it's damn near there.
    Last edited by Walking-Tall; 08-09-2016 at 07:22 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  7. #157

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    Carburetor calibration as of 08-20-2016:
    - Idle Air Bleeds - Ø0.066"
    - High Speed Air Bleeds - Ø0.027"
    - Idle Feed Restrictions - Ø0.027"
    - Main Kill Bleeds - Ø0.028"
    - Accelerator pump shooter - #31
    - PVCR's (power valve channel restrictions) - Ø0.073" (*0.0042in²)
    - Main Jets - #68 (Ø0.069" - *0.0037in²)
    - * Total fuel flow area for WOT for each throttle bore = 0.0079in²

    Initial timing remains at 14-degrees BTDC, 38-degrees total (initial + centrifugal). It likes those numbers very much. Today I limited the vacuum advance to about half of it's travel because it provided an adjustment window of 16 to 24 additional (crankshaft) degrees of timing advance, both of which are far too much (for anything, IMHO) with an optimized initial timing setting and a mechanical advance curve that works well with this application.

    The starter began making a racket last week. I took it out a couple days ago, which was no small task, the proverbial 10-pound starter through a 5-pound hole. In the area is a catastrophic convertor, the oil pan, the k-member, and the transmission's bell housing. A large bar was necessary to move the whole engine/transmission toward the driver's side, as well as another to wedge/pry the damn starter out of there. I'll be raising the whole works as much as I can to get it back in. Anyway, the starter itself looks to be a recent replacement judging by it's innards. Somebody put an adequate length (musta lost the original) in the top bolt's position, without a lock washer, but a flat washer, and the bolt head's corners were nearly rounded off too. Fool. Brilliant move. This is why it came loose, and also why now the nose bushing and the drive are bitched. So, waiting on those parts before any more important dialing in takes place...

    Also replaced the drive-end bearing in the alternator, because it's been slowly increasing the amount of noise that it started making.
    Last edited by Walking-Tall; 08-20-2016 at 10:15 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  8. #158

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    Regarding this jalopy's electric fuel pump and system for carburetion:

    For reference if not previously mentioned, I am using the following pump:
    http://www.rockauto.com/en/moreinfo....133671&jsn=719

    At first I put a 1/32" restriction into the 1/4-NPT barb that attaches to the return line, that's in my bypass/return contraption (a T, with three 1/4-NPT brass barbs for 5/16" fuel line), and 9-10psi running pressure near the carburetor was the result. I increased the restriction size to 1/16" and the pressure dropped a pound to 8psi. I'll try a 1/8" restriction size next, because somewhere around 5psi is what I'd like to see...

    Even with the smallest return restriction to begin with, the new pump's been quietly, nearly imperceptibly humming away doing it's job. Their stated specifications list less than or equal to 4 amps. A 5 amp fuse is at the beginning of the full power feed wire (14+ volts running measured back there) to the pump's relay, and besides needing to get the pressure lowered, it's all working fine. It's far and away a much quieter running pump than the high pressure CFI pump that was in the car, that by it's numbers, is the 30 year old original.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  9. #159

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    I tip my hat to you for tinkering with the old Essex engine.

    I did the same for 20 odd years but never got a satisfactory amount of power out of it, especially with the C5 transmission.

    I tried lots of things from headers and exhaust to intakes and carbs (Tom Morana stuff or my own brew mostly).

    It was stone axe reliable and I was grateful for that. But power and MPG just plain sucked. Power was only about "on par" with my ex-wife's old 92 FI 4cyl mustang, but at least the 2.3 got better MPG.

    A 5 Speed might be a better match for it if looking to wring every last pony out of it, but it's not very happy at higher rpm either. It is what it is...

    Ultimately, it was still running like a top when I pulled it for a 302 and a T5 this year. Was a little sad driving away when I dropped it off at the scrap yard. It was a faithful old power plant, if not a powerful one.

    Keep digging for power, but I fear you will be ultimately disappointed if looking for anything much more than a rock solid driver with maybe just a scootch more power than needed to get out of it's own way.

    Nice find on the GM module. I've never seen that one before. My Durasparks have always been rock solid for me, never had one fail. So I've have never had to fish around for an alternative.

    Good luck on your journey.

    Last edited by great white; 08-21-2016 at 08:24 AM.

  10. #160

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    Quote Originally Posted by great white View Post
    I tip my hat to you for tinkering with the old Essex engine.

    I did the same for 20 odd years but never got a satisfactory amount of power out of it, especially with the C5 transmission.

    I tried lots of things from headers and exhaust to intakes and carbs (Tom Morana stuff or my own brew mostly).

    It was stone axe reliable and I was grateful for that. But power and MPG just plain sucked. Power was only about "on par" with my ex-wife's old 92 FI 4cyl mustang, but at least the 2.3 got better MPG.

    A 5 Speed might be a better match for it if looking to wring every last pony out of it, but it's not very happy at higher rpm either. It is what it is...

    Ultimately, it was still running like a top when I pulled it for a 302 and a T5 this year. Was a little sad driving away when I dropped it off at the scrap yard. It was a faithful old power plant, if not a powerful one.

    Keep digging for power, but I fear you will be ultimately disappointed if looking for anything much more than a rock solid driver with maybe just a scootch more power than needed to get out of it's own way.

    Nice find on the GM module. I've never seen that one before. My Durasparks have always been rock solid for me, never had one fail. So I've have never had to fish around for an alternative.

    Good luck on your journey.

    I'm not expecting great gobs of power, but with the efficiency tuning done so far, power increase has gone hand-in-hand with it, and I know there's still more in it, because I'm not finished dialing it in. Most important to me with this though is dead-nuts reliable and consistent good running, and maximizing fuel efficiency. It was an absolute pig during a (babied) 24 hour trek, using roughly nearly twice the gas I had conservatively estimated, and had been just as much or worse of a pig bombing around town while still stifled with CFI, and there's absolutely no reason or excuse for that IMHO.

    I've been out the highway and up to highway speed with it a couple times so far, and she hums right along barely tickling the accelerator. I trounced on it once, it downshifted to 2nd and roared to life and ran up the tach like never before. As mentioned above, more tuning's still in order. I already dropped main jetting down 5 numbers, and there's more there because there's no light throttle cruise tip-in surging yet... that, and just off-idle (maintaining ~50KPH) there's wee bit of burbly kinda surging (rich), so I'll try slightly bigger idle air bleeds. It's already running night-and-day differently as to smooth and quiet slow idling and running, crisp responsiveness, and it doesn't suck back the gas anymore... so we're gettin' there.

    The ignition with that module is working great. When I checked for coil spark before starting it up, there was a nice fat Tesla-spec lightning bolt jumping over a 5/8" gap to ground, lol... With replacing TFI, I was starting from ground-zero with just a Duraspark II distributor, so the bucks-down approach is what I took and it works fine. With my mechanical advance curve, I did have to limit the vacuum advance some to where it liked it though. All part of the super-tuning, and continues...

    Thanks for stopping by here
    Last edited by Walking-Tall; 08-22-2016 at 02:55 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  11. #161

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    Today I repaired (drive, nose bushing, and grease here'n'there) and put the starter back in with new bolts and lock washers. Quick'n'quiet spinning now.

    Installed a 1/8" restriction to the return fuel line and it's now got a steady 5.5-6psi fuel pressure. Re-adjusted float level and idle mixture screws.
    Last edited by Walking-Tall; 08-22-2016 at 03:02 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  12. #162

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    Carburetor calibration as of 09-02-2016:
    - Idle Air Bleeds - Ø0.070" (changed today, up from Ø0.066". Cleaner, smooth running off-idle and cruise)
    - High Speed Air Bleeds - Ø0.027"
    - Idle Feed Restrictions - Ø0.038" (went back up here (from going down to Ø0.027", from the factory Ø0.036"), due to slightly stumbly off-idle checked out (plugs & O2 sensor voltage) as too lean)
    - Main Kill Bleeds - Ø0.028"
    - Accelerator pump shooter - #31 (needs a smaller shooter. Verified today unsuccessfully trying to hole-shot somebody off a green light, lol)
    - PVCR's (power valve channel restrictions) - Ø0.073" (*0.0042in²)
    - Main Jets - #68 (Ø0.069" - *0.0037in²) (These can still be reduced, and will be...)
    - * Total fuel flow area for WOT for each throttle bore = 0.0079in²
    Last edited by Walking-Tall; 09-03-2016 at 12:12 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  13. #163

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    She smoothly accomplished 16+:1 air:fuel ratios ((100mV (and less. As low as 25mV registered in a few instances) from the O2 sensors). It likes to idle at about 750mV, which is about 14.6-14.5:1, with 12-degrees BTDC initial timing and ~10-degrees vacuum advance connected to intake manifold vacuum. Total initial+mechanical advance is 36-degrees BTDC at ~3000rpm) during all modes (minus <8.5"Hg vacuum levels... the chosen 8.5"Hg power valve doesn't account for the lack of power this thing has, that's pretty easily loaded with it's 2.73:1 gearing, such that 8.5"Hg is pretty much normal acceleration to get 'er going, and that's not where the extra enrichment is necessary at all. So, I ordered a 4.5"Hg power valve, and that should be better suited... and ordered two more two-steps down for main jets to continue until it shows me a sign of surging. Between the off-idle mixture and timing curve to fire lean mixtures, it hasn't hinted at surging yet...) of off-idle and highway cruise today... with, what, a carburetor?




    We celebrated




    Here's where we're at, and it's working darn good:
    Carburetor calibration as of 09-10-2016:
    - Idle Air Bleeds - Ø0.074"
    - High Speed Air Bleeds - Ø0.027"
    - Idle Feed Restrictions - Ø0.029"
    - Main Kill Bleeds - Ø0.028"
    - Accelerator pump shooter - #31
    - PVCR's (power valve channel restrictions) - Ø0.051" (*0.0020in²) (4.5"Hg power valve ordered)
    - Main Jets - #68 (Ø0.069" - *0.0037in²) (#66's & #64's ordered)
    - * Total fuel flow area for WOT for each throttle bore = 0.0058in²
    (No, I have not done much of any WOT testing yet (have I let 'er rip here'n'there? F-ing right I have, and she roars and hauls ass, lol), but it's still safely rich...)
    Last edited by Walking-Tall; 07-19-2017 at 11:56 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  14. #164
    FEP Member 9D83's Avatar
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    'oer the border
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    And looked great doing it!

  15. #165

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    Quote Originally Posted by 9D83 View Post
    And looked great doing it!
    Thanks, bud
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  16. #166

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    By putting blanks into the PVCRs, blocking them, I verified that the #68 jets are fueling plenty for any amount of accelerating prior to roughly 3/4-throttle to WOT, and nowhere near enough fuel for WOT, lol. The 4.5"Hg power valve and #66 & #64 jets should be here Monday, and then I'll see what's what with Ø0.051" PVCRs reinstalled, and I'm going to go straight to trying the #64 jets to see if there's any light acceleration surging prior to power valve opening. It really likes the Ø0.029" idle feed restrictions in combination with Ø0.074" idle air bleeds, with crisp, smooth response to light acceleration within the idle/transition circuit. With one eye also on oxygen sensor voltages, 750mV (14+:1 AFR) at idle decreases to as low as 50mV (~17:1 AFR) with light-to-moderate acceleration.
    Last edited by Walking-Tall; 09-17-2016 at 07:38 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  17. #167

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    It didn't like the #64 jets, or the #66's, with immediate part-throttle protest, lol. So, #68's are optimal, and went back in. In conjunction with trying smaller jetting, I also installed some Ø0.043" PVCR's. It didn't like that at all either. Too lean WOT. Reinstalled the Ø0.051" PVCR's, and will see how it acts tomorrow. PVCR enrichment later, with the 4.5"Hg power valve, is definitely better with this lo-po mo-sheen.

    So, here's where we're at with a Holley List #4412-2 500cfm 2-barrel on an '86 3.8L V6:
    Carburetor calibration as of 09-19-2016:
    - Idle Air Bleeds - Ø0.074"
    - High Speed Air Bleeds - Ø0.027"
    - Idle Feed Restrictions - Ø0.029"
    - Main Kill Bleeds - Ø0.028"
    - Main Jets - #68
    - Accelerator pump shooter - #31
    - Accelerator pump cam - Pink
    - Power valve - 4.5"Hg
    - PVCR's (power valve channel restrictions) - Ø0.051"
    Last edited by Walking-Tall; 09-19-2016 at 10:33 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  18. #168

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    Remembered my camera can take video, and figured out how to do that today, enjoy, lol

    ~ Some AFR (mV from O2 sensor) video clips from today (don't mind the mess, we're testing gawldangit, LOL!)


    Idle, in Neutral and in Drive (14+:1):


    - Idles at 22"Hg (~650rpm) in Neutral and 19-20"Hg (~500rpm) in Drive


    Normal acceleration to 50KPH/30MPH (~15.5-16:1):


    - vacuum drops down to 8-10 with just normal acceleration, which is why the 8.5"Hg power valve was too soon


    Cruise @ 65KPH/40MPH (16.5+:1):




    Throttle blip on gravel, lol, and then a couple WOT's (~12.9-13.2:1)... on the lean side:


    - finally checked WOT after this with the pedal flat-on-the-floor and there was another ~1/4" pull required at the carburetor. So, in this video it wasn't actually going fully to WOT, which is also why it didn't kick down the 2nd time I trounced on it. I pinched a ~1/4" fishing line sinker onto the accelerator pedal end of the cable for that bit more pull. Now she opens wide.


    So yeah, I'm quite happy with her function, minus WOT. I'll feel better with PVCR's a bit bigger for ~12.5:1... to be continued...
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  19. #169

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    So today I went rippin' a bit again with multi-meter. I had changed out the Ø0.051" for Ø0.062" PVCR's. I know that's a pretty big jump, but I had drilled out the Ø0.043 restrictions I had to Ø0.055 and tried that, and that didn't make enough of a difference. Today we went WOT three different times, once from a slow rolling start through 1st and 2nd, and two times on the highway kicked back into 2nd from 3rd. The butt-dyno told me it's the smoothest but most violent and hardest it has pulled yet, and the multi-meter read ~925mV, which is right in the neighborhood of 12.5:1 AFR. I'll do a plug-chop some time and look at some plugs, but I'm calling it dialed in. A side note: I was tickled to calculate and find that gas mileage through all this monkeying around with the carburetor has been 18.5/22 MPG (US/Imperial). I can't wait to see how it does on a steady speed highway trip.

    Carburetor calibration as of 09-21-2016:
    - Idle Air Bleeds - Ø0.074"
    - High Speed Air Bleeds - Ø0.027"
    - Idle Feed Restrictions - Ø0.029"
    - Main Kill Bleeds - Ø0.028"
    - Main Jets - #68
    - Accelerator pump shooter - #31
    - Accelerator pump cam - Pink
    - Power valve - 4.5"Hg
    - PVCR's (power valve channel restrictions) - Ø0.062"
    Last edited by Walking-Tall; 09-21-2016 at 09:47 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  20. #170
    FEP Supporter
    qikgts's Avatar
    Join Date
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    Location
    Rockledge, FL
    Posts
    1,458

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    Enjoying the detailed and informative updates. Thanks for sharing them.

    Perhaps others more skilled in tuning than I already understand the effects of different changes to these circuits; I'm really glad you're sharing these practical examples and hope I can learn something from it.
    '85 GT

  21. #171

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    Quote Originally Posted by qikgts View Post
    Enjoying the detailed and informative updates. Thanks for sharing them.

    Perhaps others more skilled in tuning than I already understand the effects of different changes to these circuits; I'm really glad you're sharing these practical examples and hope I can learn something from it.
    Thank you, I'm glad you are. You're welcome, and thanks, I appreciate that.

    This is admittedly the first time I have dove this deep into dialing a vehicle in for best efficiency. It takes a fair bit of doing things, sometimes repeatedly and/or in the other direction, because the whole exercise is an investigation as to where the vehicle is at, and to figure out which direction to go, find out where the lean/rich limits are, and then zero in, one step at a time so you know what the affect of a change was, working to provide exactly what it wants or needs to function efficiently. Anything more is just an unnecessary waste of fuel. Getting the idle, low speed, and lower end mid-range right is the most time consuming, though there are a couple initial and pretty quick telltale tests that get you close and headed in the right direction, and IMHO these things should be tackled first. Also IMHO, idle and transition is the most important and rewarding to get right, because most modes of operation besides upper-moderate to hard acceleration and wide open throttle, are all in the express control of the idle and transition circuits, including even higher highway speeds' fuel efficiency... and with efficiency and giving an engine what it wants, comes more power. This technology is ~100 years old. It's too bad it's never fully been set in motion, besides in earlier days when mass produced vehicles made with carburetors gave more incentive for things to be designed and done right or at least better. EFI can only dream about the fuel efficiency like this. With a carburetor, there's no switching above and below "stoichometric" to provide an average so that a computer can continue fueling and switching above and below making an engine theoretically run an AVERAGE "stoichometric" mixture of 14.7:1. Any engine, in conjunction with the correct amount of ignition advance, can smoothly, efficiently and safely run on air:fuel mixtures notably much higher than 14.7:1, consistently, full time, without switching above and below a safe compromise, and then leaving heavier engine loading and WOT to more safe compromises of timing and fueling. IMHO, yes, there's been increased technology, but there really hasn't been progress, not in the realm of fueling and ignition there hasn't. Forcing engines to do things they otherwise wouldn't ever do or be able to do, isn't progress.

    I guess that went kinda ranty, lol... Rant over.

    On that note, that some of these procedures I'm getting a handle on are new to me too, if there is anything I can bring clarity to about these things I've posted about for anyone, don't hesitate, ask away if you've got questions! If we don't know, we can certainly try to find out or figure it out.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  22. #172

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    Cold, rainy day ramblings and thoughts:

    Considerations for fueling with a stock or very mild engine, where manifold vacuum at idle is usually about twice that of the vacuum seen at level road cruising loads, simply because the engine's not very powerful, and in combination with rear axle gearing that does not take advantage of that comparatively low horsepower.

    The above is the opposite of a "warmed up" or modified higher horsepower engine and vehicle, where, for instance, manifold vacuum might be something like 10"Hg at idle, and then loafing with ease down the road it sees upwards of or more than 20"Hg...

    Transition slot exposure of ~0.020" below the throttle plates provides readiness to go to work for when the throttle starts to move up their length, with their exposure above the plates providing bleed or anti-siphon air prior to throttle movement, so that they do not go to work before they should. Correct position and function leaves just the idle discharge port holes below the throttle plates in the throttle bores, controlled mostly by the idle mixture screws, to be what provides the air:fuel mixture for idle, in combination with the idle setting's slight throttle plate opening for air, and a PCV's airflow air.

    Cutting to the chase, lol:
    I may restrict PCV flow with this thing, because the couple times I've had the carburetor off, to enlarge the idle air bleeds, I've noticed that the transfer slots' exposure at idle is less than 0.020", at about 0.010". I blocked the idle air bypass holes in the throttle plates that Holley 4412 two-barrels come with from the factory, knowing that this stock little 3.8 definitely would not need the bypass air, but I think that the PCV valve is providing a bit more of a vacuum leak/bypass air than is necessary, judging by how little the idle speed screw opens the throttle plates for idle... and I also think this condition (good high manifold vacuum at idle AND PCV bypass air) is producing the very sensitive and minimal counterclockwise-from-lightly-seated setting that the idle mixture screws end up being at. In this situation of mine, I think that minimal transfer slot exposure acts very similarly to a too-small idle air bleed, which simply causes more suction to air:fuel that goes through/past the idle mixture screw orifices/needles, out the idle discharge holes, into the engine, and I think a bit more transfer slot exposure below the throttle plates might allow the idle mixture screws to be opened further more so where they should be, and to not be so touchy and at ~5/8 turn out. When I say touchy, I mean a slight rotation in or out, like the width of the small flat screw driver used to turn them, makes pretty big differences... and shouldn't. (The holes the needles seat in aren't oversize, and the screw needle tips are not out of the ordinary)

    Thoughts?...
    Last edited by Walking-Tall; 09-23-2016 at 02:22 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  23. #173

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    I noted mileage at each fuel stop after zeroing the trip-odometer, and noted it's fuel usage each time over an 1800+ kilometer (1100+ mile) trek, and... results:





    So, the carburetor and ignition tuning that had been done previously, which was by no means exact rocket science, not going so far as to finding the stupid lean points, changing the idle feed restriction and idle air bleed sizes, has paid off largely already. I'm pleased and impressed, lol
    Last edited by Walking-Tall; 07-20-2017 at 12:07 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  24. #174
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    qikgts's Avatar
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    Great economy! Where do you think your average speeds were for each leg?
    '85 GT

  25. #175

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    Quote Originally Posted by qikgts View Post
    Great economy! Where do you think your average speeds were for each leg?
    The first bits were slower speeds here and there, in and out of small towns and such along highways, with ~90Km/hour or about 55miles/hour being the most, running ~2000rpm.

    It actually got that near-34MPG mileage the on the second last leg, when speeds were faster, around 110Km/hour or ~68miles/hour (~2500rpm). This backs up my thoughts about low RPM not necessarily being the best thing for fuel efficiency, especially with a lower power vehicle, like this car's ~120 horsepower, it labors notably more at lower highway speeds, as seen by manifold vacuum levels (I've got a vacuum gauge on the dash) while driving, and loafs along much easier, with higher vacuum readings (less load = pedal not as far pressed down = less fuel use), at the higher speeds.
    Last edited by Walking-Tall; 10-07-2016 at 08:58 AM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

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