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  1. #1
    FEP Power Member 86darkside's Avatar
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    Default 331 efi vs 331 carb

    hey guys im building a 1986 mustang gt roller from the ground up i have been toying with building a 331 stroker but need some input
    its going to be 95 percent street car


    stock block =budget reasons
    331 stroker kit from lmr the scat version listed
    trick flows top end kit the street version
    what type of injectors...36? and whos?
    header size..?
    also what computer to use..? will probably need a chip or tune..?


    331 carb
    same as above but with victor jr intake
    what size carb..? 650 holley?

    t5 from 93 cobra

    anything im missing ....comments...advice...?

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  3. #3
    FEP Super Member erratic50's Avatar
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    Does that 5% track car wish to turn corners or make passes on the drag strip?
    --> If it wants to do both then the decision is EASY.

    Does that 95% street car expect to be driven when it's cold outside?
    --> if yes, how much cam and intake does this 95% street cat think it needs?

    If corners, cold, or cam&intake then my thought is EFI.

    not less than 70 or more than 75MM MAF
    Not less than 65MMor more than 70MM throttle body


    Typhoon EFI 1500-6500 intake or if you are made of more money, Edelbrock or better yet lower ported on a tubular GT40.


    I would call Anderson or COMP or both on cam. Or get detailed recommendations with dunno sheets where possible from guys here.

    Lifters- crank the oil pressure to the moon or get comp or Sherman short stroke hydraulics. Strongest pushrods possible. Match springs to cam and lifters.

    Injectors I'd go EV6 with adapters-- for better atomization.

    Tune I'd go binary editor and moats quarterhorse and A9L. Cut it off at 6500 due to stroke physics for reliability

    Headers I'd go equal shorties, 2.5" high flow cars, SLP loudmouth catback.

  4. #4

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    Simulating (500-6500rpm) that TFS kit's parts, and the 9.5:1 CR (not sure how they got there... block and head machining I presume (bolt-on CR would be less than 9:1)) 65mm TB EFI 306, arriving at their quoted 350HP/370TQ... using 1-3/4" long tube headers and full (cat-less) exhaust...


    Then changing it to 331, CR to 9.11:1 (11cc pistons & 61cc chambers), and to a 70mm TB and 24LB/HR injectors:
    380HP @ 6000rpm & 406FT-LBS @ 4000rpm, with 230HP & 331FT-LBS averages

    Then changing induction to a Vic Jr intake and a 750cfm carburetor:
    465HP @ 5500rpm & 450FT-LBS @ 5000rpm, with 260HP & 358FT-LBS averages



    That TFS camshaft really could use some more compression. Upping the CR to 10:1:

    TFS EFI 70mm TB:
    395HP @ 6000rpm & 417FT-LBS @ 4000rpm, with 237HP & 342FT-LBS averages

    Vic Jr & 750cfm carburetor:
    475HP @ 5500rpm & 460FT-LBS @ 5000rpm, with 266HP & 365FT-LBS averages



    Personally, I'd choose the unhindered airflow of the carburetor's higher peaks and averages, and less expense (it is a nice kit with lots of parts. The heads themselves are half the cost), and live with or maybe add some more rear gear for the (higher) torque peak that arrives 1000rpm later. A high rise dual plane intake manifold would reduce the peak numbers some, and should lower the rpm when peak torque happens.

    Either induction system eclipses 300FT-LBS before 2000rpm & 400FT-LBS by 4000rpm. Comes down to dollars and ability to modify or dial in the system, IMHO, and with modern fast burn combustion chambers, the ignition timing curve that makes the most and safe power has it's total timing limited/optimized. Not easily or inexpensively done with EFI... software, chip, tune, yadda yadda, more $...

    Whichever way you go, good luck with it. Should be fun
    Last edited by Walking-Tall; 10-14-2017 at 09:41 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/

  5. #5
    FEP Power Member 306gt's Avatar
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    Personally I'd go with the carb, Less aggravation for tuning, if you know how to play with the carb. Less underhood clutter, cleaner install, makes things simple and you are not held hostage to a tuner. Both set-ups will make similar power. 400HP To the wheels is easily done if you pick the right parts. Mine has a 650 d.p. Victor Jr. AFR185's. T-5 and 4.33 gears makes 390 rwhp and runs mid 11's -118-120 mph at 3350 lbs.
    85 G.T. All motor
    337 c.i.d 11.44-120 mph

    1984 1/2 G.T. 350 (13.01-106 mph)

    1984 G.T. (Daughters car)

    1986 G.T. (Son's car) (12.99-105 mph)

  6. #6
    FEP Super Member erratic50's Avatar
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    EFI setups are often more drivable on the street and in corner carver situations.

    That being said, there's just something about the moan of a well tuned carb on top of a properly tuned motor. I miss that enough that I'm building my 85 Saleen clone with a carb rather than factory 86-93 style EFI.

    Some of the aftermarket self tuning setups are really attractive in spite of their cost over and above either carb or factory style EFI.

  7. #7
    Moderator wraithracing's Avatar
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    I tend to prefer EFI over the carb as EFI when setup properly is hard to beat on the street and for DD type duties.

    The other reason is a bit more simple. . . . . 86 GT should stay EFI!
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  8. #8
    FEP Super Member erratic50's Avatar
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    Agree ! EFI cars should stay EFI. It takes a lot more effort to bring the 79-85 cars up to the 86+ EFI setups.

  9. #9
    Moderator wraithracing's Avatar
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    The 86 car is a one year only wiring harness in so many areas that is seems crazy to me to either yank it out or just leave it to go carb.

    I completely agree on upgrading the engine and EFI setup to really maximize the power, but I would still stay EFI. At least that's my .02 worth.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

    "I've spent most of my money on Mustangs, racing, and women... the rest I just wasted."

    Mustangs Past: Too many to remember!
    Current Mustangs:
    1969 Mach 1
    1979 Pace Car now 5.0/5 speed
    1982 GT Stalled RestoModification
    1984 SVO Still Waiting Restoration
    1986 GT Under going Wide Body Conversion Currently

    Current Capris:
    1981 Capri Roller
    1981 Capri Black Magic Roller Basket Case
    1982 Capri RS 5.0/4spd T-top Full Restoration Stalled in TX
    1984 Capri RS T-top Roller
    1983-84 Gloy Racing Trans Am/IMSA Body Parts

  10. #10
    FEP Super Member xctasy's Avatar
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    IMHO, each Fox should remain in the condition in which it was made....unless you know more than the FoMoCo...

    If its EFI, let it stay EFI.

    If 84-85 5.0 CFi, then you can go Port EFI with more ease that you'd ever believe possible.

    If 79-85 carb, it should stay carbed.

    If 79-86, you can go aftermarket non port TBi, then you've got any number of other options.

    A rewire of a Fox should probably entail keeping the fuel pump systems if it was born with the 83-86 2.3 Turbo or CFi 5.0 or 3.8 CFi or 5.0 EFI.

    That system was invasive and a real huge addition to the stock early modle Fox sytem, and its probably 80% of the carb wring differences right there.

    Butcha know...I really like Walkin'Talls CFI to Holley Carb conversion of his 3.8 V6.

    The most important single thing is that EFI engines make off idle to 3500 rpm torque like you wouldn't believe, and Foxes are light, and then the issues of preservation of your own life, the life of others, and the life of the Foxes power train from gearbox to axle to chassis is s "m0r@|" issue.

    Ending up in someone elses ash tray is more likely with the sort of torque an EFI 331 can put out.

    For me, I love the 4-bbl carb engines sound, and loss of off idle torque and in the 331 stroker, its bound to be a heck of a lot safer without the extra foot pounds between 650 to 3500 rpm. It's like loosing 19 cubic inches.

    When you add extra tractive effort of good 255 section or more tire hides, the real risk is increased aquaplaning in the wet, and how to preserve life and limb.

  11. #11

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    I think what comes under question more and more with some problems people have and/or inquire with here at the forum, and where reliability can wander here and there today in 2017, is the integrity of the 30+ year old wiring harnesses that are to without fail connect sensitive CFI/EFI system components in order for it all to work correctly for good long reasonable amounts of time. I'm sure a number of us by now have all run across just how fragile or deteriorated the wiring can become in these cars. If somebody wished to convert to or stay with fuel injection, fine and dandy, but I would suggest a very wise first move would be establishing, one way or another, by checking everything, or replacement, a known rock solid, robust wiring harness.
    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. #12
    FEP Power Member 86darkside's Avatar
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    i understand your gripe with leaving it efi but youre missing where i said its a roller and someone ripped most of the cables leading to the ignition side to the sterring and no its not going to be a corner carver so theres that i want it to drive only in summertime and maybe sometimes go down the strip so that where me choosing a carb comes into play cuase one i dont have the tunning money two there the harness issue im having and three i want it to go the less headeach way ..thank you all for your opinions..

  13. #13
    FEP Power Member 86darkside's Avatar
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    also where could i find a place for a distributor for such motor..?..i dont want to use a msd.

  14. #14

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    Rock Auto lists some complete and nicely priced new distributors, like the POWER SELECT/WPS DST2831B. Make sure to get one with a steel gear if using a roller cam, and any pre-'85 302 Duraspark II distributor (vendor, bone yard, ebay, etc.) with a cast iron gear works with flat tappet cams.

    Link to '85 Mustang 302 distributors at Rock Auto: http://www.rockauto.com/en/catalog/f...stributor,7108
    Last edited by Walking-Tall; 10-18-2017 at 04:55 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/

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