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Thread: 3.8/4.2L Split Port Swap into a Fox

  1. #1
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    Default 3.8/4.2L Split Port Swap into a Fox

    Bottom line, the CFI 3.8 is a stinky turd.

    What do you do to remedy this? The easiest way is to swap in a 5.0. However, if you are mentally deranged like myself, a Windsor V6 upgrade looks like a feasible option.

    There are a multitude of later model 3.8s to throw in:

    1988 Fox --- (SD - MPI)
    '89-'90 MN12 (SD - ?)
    '91-97' MN12 (MAF - SEFI)
    '94-'98 SN95 (MAF - SEFI)
    '99-'04 SN95 (MAF - SEFI)

    There are many more differences between the engines and peripherals than the SD/MAF and MPI/SEFI designation, but it makes for a nice arbitrary compartmentalization.

    Now that one knows where to grab a better 3.8L, the questions becomes, which 3.8L do you grab? Since the main reason for the swap is a power increase, let us sort them by power output:

    1984-1987 Fox - 120 hp@3600 rpm -- 205 ft-lb@1600 rpm
    ------1988 Fox - 140 hp@3600 rpm --205 ft-lb@1600 rpm
    1989-1995 MN12 140 hp@3800 rpm --215 ft-lb@2400 rpm
    1996-1997 MN12 145 hp@4000 rpm --215 ft-lb@2750 rpm
    1994-1995 SN95- 145 hp@4000 rpm --215 ft-lb@2750 rpm
    1996-1998 SN95 -150 hp@4000 rpm --215 ft-lb@2750 rpm
    1999-2000 SN95 - 190 hp@5250 rpm -220 ft-lb@2750 rpm
    2001-2004 SN95 - 193 hp@5500 rpm -225 ft-lb@2800 rpm
    1996-2003 WStar 200 hp@4900 rpm - 240 ft-lb@3600 rpm
    1997-2005 Truck -200 hp@4700 rpm - 250 ft-lb@2700 rpm (4.2L)

    The engine slowly gained power through the years, but the major change was the introduction of the split port intake. The split port's large power increase (>25&#37 makes it the prime swap candidate.

    The swap can be done in a multitude of ways, but the most direct is to take an entire engine, EEC and harness from a '99-04 Mustang. There are several things to be aware of though.

    Clearance -

    The Mustang upper should clear a stock hood.
    The 4.2L upper almost certainly won't.
    The Windstar upper won't either.

    EEC Issues -

    Even after swapping in a complete EEC-V computer and harness, there are still problems. PATS, EVAP and the returnless fuel system. All three can both be turned off with an SCT flash - problem solved.

    Chassis Wiring -

    I've looked through my EVTM's and can't find which wires interface with the EEC harness. However, whatever they are, a little "custom" splicing and dicing will do the trick.

    Fuel Deliver -

    99+ Mustangs use a returnless fuel system. The problem is that Walbro type pumps will surge and die if run with PWM. Since the 99+ Mustang pumps (vane) won't drop in, you must modify the fuel rails to keep a return system. F150 or Windstar rails are normally the ones people modify to fit.

    Transmission -

    You can go manual or automatic. The easiest option is to just pull the 4R70W or T5 that came with the engine.


    Throttle Cable -


    Unsure if Mustang cable is long enough or will interface with the pedal correctly.

    A/C -

    Liquid line should work. Custom hoses needed for discharge and suction

    P/S -

    Pressure hose might work.

    Coolant Hoses -

    SN95 radiator has larger inlet/outlets than Fox.
    Water pump inlet and thermostat outlet are same for SN95/Fox.
    Upper radiator hose is the same length for SN95/Fox, might fit...
    Lower hose is 4" longer. Frankenhose may be required.
    Heater core inlet hose may/may not fit

    Tripminder -

    Microcontroller required to convert injector pulses, duty cycle to pulse-train equivalent to DOL. Use GUFB


    I'm sure I have missed several important items, but this is a draft to be built upon.

    I have focused on the 3.8, but you can swap in a 4.2 (or put 4.2 internals in a 3.8) too. The 3.8/4.2 heads are the same, the main external difference is in the size of the upper intake. The truck intakes are much taller, as seen below (L-R, 01+ Mustang intake, 4.2L intake, 99-00 Mustang intake)



    A few people have swapped in Windstar intakes, but those require 4" cowl hoods on SN95s. The following is a '96-'98 intake.




    The Windstar intake is actually the best power-wise. It makes 7 more horsepower and 25 more ft-lb of torque than a Mustang, and the Windstar has a more restrictive exhaust. This is due to the increased height of the intake. Also, as you can tell, the intake is plastic.
    Last edited by JeremyB; 05-09-2007 at 07:27 PM.

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    Excellent info. I've always wondered if a mass-air V6 computer would work with split port. Obviously you'd need one from a DIS car (such as Super Coupe or 94-95 Mustang) as a distributor would never work with an SPI intake. The IRCM system would obviously have to be removed as well...

    Some day I'm gonna do this swap to a four-eye as well, but I'd like to do one with a twin turbo setup. A twice-turbo'd 4.2 SPI engine could very likely make lots of power, it would be lighter than a 5.0 based engine, and with the engine's shorter length there'd be more room under the hood for the turbos as well.

    A question: What intake is used in the Econoline van? Is it the same height as the truck intake?


    'Nother question: Looking at Mitchell OnDemand it shows both a distributor and a DIS setup available for non-supercharged 94-95 T-Birds and Cougars. I had always thought only the supercharged MN12's had DIS. Was DIS available in NA cars, or is Mitchell OnDemand, as usual, full of shit?
    2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

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  3. #3
    Sduneman3 Guest

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    This is some good info... keep it coming!!!

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    Quote Originally Posted by Thunder Chicken View Post
    Excellent info. I've always wondered if a mass-air V6 computer would work with split port. Obviously you'd need one from a DIS car (such as Super Coupe or 94-95 Mustang) as a distributor would never work with an SPI intake. The IRCM system would obviously have to be removed as well...
    You can run a distributor with a Mustang SP, you just have to delete the EGR. [1] [2]


    Also, 99-00 cars did not have IRCMs. They were introduced in '01.
    A question: What intake is used in the Econoline van? Is it the same height as the truck intake?
    I don't know. I couldn't find any mention of the Econoline intake, only that the fuel rail was also useful in modifying for a return system (like the F-150).


    'Nother question: Looking at Mitchell OnDemand it shows both a distributor and a DIS setup available for non-supercharged 94-95 T-Birds and Cougars. I had always thought only the supercharged MN12's had DIS. Was DIS available in NA cars, or is Mitchell OnDemand, as usual, full of shit?
    IIRC, 94-95 cars with California emissions have DIS. 49 state cars have distributors.
    Last edited by JeremyB; 06-03-2007 at 01:03 AM.

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    The Econoline and Windstar Upper are both aluminum. I kept all the DIS stuff as well just for the heck of it. What stopped my 4.2 swap was my doner, spun bearings everywhere in the engine you see below. It sits in the corner of my garage now in the "WTF" pile o' crap.

    200 bux wasted. Im still not really sure on all the interfacing of the chassis to eec wiring to date and that would call for a stare and compare at evtms.

    I wasnt too impressed with the exhaust ports but if that was a part of making the extra power, then so be it, seemed rather small of an output , perhaps thats a part of the back presure game played into the engineering.

    And what about that GOD AWFUL huge oil pan? perhaps thats one issue that could be resolved in order to lower it. I took measurements and IMHO, it all would fit perfectly except for the pan and rack interferance. I sat both the 3.8 and the 4.2 side by side and to tell you the truth, it looked just fine sitting on the floor. In the bay, i dono but it will be close.
    Attached Images Attached Images
    Last edited by jcassity; 06-03-2007 at 11:48 PM.

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    The Windstar intake is plastic.
    Three 88's

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    Quote Originally Posted by CougarSE View Post
    The Windstar intake is plastic.
    This engine was out of a windstar 01. Intake is aluminum, maybe its one of fords many flukes on what got plastic and what got metal,,i dono.

    since mine is all torn apart,, do you need pics of any parts and whatnot?

    revised@brier.net ,,
    or ill postem here.

    scott
    Last edited by jcassity; 06-03-2007 at 11:54 PM.

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    and actually,,, to save all the time and hassel, get the 88 doner engine and swap in the 4.2 short block internals.

    your existing CFI harness is pretty much the same as the 88 with the exception of a few minor things to say the least. No oil pan issues either as well as intake. ,, unless you really like that fugly looking upper on the 4.2

    the problem with us who have the CFI setups are that we have external balance setups, thats why the 88+ is ideal for this upgrade. The 4.2 stuff is made for internal balance systems. I really dont know if you could just slap in the 4.2 stuff in the 87- blocks without major problems in the vibration area. Not to mention the harmonic does not bolt on to the 4.2 crank iirc.

    The 88 fuel injectors fire exactly like and at the same time as the CFI off pins 58 and 59 at the eec so thats another bonus in the No wiring department.

    I guess anyone could go with the 4.2 dis if they wanted to but that would take just a little more doing in the wiring dept.

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    '88 3.8s had the balance shaft, '87 3.8s didn't...how would this balance shaft affect swapping the 4.2 stuff in?
    '84 Mustang, work in (sloooooooow) progress...
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  10. #10
    DakotaEpic Guest

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    Wow, those are all some ugly intakes. Crazy stuff though. Good luck Jeremy. Oh and what's the deal with the V6's in the latest Mustangs?

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