'86 EFI 302 to Carbed 302 transition....

Discussion in 'Fox 5.0 Mustang Tech' started by rustyfanz, Jul 14, 2008.

  1. Alright, I am working on a project 89 Mustang LX, 5.0L convertible. The motor, a 302 ho, and tranny were both blown and i had a built of 302 and a c6 that I put into the mustang. HOWEVER, my question is this....

    We got the built up engine, a 3o2, out of a mercury grand marquis. It didnt have any knocks and had good oil pressure, it was a great engine. However, we changed it over from EFI to Carbed (we put a Edelbrock VictorJR intake and Edelbrock 4bbl 650cfm carb on it) with headers. However, we didnt change the distributor because we didnt think we needed to...

    The mustang runs alright, and is deffinately drivable, but it doesnt have as much get-up and go as it should with a torquey, rebuilt c6 tranny and a good, built up 302. could the distributor, coming off a 302 efi engine, be whats holding the engine back? Is there a difference between a distributor from a "pre-86" carbed distributor and a "86-and later" efi distributor?

    Any Help in this area works. Will I need to get a different distributor or go points (isnt a problem) and purchase a distributor like a mallory or something???
  2. Grand Marquis, Crown Vics, and Town Cars got the crappier "non-HO" version of the 302 from '86 to '91 (the Town Car got the 4.6 in '91, everyone else in '92) which feature a lame cam with a different firing order, flat-top pistons, a more restrictive (and backwards) upper intake manifold, smaller TB and EGR spacer, 14# injectors, different ECM, and some of the crappiest cylinder heads ever found on a 302. They were rated stock at around 150 horses at the flywheel; HO motors were 200 HP in '86 (flat-top pistons, restrictive intake, and crappy heads like the non-HO's), and 225 HP on '87+ models.

    If you're running a stock longblock assembly from a non-HO motor, it's no surprise that it doesn't have any get-up-and-go to it. You're operating with 50 to 75 fewer horses than an HO motor in stock form. :shrug:

    You can slap on a set of E7 heads from an '87+ Mustang or F-150 302, but unless you change over to notched pistons, your choice in cams is limited by piston-to-valve clearances. I've heard of guys running an E303 cam in a lo-po block with E7 heads, but I wouldn't chance it, myself, and definitely wouldn't go with any cam more aggressive than that.

    The distributor you have on there is fine, just so long as you have the plug wires arranged to an HO firing order and not the Grand Marquis (non-HO) firing order. It's a roller motor, just like any other '86+ 302, as far as that goes, so upgrading the dizzy would pretty much be a waste of money on a mild setup as far as performance. But if you're ditching the ECM, you'll need a stand-alone distirbutor, so in that case you would have to go with an old-school Duraspark dizzy and ignition setup, or get one of those stand-alone HEI setups from Proform with the groovy one-wire hookup.

    The biggest differences between the non-roller ('84 and earlier) and roller ('86 and later, and the '85 HO's with 5-speed) motors are the cam gear material. Old ones used brass or cast iron, the newer ones use a steel gear; if you go putting one into the other, the one with the softer metal is going to get chewed up all to hell. Also, on the '84 and older non-roller motors (not including CFI motors), they used a Duraspark ignition with an ignition box that was separate from the distributor and not controlled by an ECM, whereas the newer EFI motors (and CFI) used EEC-III and EEC-IV systems with the TFI module mounted right on the distributor. Sooooooo, if you do elect to get a different distributor, bear in mind you'll need a dizzy with the STEEL cam gear for a roller motor - perhaps swap the gear off your stock unit to the new one, if all else fails.
  3. All distributors built for use with a carb had a built in mechanism for spark advance. EFI distributors don't have any built in mechanism to advance the spark. The spark advance is provided by the computer. Without a fully working EFI, the computer cannot provide any spark advance. This means decreased performance and economy. An 85 5.0 Mustang has the distributor you need with a gear compatible with the roller cam.

    Some more comments about EFI to carb conversions...

    A word of warning on EFI to carb swaps: don’t expect to pass emissions in any state that does comprehensive smog inspections, because it won’t happen. Be aware that you are violating several Federal laws concerning the removal of pollution control equipment. If you operate the vehicle on public highways and get caught by state or federal law enforcement (doubtful, but possible) you could be subject to fines and imprisonment. You won't get any more power from a carb than you will from EFI.

    The following information is intended for informational purposes only. Operation of a motor vehicle modified in such as manner as described below should be limited to off road use only.

    Doing the swap: You must know how to read electrical diagrams and wire circuits properly to do the swap. Don’t take shortcuts or cut corners in the fabrication of the electrical or mechanical assemblies. If you do NASCAR quality work, the car will look good, run good and be as reliable as a carb’d car can be. Take pride in a job done with excellence.

    If you are one of those few people who do excellent work, please disregard my negative comments. They are not intended for you.

    Quality, quality, quality…
    Some of the motivation of my negative comments about carb to EFI has to do with the quality of electrical workmanship. A lot of the wiring “repairs” that I have seen on the road and in the junkyard looks like road kill. The other part of my negative view stems from people who can’t grasp the operation and tuning of EFI. Carbs have their own set of requirements and some learning is required to get the best performance. Every car is different and each installation needs to be tuned to get the best performance. Putting an “out of the box carb” or one from someone else’s car isn’t the way to success. There is no auto compensation for small variations in carbs like there is for EFI. Just throwing a carb on a car because you won’t bother to learn how EFI works is a poor excuse.

    Now that the rant is over, here’s some practical advice…

    Do not use an EFI in tank fuel pump with a carb. You will never get the pressure/flow regulated properly. Either go full EFI or use a tank/fuel pump/fuel lines out of an 84 or earlier Stang. Fabricating your own setup is possible but there are some snags to overcome.

    Do not attempt to leave the EFI in place in an attempt to control either the electric fuel pump or ignition. Doing so qualifies you for the “Road Kill Mechanics Award”.

    If you try to use your current tank, you will need to pull the fuel pump out and fabricate a pickup tube & strainer sock to replace the fuel pump. Or you can have a sump fabricated and welded onto you existing tank. Many welding shops will not weld fuel tanks because of the dangers involved if the tank isn't purged properly.

    You will need an external electric fuel pump unless you change the timing cover for one with the mechanical fuel pump mount on it. Rip all the EFI wiring out, and the computer controlled fuel pump won't work. You will need to add a relay & switch and wire in the existing inertia switch for an external low pressure electric fuel pump. Do not try to wire the fuel pump without the relay. The 15-20 amps the pump pulls will overload the circuit. This will take power away from other items on the same circuit or cause the fuse or fuse link to blow.


    You will need to run some new fuel feed lines or braided hose. The 3/8" aluminum tubing works well, but you will need a flaring tool and bending springs to fabricate the lines. Braided hose is easy to run and route, but is much more expensive. It is about $3.50-$4.00 a foot plus the end fittings, which are $3-$4 each. Fabricating hose assembles can be difficult, but anyplace that makes hydraulic hoses can do it for you for an extra charge. See Amazon Hose and Rubber - Industrial Hoses and Hydraulic Hose Assemblies since 1919 for more information.

    For stainless steel braided hose and fittings for automotive use:

    See summitracing.com

    stainless steel hose - JEGS High Performance

    See Eaton Aeroquip > Performance Products for more information on High performance automotive hose products

    AN fittings require a 37 degree flaring tool. A standard automotive or household plumbing tool is 45 degrees and cannot be used with AN flare fittings. If you do, the flare is subjected to too much stress when the fitting is tightened, and is likely to fail or leak.

    See MSC Industrial Supply Co. Home Page , McMaster-Carr or for the flaring tool you will need . Prices start at $75 and go up

    Tailor Made Servers


    While you are at the electrical part, you'll need a Durspark or similar ignition system. The 85 Mustang GT 5 speed has a suitable Duraspark distributor with a steel gear compatible with the roller camshaft. The EFI ignition depends on the EFI sensors to advance the spark. Rip out the TPS and MAP/Baro sensors and the computer will have no idea of the proper ignition timing for best performance. Running a fixed timing setting is only for test purposes or for a race track only car. Don't try it on the street: the results will not be nearly as good as a properly setup Durspark or equal. Crane makes a really nice distributor for non-EFI applications. . See CraneCams for more information.

    Tools needed:
    Crimp tool for connector pins $9-$30 AutoZone, NAPA, Advance Auto Parts or other store
    100-150 watt soldering gun (recommend WELLER 8200PK soldering gun kit 100/140W) $30 at Lowes or $40 at Home Depot
    3/32”-1/8” rosin core electrical solder, 1/4 lb roll $6 at Ace Hardware, Home Depot or Lowes
    Assorted sizes of heat shrink tubing. Buy long pieces and cut length to fit. It is cheaper that way. Parts-Express.com - Heat Shrink Index: 2:1 Ratio, 3:1 Ratio, Heat Shrink Kits
    Hot air gun to shrink the tubing ($30-$40) Home Depot
    Jeweler’s screwdriver kit $5 at Ace Hardware
    Assorted automotive wire, 18-16 gauge 10’-20’ foot spools in different colors. $5 a roll at Advance Auto Parts.
    Ford connector pins AutoZone, NAPA or other store $5-$10 for a kit of 10-12 assorted pins

    You will have $110-$150 in materials and tools if you don't already have them.

    The water temp and oil pressure signals feed from the sender to the main harness through the 10 pin EFI engine harness. To utilize these senders, you need to identify the wires and find a way to reconnect them to the main harness after the EFI engine harness is removed. You need a weatherproof quick connector to join the sender wiring to the main harness.

    You will need to construct a wiring harness from the ‘85 carb distributor to the Duraspark box if you go Duraspark, or other distributor to coil wiring.
    The voltmeter picks up its signal from the switched voltage present on the instrument panel, so you don’t need to worry about that.

    The fuel tank gauge is also independent of the computer wiring.

    AutoZone wiring diagrams

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs

    How to solder like a pro - Ford Fuel Injection How To Solder Like a Pro a must read for any automotive wiring job.

    Soldering pigtails onto existing pins is road kill quality work as far as I am concerned. Take some time to study the way the Ford connectors are assembled and you will find that a small jeweler’s screwdriver will release the pins from the connector shell. New pins and a crimping tool are available from the Standard Motor Parts or Bendix Electrical parts line that the NAPA & Bumper to Bumper Auto Parts stores carry. Ask any auto parts store about Standard Motor Products or Bendix Electrical wiring parts. Those that carry them will be able to get the parts you need. AutoZone has a cheap kit with 10 pins for about $5. Just enough pins to leave you short when assembling a connector.

    One of the interesting things about the Ford OEM wiring diagrams is that the connector shape on the drawing matches the connector shape in the car. That makes it easier to identify connectors and circuits. OEM Ford diagrams are available at for an 85 Mustang at Helm Incorporated: Search Results or can be found in the Chilton series of auto repair manuals for Mustangs.

    The following is an excellent idea from a fellow Stangnetter who tackled the wiring plan the right way. He obtained the wiring diagrams from an 85 carb'd V8 Mustang and laid them out side by side with the diagrams from his car. He then traced out each circuit and the wire colors and connectors associated with them. After tracing the circuit and connectors for a circuit, he laid out the changes he needed to make. One circuit at a time made a difficult big job into many smaller easy to manage jobs.
  4. Thanks guys.

    First - i dont plan on keeping the 302 from the grand marquis in there. I planned on swapping the intake w/ carb and the headers over to the 86 HO that came out of the mustang as soon as I replace the valves (they were shot and a couple were bent from lack of care to the motor by the previous owner.) I was just making sure that i could still use the distributor (which, if I read correctly, i CANT) because both the distributors from the grand marquis and the mustang are relatively the same (the grand marquis dizzy hooked right up to the plug off the mustang dizzy).

    Second - we didnt leave the old fuel pump on there, it wouldnt have worked anyways because it puts out WAY more pressure than you need for a carb. I took the fuel pump out of the tank and ran a hose from the tank through the old fuel pump assembly (with the fuel pump no longer on) and ran it to a 7-10 psi aftermarket, out of tank, fuel pump. Then I ran my own line and succured it to the car (correctly and "nascar-like") straight to the carb. It works like a dream!

    ANYWAY, now that I see that the dizzy wont work, I will get one, (if i read correctly, that is) a dizzy off an 85 mustang with a steel gear (or a standalone aftermarket dizzy) and put it in and wire it up, as per the wiring diagrams. <----However, if I am not correct someone please correct it so that I can get the correct setup...

    On another note, as per the rant about it being illegal, i really dont care much about that. I have NEVER seen anyone pulled over and a police officer (that actually knew anything about motors) pop the hood and make sure that someone had their smog control hooked up. I live in Nebraksa, and currently we dont have a "smog laws" and I doubt we will in the very near future. I dont plan on ever moving to California or any state that has emissions laws.... That was my little rant.:rolleyes:

    Thanks guys for your help and if anyone has any more tips or suggestions, feel free to post:nice:
  5. Geez you guys throw down some brick wall posts...lol.

    1, the EFI distributor won't work. Get one from an '85.

    2, although strong, that C6 is gonna soak up more power than an AOD or T5.

    3, there's a LOT of performance to be had in the mechanical advance in the stock '85 distributor. Do a web search about locking out the mechanical advance and it'll tell you all kinds of cheap tricks for modifying them for much better performance.

    Lastly, and this may not be your case but just for the record...being a carb supporter i'll be the first to point out that simply swapping to a carb setup doesn't mean you're gonna automatically be faster...nothing is that simple.