Converting my 77 CJ to MPFI

Discussion in 'OT Driven' started by Meph, Jun 4, 2008.

  1. Meph

    Meph itchy trigga finga niggas

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    I'm in the process of converting my 77 CJ from the stock 1bbl carb to MPFI. I got the intake manifold off today, and as I expected, the new intake does not mate with the old exhaust manifold, so I'm going to order a set of headers and start working on the rest of it next week. I'll post some pictures of the project as I go along.

    Here's my Jeep:

    [​IMG]

    It's a 77 CJ7 with a 258 inline six. Everything is basically original and it has 90,000 original miles.

    This is the engine:

    [​IMG]

    And here is the new intake manifold:

    [​IMG]

    Basically what I am doing is taking a stock Mopar MPFI manifold with stock injectors, I will also be using the stock throttle body from that setup as well. I've got my wire harness built already, I'll post pictures of that as well. I am using a GM 1227730 batch-fire speed density ECM with TPS, IAC, MAP sensor, O2 Sensor and ECT sensor. I will be building a custom HEI distributor, locking out the mechanical and vacuum advance and installing a GM EFI module, so the ECM will control spark advance and fuel delivery. I have a new gas tank with a 75 psi in-tank fuel pump as well. Since I'm running headers, I will be using a heated O2 sensor, which will be installed in the collector on one side of the headers.

    Can't wait to get this bitch out on the trails. I took her out last year with just the 1bbl carb and she did alright, but this MPFI system will probably bump me up from 90hp to 150hp.

    Over the winter, I plan to rip the body off and install a new one that I bought from an 84 YJ. Within the next two years I'm going to take the 258 out and install a twin turbo tuned port 383 SBC stroker behind a 700R4. :)
     
  2. aim2kill

    aim2kill New Member

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    nice! keep us updated!
     
  3. Meph

    Meph itchy trigga finga niggas

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    Sweet, I'm glad this thread will generate some interest. It's going to be a fun project for sure!

    Just bought these headers:

    [​IMG]

    So, I guess I'll be running dual exhaust :big grin:
     
  4. IslanderOffRoad

    IslanderOffRoad Do you even lift kit? OT Supporter

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    please tell me you have, or will be, updating to the 4.0L head.

    My friend did this in his 81 CJ and its a night and day difference with the head and EFI. The 4.0L HO head flows so much better than the 258 head.

    Oh I want your crankshaft.
     
  5. aim2kill

    aim2kill New Member

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    a friend of mine did this with a little older CJ7, and according to the dyno, it was pushing almost 40 more ponies. i was quite amazed at the difference.
     
  6. Meph

    Meph itchy trigga finga niggas

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    I'm thinking about it. I have seen this done before as well, but I'm not sure if the 258 intake manifold will fit on the 4.0L head. It would be a good idea, and I might as well throw in a new cam while I'm at it, but I'll have to look around and see if i can find a 4.0L MPFI intake first. Probably not hard to find.
     
  7. aim2kill

    aim2kill New Member

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    i wounld think it would be hard to find. lots of crashed jeeps out there (the down side to trails...or yuppies driving jeeps)

    i know my buddy got his off of a rear-ended grand cherokee, not sure the year, but from Liberty pull apart in Lousiville, Ky.
     
  8. Meph

    Meph itchy trigga finga niggas

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    Can they be interchanged? I think they might use the same intake. I should probably just buy the head and cam, put them on and if the intake doesn't fit, then I'll look for a new one.
     
  9. aim2kill

    aim2kill New Member

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    dont quote me but i think they can. i think my buddy had to buy a gasket kit kinda thingy but it worked out well. his CJ runs like a champ.
     
  10. Meph

    Meph itchy trigga finga niggas

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    Yeah, I didn't even think about the fact that the intake I got was from a newer 4.0L. But, I'm going to hold off on the head right now, maybe change it out later.
     
  11. deusexaethera

    deusexaethera OT Supporter

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    I guess it's just me, but I'm amazed that anyone ever made non-crossflow cylinder heads. It's just so stupid to put the hot exhaust right next to the cold intake. But then, efficiency is a recent concern, it seems.

    Anyway, what's the port on the top of the exhaust manifold for? Is that just to support the intake manifold, or is it for exhaust gas recirculation, or what?
     
  12. P07r0457

    P07r0457 New Member

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    reverse-flow heads were less-expensive to manufacture (as well as simpler) and that was very important in the early days of automotible manufacturing. Furthermore, reverse-flow heads were benefitial in carburated applications -- especially with cold-starts.



    you wanna talk silly automotive design, why do many top manus (such as toyota) put the exhaust manifold in the FRONT and the intake in the REAR? They must pipe the exhaust under the engine (and under the intake). Other manus (such as volvo) put the exhaust at the rear, and intake at the front. This seems much more efficient, and less expensive.
     
  13. P07r0457

    P07r0457 New Member

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    not sure with his exact jeep... but some carb'd reverse-flow designs would actually link a chamber around the exhaust manifold to the intake manifold. This would help heat up the intake and aid with cold-weather starts, and low idles.
     
  14. Meph

    Meph itchy trigga finga niggas

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    Yeah, on most inline sixes the intake and exhaust manifolds link together to provide exhaust heat to the intake manifold. This is why most intake manifolds were made of cast iron back then. V6 and V8 manifolds usually have water jackets to heat them up.

    You have to understand that the concept is a lot different for carburetted and throttle body fuel injection manifolds. Not only is the heated intake necessary for better cold starts, it also helps the air/fuel mixture atomize properly inside the manifold.

    With multi-port injection, the air/fuel mixture is sprayed directly on the hot intake valve and instantly atomizes on contact. That is why it is more advantageous to have cold air in a MPFI intake manifold. They are also usually made of aluminum for better heat dissipation. This way you can allow cool air in the intake for increased density and better air flow and still get good atomization. You also get better control of air/fuel, which is why MPFI is so efficient.

    Our systems use an ECM controlled distributor, where the advance is controlled by the ECM based on vacuum, RPMs, intake air temperature, engine temperature, etc. If you use it in conjunction with a MSD 6A or 6AL ignition module, it elongates the spark duration for each cylinder, and there ends up being very little to no unburned fuel. Modern cars already have this with separate coil packs for each cylinder, or one coil pack for every two cylinders.
     
  15. Meph

    Meph itchy trigga finga niggas

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    Also, our systems are batch-fire, where most modern systems are sequential port. The ECM fires one bank of cylinders at a time, and there are two banks. Sequential port injection doesn't really become advantageous until you reach higher RPMs, but it's pretty much a requirement to meet modern emissions standards.
     
  16. IslanderOffRoad

    IslanderOffRoad Do you even lift kit? OT Supporter

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    That intake manifold appears to be a 4.0L Manifold, looks identical to the one in my XJ.

    I do know that the 258 manifolds can me massaged to fit the 4.0 head, all it requires is some shaving of the mounts due to the raised intake runners.
     
  17. aim2kill

    aim2kill New Member

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    i was wondering. i saw my buddy creation after the fact and had only a few details. he preffered to just show me wat it would do, not what it looked like :noes:
     
  18. Junkie

    Junkie re-tarded OT Supporter

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    I don't know why it's done on many cars, but on air-cooled motorcycles it's done for cooling. the exhaust side of the head needs a lot more cooling than the intake side, so the exhaust side goes on the front where it gets fresh air.
     
  19. P07r0457

    P07r0457 New Member

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    for a bike that makes sense, i guess, since many bikes are air-cooled.

    cars are almost always water-cooled. Furthermore, the exhaust needs to get pretty hot for the cats to do their job efficiently.
     
  20. deusexaethera

    deusexaethera OT Supporter

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    It's not entirely weird to put the exhaust at the front.

    1. The exhaust is more likely to fail than the intake, so putting it at the front makes it easier to reach for service.

    2. It keeps the exhaust away from the firewall, which keeps the firewall cooler.

    3. It allows the air coming into the engine bay to cool the exhaust manifold, and it heats the air in the engine bay faster on cold days, which is when engines run least efficiently, so it minimizes the amount of time the engine runs cold.

    It does tend to put the exhaust downpipe in the way of road debris, though -- I learned that one the hard way on my old Mazda -- but better to crack the exhaust than to crack the oilpan, I figure.
     
  21. P07r0457

    P07r0457 New Member

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    It costs more because you have more intake piping, and more exhaust piping. The pipes also must take more intricate bends, so that adds cost and complexity. The intake will become more heated, so you hurt efficiency, economy, and performance -- or you spend additional money on increased insulation.

    When the exhaust does fail, it's generally near the rear of the vehicle -- at the end of the tailpipe (rust) or at the muffer. Sometimes expansion joints will fail, but those are under the car, anyway -- usually near the firewall, even when the exhaust manifold is at the front of a transversely mounted engine. The point is that any time the exhaust system is serviced, you would have the vehicle on a lift, and the orientation of the engine makes little difference.

    and the point of that is what? The exhaust still runs directly under the floorpan, so you can't say it's a heat issue.

    Cooling the exuast manifold before the charge reaches the cats is actually a BAD thing.

    You can't say it's to heat the air intake on cold days because the exhaust isn't hot enough to really do so through convection on a cold start (pipes cold, engine cold, ambient cold). Besides, that's partly the job of the EGR system.
     
  22. aim2kill

    aim2kill New Member

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    true, theres no way the exaust is hot enough for this, and if it were it would be insane when the ambient air temps were high like during august or something.....
     
  23. Meph

    Meph itchy trigga finga niggas

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    Damn...

    The headers I bought do not fit. The won't clear the motor mount. I bought headers for a 4.0L MPFI thinking it would mate better with the intake manifold, but they obviously weren't meant for a '77. I'm going to have to pick up a set made for the '77 and hope they mate with the intake.
     
  24. affende

    affende Resident 4X4 Elitest Prick

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    in your balloon knot
    build your own??
     
  25. aim2kill

    aim2kill New Member

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    without seeing it..


    any way to finnagle it into place safely?


    if not, its a bummer, but nowhere near the end of the world. keep us posted:bigthumb:
     

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