CODYZOOMZOOM Posted February 3, 2014 Share Posted February 3, 2014 So im trying to figure out what to to the engine has 150,000 on it and I paid $200 for it is the dual intake runner style head how hard is it to swap and splice the harness to run the mpfi? Kinda bummed about the whole thing Link to comment Share on other sites More sharing options...
ruparts Posted February 3, 2014 Share Posted February 3, 2014 So im trying to figure out what to to the engine has 150,000 on it and I paid $200 for it is the dual intake runner style head how hard is it to swap and splice the harness to run the mpfi? Kinda bummed about the whole thing hi, the mpfi is not going to run with a spfi controlled fuel system. the only way to make use of the motor is to swap out the heads& intake,, use your original heads and intake manifold with "all it's original wirring",, basically use all the original stuff except the shortblock( crank/rods/pistons/ engine case). the rib belt pulleys are optional,, but the alternator and a/c compressor and all belt driven pulleys will have to match. also the water pump might be different, there are 2 ,, 1 is 105mm flange height the other is 110mm flange height.. both fit the motors, but you need the right one to match and line up for the pulleys to align.. the ehhaust is the same, use your original. ** if you bought a turbo mpfi motor,,, then you really should just forget it,, the low compression would be very unsatisfactory for use without the turbo and just changing the heads/manifold won't alter that. the up side is, a normally asperated mpfi motor will function great with your original heads and manifold ,accessories etc mounted on it,, and you would have fresh head gaskets on there,, that would be my advice to do if you want to use any of the motor you bought,, otherwise you might find another spfi motor and trade, or sell this one and buy that one etc,, but in my opinion trying to change the cars wiring to make an mpfi work is going to turn out badly , i never heard of it being done successfully anyway, all the vehicle system is wired to run spfi is the problem,, not just the motor wiring,, the motor harness is just the tip end of the whole thing. Link to comment Share on other sites More sharing options...
wagonist Posted February 3, 2014 Share Posted February 3, 2014 Just spitballing here as I've never seen a SPFI motor (Subaru never bothered selling them here, and kind of rightly so in my opinion ), but could the SPFI throttle body fit to the MPFI manifold? Then just use the SPFI wiring, etc leaving the MPFI injectors fitted (to seal the holes), but unplugged. Link to comment Share on other sites More sharing options...
ruparts Posted February 3, 2014 Share Posted February 3, 2014 (edited) hi, maybe it could fit but as mentioned the entire system is designed to run 4 injectors and it just won't do what you are thinking. ( Hi , i was wrong here, his original car is spfi so the system does not run 4 injectors, for some reason i was not thinking correctly when i posted this originally, corrected 2-4-14) Edited February 4, 2014 by ruparts Link to comment Share on other sites More sharing options...
Uberoo Posted February 4, 2014 Share Posted February 4, 2014 no use the SPFI throttle body and wiring harness. Link to comment Share on other sites More sharing options...
wagonist Posted February 4, 2014 Share Posted February 4, 2014 why not ruparts? Using the SPFI wiring, sensors & throttle body (which I'm guessing has the SPFI injector in it) & not having the MPFI injectors connected to anything (plugging up the fuel line hole), it'll just run as a twin port SPFI. Maybe need to change over the MPFI distributor for the SPFI also (I don't know enough about the SPFI to know if they're the same or not) If blanking ports existed for the MPFI injectors, then they could be removed altogether. Link to comment Share on other sites More sharing options...
WoodsWagon Posted February 4, 2014 Share Posted February 4, 2014 The turbo intake manifold could probably have the spfi throttle body adapted to it but the xt should have come with the "spider" intake thats more like the EJ ones. Not so easy to adapt. Link to comment Share on other sites More sharing options...
ruparts Posted February 4, 2014 Share Posted February 4, 2014 hi, i sort of got this wrong, maybe. the car he is wanting to put the motor in has spfi system yes? so if a straight up style intake for the mpfi heads could be fitted with the original spfi TB and all the original wiring & sensors, it might work. as mentioned the 4 injectors would be inert, the original TB and sensors all back to like original, it might work. they did change the TB around 89, they have more wires in the connector,, the main thing here is,, use the original TB and and wiring! adapt the TB to fit the mpfi manifold, in theory i agree it should work. just for information in 85 year model they offered a mpfi engine that was a normally aspirated , non turbo, option for sedans and wagons, after that all the dual port heads came on turbo motors , except the ones on xt's , they did have a NA mpfi with a straight up style TB, and also a turbo mpfi with straight up TB. in late 87 the spyder manifold was introduced on the mpfi motors, pretty sure those were only on xt however. but there are plenty of the early style straight up TB mpfi manifolds around, all of the 85-87 ones could be used to try this. 1 Link to comment Share on other sites More sharing options...
turbosubarubrat Posted February 8, 2014 Share Posted February 8, 2014 You could get the wiring harness for the engine and dash out of the xt along with fuel pump and ECM. Then splice the harness out of your spfi with the mpfi where need and put the fuel pump and ECM on so you can run this. Link to comment Share on other sites More sharing options...
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