Spuddering motor
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
You can't change the firing order without a different cam. Both firing orders work on the same small block bottom end - you can put a 351 cam or a 302 cam in a 302, and change nothing else internally, and it will work. The only difference in the mass air swap that MustangGT did is the injector firing order in the computer.
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Post Fiend
Joined: Nov 2001
Posts: 14,947
Likes: 6
From: Topsfield, MA
Originally Posted by lexluthr69
Just put your plug wires back to the non-HO firing order and fire it up. You should immediately notice correct firing, but MABYE with a slightly rough idle.
I put the plugs back as I said and it runs ok. You were correct, after some seat time I noticed the idle was a little rough. I'm going to swap the pins on the computer connector to get it right. Even as it is now it runs smooth and has more power then before, can't wait til the SEFI is working correctly.
Talyn, ya don't have to change the crank/pistons to change firing order.
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
It should feel a whole lot better when you get the injectors right. The throttle response will be incredible.
Eric Poe North Carolina State University class of 2006 (if all goes well).
(jeez where you guys come up with your names!)
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Post Fiend
Joined: Nov 2001
Posts: 14,947
Likes: 6
From: Topsfield, MA
Well I took the connector off the computer to have a look-see. It doesn't appear that I can just pull the pin out and swap the pins (this is the MAF kit's connector I'm looking at). There are two groups of wires going to the connector. One appears to be for the MAF sensor, and the other for the injectors. The wires going to the injectors have a piece of tape on them that tell you what pin # it is, so I know which wires go for which pin #. The only thing I think I can do is cut the 3-5 injector wire at the beginning of the harness and swap them, solder them, and heat shink them. I don't know if I want to do this not knowing if its going to work correctly, and when I'm going to have to swap this back in a few months. It runs ok but the idle is a little weird. It runs fine for a little while but after a minute or so the idle goes a little lower in RPM and it is a little rough. I can live with it for now though.
Hotshot
Joined: Oct 2003
Posts: 17,799
Likes: 103
From: Ashland City, TN
if gas fireing in at wrong times though. you got gas setting in the chamber waiting to be fired on some pistons. Thats why its idleing rough.
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Post Fiend
Joined: Nov 2001
Posts: 14,947
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From: Topsfield, MA
I can take one when I get a chance. Basically it's a two sided plug. One end goes into the computer and you plug the original truck's harness into that. So basically the kit's connector is sandwiched between the computer and the original harness.
Lead Driver
Joined: Nov 2002
Posts: 9,557
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From: Concord, NC
I wish I knew how to get those things moved around, but I'm not familiar with that sandwich adapter for the motorsports conversion. It might be best to just drive it like this for the short time until you get the new motor up and going so you can avoid cutting and soldering the wires twice. It shouldn't be any problem doing that as long as you make a good connection, but if you're gonna have to turn around and put it right back like it was, it might be better to just leave it be for now.
Senior User
Joined: Jan 2003
Posts: 383
Likes: 1
From: Newport News USA
Eric, weren't you part of that conversation we had with TripnDrag about the swapping of the injector wires around? Talking about how he's running the HO plug firing order with the regular 5.0L injector order in SEFI. Whereas, I cut and spliced/soldered mine to match HO plug order with HO injector order. I did the cut and splice, but I did mine knowing that I wouldn't be going back to the old firing order.
Basically the only place you'll see a difference is in your idle and out the tailpipe. Once you get back to true SEFI and both firing orders are in time, your emissions will be cleaner and your idle will smooth out. The FRPP tech guys told me over the phone that once you hit 2500RPM it doesn't really matter as the injectors are firing at such an extreme rate that there's not enough time for the fuel to just "sit" there.
If you plan to run it later with the order it's in now, just leave it be, and you'll be fine.
Basically the only place you'll see a difference is in your idle and out the tailpipe. Once you get back to true SEFI and both firing orders are in time, your emissions will be cleaner and your idle will smooth out. The FRPP tech guys told me over the phone that once you hit 2500RPM it doesn't really matter as the injectors are firing at such an extreme rate that there's not enough time for the fuel to just "sit" there.
If you plan to run it later with the order it's in now, just leave it be, and you'll be fine.
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