Blew up 87 350, transplanting with 85. stay tbi or not

[coyoteman]

Long story short, old hunting truck was a 85 1/2 ton with a mildly built 350 and 700r4 tranny. Broke the frame in half, so I had to upgrade. Bought a 87 1/2 ton with a 350, 700r4 and tbi. Well the replacement didn't last long, motor let go after a couple weeks. I am going to transplant the motor out of the 85 into the 87 so I need some info. First when I remove all of the tbi wiring will it screw with the tranny wiring for lockup? second, do I need to pull the fuel pump out of the tank, to run the 85 pump, or do I eliminate the 85 pump and run the other?
My other option would be to convert my 85 to tbi, but the tbi only got half the fuel mileage with a lot less power than the carbed motor, but we were going to put it on a scanner to check it out, can't now, lol. I know I'll need an adaptor or different intake to run the tbi, what else is there to convert the 85 to tbi other than that? Thanks

[1979C20]

I dont know much about what your doing, but I know you can and I would, piggy back the fuel pumps. Run the electric into the manual, incase one fails you have a backup.

[beastie_3]

I think you'll need a fuel pressure regulator to run a carb. Also, check your smog laws.

[slammed79]

Definitely check your emissions laws beforehand. It'd be a pain to go through the work then have to change it all.

[jthomas12287]

i have went through this process and it was much more involved than i thought it was still running the two stock 87 high pressure in tank pumps up to a bypass filter and regulator. contact kinsler fuel injection and they can talk you through what you will need

[topp]

I dont know much about what your doing, but I know you can and I would, piggy back the fuel pumps. Run the electric into the manual, incase one fails you have a backup.

Manual fuel pump is 6-7 psi, TBI is 13-15.  Won't work on a carb if you double up on the pumps.  You'll flood it out.

[coyoteman]

I can easily put in a tank off of an earlier pickup, have one sitting in the shed. My biggest concern right now is in 87 did they change the wiring to lock up the tranny as prior to 87. I will probably be able to trace the wires when I pull the engine out.
There are no pulution laws I need to worry about where I am at.
I would run the tbi on my 85 motor if I wasn't worried about the poor mileage it was getting before it let go, and it could be added w/o too much effort.

[Lt.Del]

ordinarily, tbi is much more fuel efficient than a carb.

[coyoteman]

ordinarily, tbi is much more fuel efficient than a carb.

Yes I know, but not this one, The tbi only got 5 mpg, and the carbed 85 was getting 12. My 85 motor is bored, vortec heads and has a mild cam, makes way more power than the stock 87 and a lot better mileage, I can also work on the carb. Both trucks were identical other than tbi. Both  mostly only driven off road.

[Grim 82]

My biggest concern right now is in 87 did they change the wiring to lock up the tranny as prior to 87. I will probably be able to trace the wires when I pull the engine out.

The trans should be plug and play. If you are leaving the 87 the same and just swapping the motor, the switches and wiring for the lockup will all be intact on the vehicle and you should just need to run a hose to the low vac switch on the firewall. I put a 700 from an 88 TBI suburban in my carbed 82, and pulled the wires and switches from the donor truck. It would have worked fine without the TBI business but in the end I had the trans rebuilt with a hydraulic lockup, so no wires needed.
For what you describe, I would prefer to keep it carbed as well, and run the mechanical pump and swap the tank like you said. I don't care for all the extra wires and gadgets and trouble codes and things, but that's just me. That said, typically TBI will get better mileage and have more hassle free drivability than a carbed motor, but only if it's working properly.

[coyoteman]

Thanks grim, thats what I was wanting to know.

[1979C20]

I dont know much about what your doing, but I know you can and I would, piggy back the fuel pumps. Run the electric into the manual, incase one fails you have a backup.

Manual fuel pump is 6-7 psi, TBI is 13-15.  Won't work on a carb if you double up on the pumps.  You'll flood it out.

 okay, all I know is my dad is doing that on his jeep. I dont know if one is bypassed or something but he uses both.

[beastie_3]

You should be able to remove the TBI pump and put in older sending units.

[VileZambonie]

Swap over the TBI stuff onto the new engine and keep it TBI.

[coyoteman]

Swap over the TBI stuff onto the new engine and keep it TBI.

I would do that but if I can't get the extra 5-7 mpg out of it as I get with the carb it's not worth doing imo. I still may give the tbi a chance on this motor if I can get the mpgs figured out. starting the swap tonight, so I'll do some looking into it. If I stay tbi can I get rid of the smog pump, etc? Cat has already fallen off. lol.