4.3 TBI to 5.0 TBI swap

[kevinr1970]

I think I have everything in order to make the swap but have some electrical questions.

I was told that the harnesses are the same but will need to swap the chip (or controler?). Can I just swap the whole box the harness plugs into?

For the engine (5.0) from the donor I just took the whole harness. This includes the external part of the fuse block on the firewall, the computer(?) mounted under the dash behind glove box and everything attached to the engine/alternator/starter.
Can I just plug this into the fuse block on the recipient truck?
If not, the recipient truck was two headlight and I am putting in a four headlight core. Will that portion of the harness/fuse block just plug in?

They are both '87 2wd trucks. The donor was a Silverado with all options and AC. The recipient is a Custom Deluxe with no options - no gauges (lights in the dash), no dome light, manual everything including tranny, etc.

Any help is appreciated. Thanks.

[87 STEPPER]

As far as the engine wiring go's you can just leave whats there from the 4.3 and install the 5.0 the ECM plugs should be the same id'e ck em before you do the inst. the only other thing to make sure of is that you use the 5.0 injectors in the TBI.

The wiring for the head lights are a stand alone harness so you should be able to just remove the old one and plug the new one in at the firewall connector.

Good luck.

[kevinr1970]

My only concern with leaving the harness there is it looks like on the 4.3 the starter wires go over the top of the engine then down the front. The 5.0 looks like they just come off the harness at the back of the engine, straight to the starter. I'll have to check this again to be sure. But if this is the case the wires might not be long enough?

I wasn't planning on taking the injectors off. They are in the TBI housing (for lack of better description) that resembles a carb right? The engines are both out of running (somewhat) trucks and are complete from pan to air cleaner.

I was thinking if I do not switch the harnesses I should at least pull the 4.3 harness with the engine. That way I can compare the engines/harnesses side by side. It might make it easier to pull it off the engine when its out of the truck?
BTW, the recipient truck is at my dads house and the donor truck is at my house so that is making it difficult to compare anything right now. I am bringing the engine to my dads house tommorow or Saturday to make the swap.

Any idea about the gauges? The recipient has lights and the donor has gauges. I would like to put the gauges and the whole dash cluster for that matter in to the recipient. Is the harness behind the dash different?
Better yet, maybe I can put in some aftermarket gauges under the dash and maintain the lights just in case???

Originally Posted by 87 STEPPER

As far as the engine wiring go's you can just leave whats there from the 4.3 and install the 5.0 the ECM plugs should be the same id'e ck em before you do the inst. the only other thing to make sure of is that you use the 5.0 injectors in the TBI.

The wiring for the head lights are a stand alone harness so you should be able to just remove the old one and plug the new one in at the firewall connector.

Good luck.

[87 STEPPER]

Kevin,

The starter wires should fit if you reroute them but im not 100% on that

And yes the injectros are in the TBI housing or carb if you will i didn't know if you were gitting a complete eng. or just a cob. so your good there.

I would agree with pulling the 4.3 harness and comparing it with the 5.0 but if you go that far ya may as well inst. the 5.0 harness in its place.

As far as the gages the wireing is all the same to drive them just the sending units are different for lights.

If you get the gage cluster from the same truck as the 5.0 it will have the correct sending units to drive the guages allready installed in the eng. the only thing that may be a problem is if the new gage cluster has a clock in it then what ever light is in its spot may have to be rewired to work on that cluster.

[kevinr1970]

Originally Posted by 87 STEPPER

...lots of useful info...

Thanks for the info. I've done a few engine swaps but never on anything that wasn't carb'd. I'm a little scared of the wiring but it seems pretty straight forward.
I guess we'll find out this weekend?
Thanks again.