TBI into a 77, need some help on some details

[77crewcab]

I am buying a 77 C10 SWB and want to swap in a 350TBI/700 combo but have a few questions on some small details ya'll might be able to help with.

1. For those of you that have done the TBI swap in an older truck, how did you mount the ECM? The older trucks don't have the brackets spot welded on so how do you mount it? Transfer the brackets or some other method?

2. This truck has dual saddle tanks. Can I use the TBI sending units from a burb/blazer tank? I would probably only use 1 tank until finding all the correct lines for the dual tanks and TBI tanks if need be.

3. The bed has been swapped for a newer one with the gas fill doors rather than the cap in the side of the bed. But they didn't swap the filler necks, so the origional cap in side of bed filler necks are just tucked inside the doors. Can I use the filler neck from a burb to fix this or is it too different from a pickup style?

4. How difficult would it be to put in a burb or blazer tank under the bed instead of the saddle tanks?

5. My donor for the engine/trans will be my 90 burb, so it has the electric speedo. Is there any reason to switch to a cable speedo? I have both style harnesses but kind plan on just taking the entire under dash harness from the 90 and swapping it to the 77. Any issues with that idea?

Any other issues I should be aware of?

Thanks for the help!

 

[dyeager535]

1. Haven't had to, but looking at the dash without the pad on, I think there is plenty of space to mount it. Most (all?) ECM's that vintage have bosses on various sides to allow mounting in different locations. A bracket would be pretty easy to make for this I'd imagine, and there are plenty of bolts already under-dash to secure a bracket to.

2. No you can't use the senders. Apparently the way the fill lines run is entirely different, and the depth is wrong anyways. A 1987 pickup donor (or new parts) is about the best you can hope to find.

3. No clue. I suspect you can't though, as the tanks are much further inboard on the K5/Sub.

4. Shouldn't be real tough, there was a short discussion on this earlier. Other than the straps that hold the K5/Sub tanks in place, the bedsides and bed are the same essentially...all the parts should swap over.

5. Absolutely no reason to swap to a cable. If I read your info right, your donor is a 2WD '90 Sub, so you'd want to swap everything, cluster, wiring harness, trans, etc., as I assume you plan to do.

My dad picked up the parts to swap TBI into his '73/81 truck, but the tanks/lines are the holdup now, since the dual tanks adds some complexity. His donor was a Sub as well.

 

[77crewcab]

1. Haven't had to, but looking at the dash without the pad on, I think there is plenty of space to mount it. Most (all?) ECM's that vintage have bosses on various sides to allow mounting in different locations. A bracket would be pretty easy to make for this I'd imagine, and there are plenty of bolts already under-dash to secure a bracket to.

So you are saying ditch the factory bracket and make some. Should be easy enough. I honestly hadn't thought of ditching the plastic factory mount.

2. No you can't use the senders. Apparently the way the fill lines run is entirely different, and the depth is wrong anyways. A 1987 pickup donor (or new parts) is about the best you can hope to find.

I already have -6 braided lines to hook up to a TBI sender, that I was going to use on my K5 before I sold it. If I found a TBI saddle tank sender I think I can use the braided lines. But I wasn't sure if the senders were different or not.

3. No clue. I suspect you can't though, as the tanks are much further inboard on the K5/Sub.

I'll have to go to the salvage yard and compare them I guess.

4. Shouldn't be real tough, there was a short discussion on this earlier. Other than the straps that hold the K5/Sub tanks in place, the bedsides and bed are the same essentially...all the parts should swap over.

Once I get it home I'll have to check on this option. I have both burb and blazer tanks so if I could use them easily I will probably go this route.

5. Absolutely no reason to swap to a cable. If I read your info right, your donor is a 2WD '90 Sub, so you'd want to swap everything, cluster, wiring harness, trans, etc., as I assume you plan to do.

Yes I am looking at using the 90 2WD burb as the donor. The plan so far is to use the engine, trans, rear axle, underdash harness, guages, steering column, and brake pedal assembly.

My dad picked up the parts to swap TBI into his '73/81 truck, but the tanks/lines are the holdup now, since the dual tanks adds some complexity. His donor was a Sub as well.

One other thought that occured to me. If I use the complete underdash harness from the 90, will the underhood headlight harness from the 77 work? Or am I looking at having to rewire the underhood harness?

 

[77crewcab]

Well update with good and bad. The deal on the 77 fell through, but an 85 C10 longbed took its place. It is running and driving. It makes things easier cause I have lots of front end parts for 82-87, I can even swap the 90 grill and everything. So I am left with mounting the ECM and getting the fuel lines and senders worked out (this one still has dual saddle tanks) But since it is drivable I can take my time getting things ready to swap all the TBI stuff over while still driving it around.

 

[dyeager535]

1985 should already have the bracket mounts in place...even without TBI, since ESC was used on some trucks they started mounting the ESC computer where the later ECM's mounted.