2.8 TBI is seized, upgrade or replace?

[hoosierloser]

I just bought a little GMC s15 truck 87' year model. the crankshaft wont turn over at all, I really would like to upgrade to something bigger right now, mainly to the 3500 I already have sitting around. The only thing is I dont NEED the extra power right now it would be more of a want. I really just want to get it running for a good daily driver.

Has anyone upgraded to a 3.4 or 3.1 rwd block in one of these? Does the harness, fuel system, top end and computer have to come with the donor engine? I have started pulling apart the engine for removal, just bought the truck 5 days ago but the wife is sensitive about having vehicles that dont move under their own power so the sooner I can decide what I want to do and execute the plan, the better.

I have watched on this site for awhile, but it will be the first time I got my hands dirty on one of these.

[Guest]

Yep, externally the RWD (gen1) 2.8, 3.1 and 3.4s are all the same. You use the 2.8 fuel delivery, intake, dizzy, etc on the 3.1 or 3.4 and it bolts right in.

[hoosierloser]

Ok thats good to know. The exhaust manifolds on the 2.8 look pretty tiny looks like they would really limit a 3.4

[IDCavalier]

I'm sorry, but I don't understand what you are doing. Not that it matters much, IDK how much help I would be.
Are you going to put the 3500 in your truck with the 2.8 tin on it? Is that an LX9?
You mentioned a 3.4. Is that the motor you are going with? I have a RWD 3.4 in my 1994 Camaro and I will be swapping in an LX5 Olds motor in soon, so maybe I can hopefully provide some insight as I remove it. Pace Setter makes headers for the 3.4 'maros, but they're a little expensive.
This sounds like fun! I will try to help if I can...

[hoosierloser]

The 2.8/700r4 came out and the crank has spun main bearings. I'm going to swap in the 3500 now not later. I have a '7730 ecm and i just picked up a LX5 throttle body from the pick n pull. Now I just need to clean things up and start mocking up the 3500.

[Guest]

RWD 3500 ftw!



(It is an LX9, I just used an LA1 UIM to make the swap easier, since I was in a time crunch.)

[hoosierloser]

Thats a pretty nice setup there, this one will probably stay n/a though. I was also looking for engine harnesses at the pick n pull but found almost no early 90's fbodys
or j bodies. Is there a complete list of donor vehicles that used the 7730 from the factory?

[hoosierloser]

Was searching around and found a list of vehicles with 7730 heres the link http://www.thirdgen.org/forums/diy-p...plication.html

[neophile_17]

You will probably find it easier to re-pin your stock harness than to start with a FWD harness assuming your truck is EFI and the harness is in decent shape. The connectors use the same pin insert, you just need a heavy duty paperclip to remove them, then insert into the 7730 connectors. You still need the computer, connectors and a couple extra pins. I just grabbed the computer, and cut the harness with 12-18" of wire. If you see a 2.8L or 3.1L FWD from about 87-94 then there's a good chance it's a 7730 but verify that before you shell out the cash. Smart phones make JY parts hunting so much easier.

Sam

[hoosierloser]

Got the 3500 tore down. Found #6 rod bearing badly damaged. A little damage on the #3 main bearing also. Guess this free engine is going to cost me some money.

Responding to Sam, the truck is TBI and only had 2 injectors, I wish there was a way to use the factory harness but it doesnt look like there will be, and I would like to use the DIS ignition of the later models. I am planning on installing a 7x crank wheel from british car conversions while I have the crank out.

[caffeine]

Ive repinned an iron duke TBI harness to a 7730 with DIS. It really wasn't bad

[Guest]

I'm torn on which way I'd go harness wise. While I could make the TBI harness work fairly easily with a '7730 and DIS, I always hate soldering the wire that is used for the injectors in TBI harnesses. I think they used aluminum wire for the injectors for some reason. It's also missing wires for the MAT. Other wires could be re-purposed for that duty, if you're not using an EGR, but if an EGR is needed, well, then the wires for the MAT are still missing.

It also wouldn't be that difficult to swap in a FWD harness, open up the hole for the bulkhead passthrough, and modify the harness to fit. Regardless of which harness is going to be used both will take modification to make work.

[hoosierloser]

Ive repinned an iron duke TBI harness to a 7730 with DIS. It really wasn't bad

I didnt even think that this was an option. Do you have to add entirely new circuits the length of the harness? If you had a writeup on this I may try this route.

[neophile_17]

I did a similar thing as caffeine. Because the 7730 uses batch fire (2 sets of 3 injectors in parallel) you have the correct number of injector circuits. The way DIS works is (crank sensor)-> (DIS Module)<-> (7730). Use the same signal for tach and timing that your old HEI used. I haven't seen a writeup. This is as close as I've found http://www.gmtuners.com/files/Fiero_2.8_to_7730_$88_DIS.pdf and since it's for a Fiero it's probably only about %85 applicable. Just have wiring diagrams for both cars and get started, it's pretty straight forward but attention to detail is required. Raven is correct that additional wires are needed. I don't run AC so I re-purposed that wire and fed 2 more through a bulkhead fitting.

[caffeine]

I could probably make you a Re-pinning spreadsheet if you decided to go that route.