Hello everyone,

I currently have a carb LG4 305 in my 87 base. However, one of the previous owners modified it so an HEI distributor could be used and the carburetor is a Q-jet from the 70s, so it is not computer controlled anymore. Also, VATS is non functioning as well (as a result of the tampering maybe?). I believe it was converted poorly since my engine bay looks like a rat's nest, but I have a chance at getting a L98 TPI with a rebuilt 700R4 for cheap with the wiring harness, gas tank, fuel pump, lines etc., basically "everything" needed to run. And it has been tuned as well.

My question is, has the previous modifications done to my car complicated this swap? My situation seems to be unique since I haven't really found any answers besides changing the fuel delivery method with the same motor, or engine swapping with the factory wiring. I just want to know if it's feasible to do this swap under normal circumstances, and then with my situation.

Thank you!

 

If you have everything for the L98 it doesn't really matter what's in your car...

 

I've heard that the engine wiring harness just needs to be replaced and plugged in to where the LG4 one was before, but there aren't provisions or pins for the fuel injectors, etc of the TPI. That's what I was wondering if it would be a problem or not? Yeah I have the whole setup, but how compatible would it be with the rest of wiring in the car? Sorry im not really clarifying, im still new to this

 

It really depends upon what's been messed up under the hood. A good portion of the wiring is for the engine & ECM, but there are also chassis harnesses under there, which probably won't come with the TPI set-up.

Most likely, though, the first response you got is correct. '87 should have an in-tank electric fuel pump, so that harnessing should be there. The mess is probably associated with the ECM harness that goes into the passenger side fenderwell, which will be replaced with the TPI ECM harness.

 

The guy is offering me the whole car for not much more so I might just tear out my 87's complete wiring throughout the car and replace it with all of the 88's. Would that be easier than trying to connect the TPI wiring and ECM to the rest of my existing wiring? I read the pin connections do not match if I do it this way. Also,i believe the speedo cable on the 88 is electronic and my 87 is mechanical, so I would replace the dash and associated wiring anyway. What do you guys think about that? Thank you again

 

Is an 87 with LG4 equipped so a higher psi pump is all that's needed for TPI as far as fuel lines (firewall-back) too?

The 87 ECM harness is standalone where the 88 is routed together with the chassis harness. There are very few birds with mech speedo in 87.

So if you pull the 87 ECM harness, you'll be able to see how few differences there are at that harness and the dash connectors (many are the same). It will help you decide whether to go through with your whole-harness plan, or to just swap over the TPI required section only. You're in for work either way but are on the right track.

 

Why bother? 87 didn't have VATS. If the car is already carbed, just run the carb on the L98 and skip the TPI. The wiring rats nest is easy to clean up, just remove the old computer controlled ECM harness.

You could convert to TPI, it'd be like any other TPI swap, it's just a lot of work just for EFI. The carb would run just as well if it's setup right, and probably make more power than TPI.

 

I agree with Drew. Lot less hassle Probably lots more power also.

 

No, the pump would have to be replaced.