I have a destroyed 97 Civic DX (D16y7) with a working engine/auto trans.
I just bought a 97 Civic EX (D16y8 Vtec) blown motor (also automatic) but good chassis and body. Can I put the DX motor/trans into the EX and use the EX wiring harness and ECU or will I have to use the ECU/wiring harness from the donor car. I read the "sticky" on engine swaps but didn't see anything that went from a y8 engine to a y7 engine. Thanks.

 

Swap over the non-VTEC ECU from the parts car. Otherwise you will get a code when the EX ECU tries to engage VTEC and finds it is not there. The wiring should be plug and play since they are both automatic. You would leave the VTEC solenoid plugs on the EX harness unplugged.

If the Y8 head is still good you could put it on the Y7 block.

 

I kinda figured that but wasn't absolutely sure. Thanks for confirming that.

My goal is to see if the y8 engine can be rebuilt. If so, and not to pricey, I'll drop it back into the EX. Then use the DX donor motor/trans to find a car for my duaghter. The previous owner's daughter used Civic EX to get to school. Said she was driving and it suddenly stopped running. They thought it was a head gasket, I'm hoping it wasn't a timing belt. They said the car turns over, but won't start. So is a 97' y8 an interference motor (ie valves will contact pistons if timing belt fails)?

 

Funny I have an auto ex trans Im trying to convert to a manual.

 

y7 a/t needs y7 computer. the y8 harness would work since both are a/t, but unless there are problems with the y7's harness, why bother?

 

After I intall the donor motor and trans (non-Vtec) into the Civic Ex I'm just going to swap out the EX computer and put in the DX computer. That should get the car back on the road.

 

I know that swapping a y7 in place of a y8 seems contrary to honda enthusiast, but there is a method to my madness. The y8 has issues, either a head gasket or timing belt. I'm praying for the former not the later. In any case the y7 will get my son in a car relatively inexpensively and appears to just require the y7 ECU to work. If the y8 looks like it will live again, I will rebuild and reinstall it back into the Civic EX, then all will be right with the world once again.

 

I don't see an issue with dropping a y7 in as a replacement, I do however find it odd that you won't use the y7 engine harness to match the engine/transmission combo. You should be able to see what I mean by comparing the differences in both engines since you have them both.

 

Based off of mk378 comment earlier I should be able to run the y8 harness with the y7 engine. I just won't plug the Vtec stuff in. The y7 ECU, from the donor car, won't be sending Vtec requests on the y8 harness. So if this works as stated, why would I go to the hasle of pulling an entire y8 wiring harness out and installing a y7 harness outside of esthetics?

 

I appreciate all the comments before I dig in and start wrenching

 

because you'll have to peel the harness off of the y8 and put it on the y7, when you could just drop in as is. which sounds like more work to you?

 

Not only that you'll have to....screw it he'll figure something out.

 

Took me a moment but I understand what your saying now. Basically just leave the wiring harnesses on the respective engines and swap them with harnesses attached. Then plug then main loom back in.

 

boom!