Engine Bay Wiring & Vacuum Line Installation

Now that the front clip has been installed back on the Corvette, and most of the trim features fitted in place, my attention turned toward reinstalling all of the electrical harnesses and vacuum lines in the engine compartment. To say this was a challenging task would be an understatement – it was like putting together a giant 3D jigsaw puzzle!

I can’t stress enough how important it is to have a good photo record of how everything was installed before you disassembled it. In addition, I recommend tagging every connector and component using an index card and zip tie with a brief description and photo number on each tag as outlined in my tech article “7 Simple Car Restoration Tips“. I’m convinced that this practice was a huge part of my ability to successfully complete this task. In my opinion the illustrations in the Corvette Assembly Instruction Manual (AIM), and the other manuals I have, just aren’t detailed enough to allow the wiring harnesses to be reinstalled without photos.

That said, as is often the case my work started by cleaning up what came off the car. In my case the harnesses were caked with dirt, grease and grime and were also covered with overspray from a past paint job gone wrong. Here’s an example of what I started with:

Following a cleaning using good old soap and water I set to work cutting away the old tape. After thinking about it for a while I decided that replacing the tape was a much less daunting task than trying to clean it. To keep the wires properly aligned I did this work a little at a time. I would remove several feet of tape, clean the wires using a rag soaked in lacquer thinner, and then wrap new high quality electrical tape around the wires. It was a tedious process, but it worked well.

Keeping the tape tight and the wires bundled tightly together are important as you re-wrap the wiring harnesses. Also, try not to leave any ends of the tape exposed. If you have to cut the tape for whatever reason (I tried to avoid it) when you start wrapping again run the tape back over the starting end of the tape so that it doesn’t unravel over time. I also learned that, while it’s good to pull the tape nice and taught as you wrap the wires, it’s best to use very little tension where you end and cut the tape. If you stretch the tape near the cut ends the tape will pull away and come loose over time. Leaving the tape slack at the ends will provide a better seal and will make the end less likely to come unstuck over time (learned this from experience).

Once the wire harnesses were cleaned up and taped I realized that the factory-installed rubber coating at the fuse block was very deteriorated exposing many of the wire ends and terminals. To resolve this a bit of liquid electrical tape was applied to the fuse block to get everything sealed up nice and water tight. It worked really well. You can buy liquid tape at most hardware or home improvement stores.

  

And here’s the finished product – just one of several wiring harnesses that needed a lot of TLC. I found that maintaining the tags was difficult during the cleaning process so I actually ended up temporarily removing them and reinstalling them one at a time while the harnesses were cleaned. It was a lot more work to do it this way, but when it came time to install the harnesses I was thankful to have the tags as a guide.

Obviously there are many components under the hood that the wiring and vacuum lines connect into so I spent some time cleaning up those items too. These included the windshield wiper motor, wiper door actuator, coolant reservoir, vacuum reservoir, and windshield washer bag. Obviously not all of these are included in the electrical and vacuum systems, but installing them before all those wires and hoses went in seemed like a good idea.

         

Once everything was cleaned up and ready to go I set to work installing the wiring harnesses and getting the wires routed. The first step was to install the fuse block on the interior side of the firewall.

Once installed I applied some dielectric grease to the terminals and bolted the engine-bay side of the harness in place. This is when the “fun” really started…

Initially I roughed out the routing of the wiring and vacuum hoses, positioned them where I thought they went, and  verified all of the wires and hoses could reach where they needed to go. This actually took quite a while – even using the tags and photos I had. There was a lot of trial and error to the process.

This is how I spent about six weekends over the course of the summer – examining photos, connection details, routing paths and other relevant information visible in the hundreds of wiring photos I had taken. Again, having all of these photos was a huge help!

One thing I noticed in my photos was that the headlight vacuum relays were mounted directly to the hood surround header bar when I bought the car. However, at the factory they were mounted to a metal plate which was then bolted to the header bar. This plate positioned the relays closer to the nose of the car and helped to hide the relays and associated tubing. I was really striving for a clean installation here so I fabricated a new plate out of some plate steel that was laying around my garage.

  

After about an hour of work I had a replacement plate finished and ready to go.

Many hours and countless zip ties later here’s what I ended up with. The routing scheme isn’t quite factory, but I think it’s a clean arrangement. For instance, I tucked the wires behind the windshield washer motor, used many zip ties to keep the wires and hoses bundled together, and did my best to keep the arrangement very compact. As a result there are now some J-clips that really don’t serve much of a purpose now. I’ll probably end up removing those before dropping the body onto the frame since their function has been replaced by all the zip ties that were used. Note that the various hanging wires and hoses connect to the engine so those have been left as-is for now.

Ignore all of the dust. I forgot to blow everything off before I took these photos.

      

I was surprised to see how well the wires cleaned up. Soap and water hardly put a dent in the grime, but a lacquer thinner soaked rag worked really well.

   

Note that I used plastic zip ties instead of the original ties. Zip ties are cheaper and less visible in the finished product. Just don’t over-tighten them on the vacuum lines or you’ll pinch the lines shut and the headlights will operate very slowly, or not at all.

I spent quite a bit of time dealing with the wires and hoses near the nose of the car. I really didn’t want to see them so I worked hard to get them hidden. Notice that I got rid of the original plastic ties along the header bar and used some rigid plastic clips instead. This allowed me to tuck the wires tight to the underside of the hood surround and then bolt them securely in place. This worked great and came out looking really clean!

Some shots along the passenger-side fender. These are mainly air conditioning components. The installation of these will be covered in my next update (consider this a sneak peak)!

  

This area was a real challenge. Hoses, wires and lines everywhere! I must have tried tweaking the arrangement of the lines 20 different ways and went through a ton of zip ties in the process – route the lines, zip tie in place, view the result, decide to tweak it, cut the zip tie, repeat. All in all I think it came out well though.

 

And there you have it! The wiring harnesses and vacuum lines installed and ready to be connected to the engine – one more update done and in the books. In my next update I’ll be documenting how I retrofitted the original Freon-based air condition system to work with R134a refrigerant and the installation of the various heating and cooling lines. Hopefully I’ll have the next update posted by years end. If you have any questions on the routing scheme I used for the vacuum lines or wiring  harnesses feel free to post a question over on the Corvette Restoration Forum and I’ll do my best to provide an answer or additional photos. Also, if you haven’t done so already, please Like this project on Facebook to receive additional progress updates and notifications when updates have been posted. The page has nearly 800 likes so far and growing – wow!