I have come across an issue on my 67 where it seems the engine electrical harness comes loose at the firewall (which is behind the fusebox) Of course this causes the engine to come to a halt. The location of the plug is not in the friendliest place as it is tucked on the firewall below the power brake booster and towards the bottom of the firewall. I want to order a replacement small block engine harness that is set up for HEI. I am running a 327 with a manual transmission, the question is:
My car was born as a 6cyl, is the electrical harness going to be the same as for a small block and is the plug at the firewall going to be the same as it would be for a 327 or will I need to do a custom job here?
Also, the plug that keeps coming loose, does that have a way to secure it once attached like a bolt or a latch of does it just snap into place?

Again many thanks in advance for your insight.

 

I can't help on the wire harness conversion, but if I understand your question, there should be a bolt that sandwiches the fuse box and the outer plug together at the firewall. I have a 68' 327, so should be the same. Pic shows the bold head before removal and other is threaded hole at the back of the fuse box on firewall side.

 

WOW!,
I think I may be missing that bolt as the left connector seems to come loose once in a while.
So what you are saying is that in order to unplug either of the 2 connectors you first need to remove that bolt?
How does the bolt secure the connectors? is there a flange or some type of brace that keeps the both plugs connected or do they snap in?

 

Yes, once the bolt comes out, you unplug the harness from the back of the fuse box. Then this harness then slides apart in two halves. Those two halves don't snap together, but one slides out from the other. This bolt only goes through one, but when plugged in, this will locking the two together. Then screws in to the back of the fuse box on the firewall (as the photo shows). Sorry to don't have a pic if the wire harness pulled apart.

On the inside. the fuse box bolts to the firewall with two bolts (you see these two bolts protruding through the engine side of the fire wall shown in the photo on upper left corner and lower right corner of the fuse box).

If one side is coming out while bolted in (male plug side), then the slide grove is broken and you need a new plug. Arrow shows the location of the grove that could be broken allowing the plug come out.

 

I just got hime and took a quick look. Turns out mine is not like yours. Both harnesses seem to have a tab at the top and bottom which needs to be depressed in order to disconnect the harness. I will take a picture shortly and post it. By the same token I also confirmed the other question I had regarding what harness to order since my car was born as a 6cyl. As per Tech support at Year One, a small block engine harness is the same as a 6cyl. I will tqke picture shortly and post it just to make sure I am seeing what I am seeing, thanks again Turbo86.

 

Both connectors have the same thumb tabs at the top and bottom (2 per connector) and I see no place where a bolt or nut is anywhere between both connectors to hold them down. I should get the new harness this week and will swap it out in hopes to put an end to this connector coming loose.

 

Thanks for the feed back. You definitely got different connections. I did not know there was a difference between the 68 & 67 for the wire harness connections. I don't think they sell just those connections. If you want to fix it properly, looks like you may have to replace the entire wire harness for that plug? Good luck with your searching.

Or you could just zip tie the two together for now and hope someone here can help...??

 

So I received the replacement harness today. I disconnected the existing harness at the firewall and began to "disconnect and replace" at the same time so I do not get lost. Of course on a 54 year old car previous owners have taped off some of the wires as apparently they were no longer in use. The new harness looks pretty simple but even the simple things can get screwed up if you don't pay attention to details. I have noticed that a couple of the cables are not necessarily the same color as an example (old=orange and new=yellow). Funny that the harness I got from Ecklers said HEI ready yet it still has the connection for an old school coil and not a female spade connection. Each terminal is also not labeled even though the catalog stated they would be. I can make out the following connections - Master cylinder light, dummy oil, dummy water, Coil, Battery, Wipers, starting solenoid. I think I am all set but am looking for one of those dreaded wiring diagrams just to make sure I have not screwed anything up before I reconnect the battery.
Thanks again

 

So after a little bit of looking HOTRODDERS.COM (THANK YOU !!) ( https://www.hotrodders.com/threads/6...224344&slide=3) had the wiring diagram available and it covers the 7 connections I need to check.
Can't wait to get this in place so I can start putting miles on her.
Here it is for reference.

 

That's great news. Glad you were able to figure it out. Also surprised you got your parts so quickly, so that is good new too. Send pics of your car when you have time.