Good evening, new to theforum. Working on a '70 K-5 Blazer. Need to removet he doghouse for an engine swap. Wondering what the secret is to removing the pins from the bulkhead disconnect instead of just cutting the wires. Thanks in advance.

 

This will depend on the type of electrical connectors used. A service manual will list the type. For instance, in the late 90s they used Metripack of different sizes. They also used what are called Packard connectors.

You might have luck using a guide like this:
Understanding GM’s Most Common Plug Options https://share.google/TvQc1Hht6vyXMC5g0

Then once identified, you can find the tool or technique to disassemble the connectors.

 

I believe that on your truck, the design of the harness is such that the entire harness can pass through the firewall once it is disconnected and removed from all of the connection points underhood (mounts, grounds, accessories, etc.) and the bulkhead connection is unbolted from inside the truck.

From there, if your goal is to rewire for a new engine, you'll need to follow Christine's advice and determine the connector type.

 

Thanks for the help. The goal here is to separate the harness for the front end (headlight, etc) fron the bulkhead disconnect in order to remove the doghouse without cutting any wires. It appears fron the lik provided that these may be Packard connectors. Apparently there is a tool to slip along side the connector males to release them from the disconnect body. I have attached a picture so we can see if we are on the same path. Thanks in advance for your patience.

 

The male ones might come out by pinching the blade with some needle nose pluers to make rhem more narrow. But for the female ones you likely will need a skinny probe type of tool to remove them.

I bought such tools from this place but for my Metripack connectors. It looks like they have several types of tools for the Packard connectors.


https://terminalsupplyco.com/Store/D...ATDRILL=DEL120

 

The specific type of connectors in your truck are Packard type 56 & 59 terminals and can be identified by the size of the spade on the male side. The type 59 terminals would be for higher amperage circuits compared with the type 56 terminals. A quick measurement of the male terminal would tell you which you have. The image below gives better context in to the makeup of the terminals themselves and their retention methods:

ebay image from a google search for packard 56/59 terminals

The image above does not show the tang on the backside of the female terminal that the available disconnect tool is designed to release. There are videos online that show the process for getting these apart as well.

On the male terminal, you need to push in on the side of the spade that has the retention tang on it until it clears the ledge in the connector body freeing it from the body. The retention tang is the free leg as can be seen in the image above. My initial thought is to use a few small screwdrivers, one to push in on the tang and another to push down on the terminal. Some words of caution though... Removing the male terminals should be done with great care so as to not damage the connector body. The only thing that keeps the terminals in place for proper terminal insertion depth is the plastic of the connector body itself. If it is damaged during the removal process, contact in the mating terminal would be compromised.

Before reassembling the harness, you will need to spread the terminal back out so that the tang can catch again and you may need to spread it a bit after it is re-inserted into the connector. The initial spread can be done with a small screwdriver. If it is necessary to do an additional, after insertion spread, a small 90deg or hook pick could be used to accomplish this.

I am not fully following you on what the reasoning is for separating the harness is and I really do not have to, but I am trying to give the best advice I can to keep problems from occurring unnecessarily. If you are modifying things, then by all means get after it. If you are just taking things apart and putting them back together again, this form of disassembly can often cause problems down the road on stuff this old. I still would try to remove the harness completely. The plastic harness clips are available for pretty cheap. I'm not so sure that a new connector is...