Hello all. First post. I apologise if this is in the wrong spot. If an admin could move to a better suited place that would be greatly appreciated. I recently started rebuilding a basket case I bought from a buddy. Car was originally a V6 Berlinetta or so he says. I don't have the front end and never ran the rpo to verify. Anyways the car is a little of this a little of that. Originally had V6 auto with air. Now I was planning on keeping the air until I got frustrated and cut the entire harness out. The system was open for so long and half missing that it wouldn't have worked anyways. Now I'm running a carbed 350 with a T-5 and an HEI. I cut all the wiring out of the car with the exception of the C100 connector. I have my pin outs and am planning on building my custom harness to retain gauges off of it. I was wondering if I could find a hefty source to power my HEI off the ignition side of the fuse box through the C100 connector. Has anyone done this? I know they require a lot of power and would be unsure how else to power it without adding a separate switch. Any and all help appreciated. Thanks!

 

Assuming you're talking about the old large cap HEI, you need a good power source to feed the coil. Should be at least a 12 gauge wire through a switched power source. A fused circuit with a 20 amp fuse is recommended.

 

Since you didn't cut the wires to the C100 connector, the wire is already there. It's a pink, 12 gauge wire. If you did cut it, it would still be on the other side of the firewall coming out of the other connector. What you need is a C100 diagram that tells you what wires are for what...

 

Thanks for the quick responses guys! I did cut the C100 back to about a 2 foot lead. I still have all the wires coming from the connector tho. I see where there is a pink wire that said computer command control and mpi control. It's in cavity F4. I believe this is the wire you are talking about? I am not at the car unfortunately so I'm unsure if it's a 12ga wire. Thanks.

 

There's a smaller pink w/ black tracer, which is probably the one you found There's also a solid pink ,large gauge, which is the one you need.

 

F4 is the wire for the coil on almost, if not all, cars. It is unfused and powers the coil directly, go for it

 

Scooter are you being sarcastic or serious? Maybe my diagram is wrong for my year car?

 

Not sure why you would think I am being sarcastic. I have the books for all the firebirds from 86 and up, I think they all show that F4 is the pass through in teh C100 for the coil wire. It is one of two unfused circuits in the car, that's the one you would want to power your HEI with. The circuit protection is the fusible link at the starter for that and the headlights.

 

F4 should be the wire you need

When you see it, its a very large pink wire

 

Sorry Scooter. Hard to decipher through txt. It just threw me off when you said it was not fused. I was unaware it was fuesable link protected. I appreciate the help.

 

He is quite right about that, you know.

Doesn't matter what shape the fenders are pushed into, how many doors it has, how many passengers it seats, how many cylinders are in the engine, ... ALL cars have certain electrical things they need. Battery feed into the cabin, ignition from the switch to the coil, headlights, turn signals, temp oil & charge indicators, etc. etc. etc. GM makes that bulkhead connector pretty damn universal, so that they don't have to re-engineer it from a clean sheet of paper for every car. You might be REAL SURPRISED at just how universal it is.

The battery feeds INTO the car are fused with fusible links, at the source end (big starter terminal). There is no fuse between the ign sw and the coil: its wiring depends on the source FLs for protection.

 

That's good to know. I can imagine how many cars use that same set up. Its definitely cost effective. Now that big pink wire going to the coil is protected by one of the red primary wires feeding into the fuse box off if the starter correct? It basically bypasses the fuse box and is ignition controlled? So correct me if I'm wrong if I lose the FL on the starter (that controls the pink wire) I could lose the pink power and some of the fuse box?

 

That is exactly correct.

There are 2 Big Red Wires (at least) that carry power from the battery to the entire rest of the car. Each joins the battery at that starter post, and has a fusible link in it. They used FLs (pieces of wire) rather than physical "fuses" because they're SO MUCH more reliable... sure, they go bad, but it beats the crap out of constant intermittents, bad connections, burned up sockets, etc. that would result from trying to do that with a fuse. The FLs are there really only to protect the wire; they're generally 3 - 4 gauges smaller than the wire they protect. They're made out of wire that the insulation won't melt when it gets hot, but rather the conductor inside will.

Each of the 2 Big Red Wires powers about half the car. In fact, if you look closely at the ign sw wires, you'll see that there are 2 of them there; each powers about half of the load controlled by the switch. For example you might find something like that the ignition and starter solenoid end up getting powered by one, and the accessories like radio, HVAC, etc. are powered by the other. Likewise, the headlights (and tail and dash lights) are all on one, and the brake lights and turn signals on the other. Don't quote me on the details but it'll be something like that. If one FL blows, about half of the car quits working.

And yes, the pink Ignition wire goes straight from the switch to the coil through C100; doesn't pass through any fuses. There are other things run off of the same ign sw contact that DO go through fuses; the gauges for example.

 

Thank you so much for that explanation. Wiring isn't so much my strong suit haha. I needed up taking my jumper and powering the 2 wires and low and behold the car came to life. I need to sort my grounds. The light chime was on and the right marker was on and the gauges jumped when I hit start. The brake light and seatbelt lights worked. I assume there are chassis grounds as well as frame to body and engine. The one thing I thought weird was no grounds in the C100 plug. I assume there has to be a shared return for the reverse light switch and other 2 wire sensors on the engine. I know coolant temp is one wire but I believe oil pressure is 2. I will be running e fan as well and I'm sure that I will need to get a separate controller for that and somehow power it from the C100. I'm thinking of doing a relay control set up similar to factory. I have a few HID headlight harness that are already built for similar purpose.

 

I just wanted to post this up so you can see what they mean by "big pink wire." The small pink wire with the white wire go to the HEI module in the small cap distributor. The large pink wire is the one you're looking for and the white wire with the connector on it is for a tach in this case. It sticks out like a sore thumb in the harness.

 

Awsome! Thank you for the clarification. I was wondering if I could just hook the tach sense up to it with no issues. I do have a small cap HEI distributor. I like the big cap as less parts and a cleaner appearance.

 

The factory uses a little "tach filter" in the white wire, to keep ignition noise from being a problem, no doubt... looks alot like the condenser that does inside a disturbutor, butt has a wire coming out of each end.

 

Sofakingdom where is that located? Behind the dash? Thanks.

 

On the firewall, usually right above the distributor.

 

Ohh really. My engine bay was stripped when I got it. Don't remember seeing anything like that in my pile of stuff. Will it be ok without one until I get one? Thanks

 

Sure, it'll work, just may have noise in the radio or the like.

 

Ohh ok. That's fine. I need to figure out if I'm gonna run my tac from the HEI or from the 3 wire alt I have. I don't know which would be a better choice?