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Old 10-13-2010, 11:16 AM
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Pontiac 400 wiring question

I'm back again.. but I'm really close to starting this engine! So, when I was disconnecting everything to take the old engine out, I removed 2 wires from the HEI distributer. These wires came from the car not the distributer base, and I'm pretty sure they came from the same wiring harness. I think mentioning the color is pointless cause the wires may not be original, but they were green and yellow. After I got the new engine in (I transfered everything from the old engine to this new long block, including this HEI) I noticed that I only had 1 wire to put to the HEI . I have not misplaced that wire, I am 98% sure that I ripped it out of place when lowering the new engine in. Im looking at the harness that I think it came out of. there are 10 wires. 4 go to a black box on the middle of the firewall. 1 larger red goes to the alternator (bat). 1 goes to the electric choke on the carb. 1 dissapears down to the tranny, I havent followed it all the way yet. one has a female conector on the end with a protective rubber sheild, it's blue, and It's really oily and dirty, I think it may have been the original oil pressure sensor wire, IDK, there is an aftermarket one now and it is attached to the oil filter housing. Finally, there are 2 wire crimped together with a crimping tube, and it looks like they both were feeding a single wire. I am thinking that this is where my missing wire got ripped out from, but I'm not sure. Ideas?????

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Old 10-13-2010, 11:56 AM
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400 wiring

There is only one wire from the H.E.I., unless you have a tach, that would have a wire from the H.E.I. to the Tach., I don't have a Gm. wiring diagram, in fact I have wired many cars, all street rods, but with an after market wiring board, And very few of them if any Use their board like Gm. Even though the are for a Gm. engine. There are so many different ways to get power, from A to B. But what I said is right If you do not have a Tach. then they are getting power for something else. the one wire goes from H.E.I. to Ing. switch. You said they are spliced together so I would Guess They are getting power for something else.


Later 35terraplane
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Old 10-13-2010, 12:43 PM
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I do have an aftermarket tach insidede the car. I'll have to go see what wire is going to it and trace it back.
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Old 10-13-2010, 03:14 PM
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it looks like the green wire I have runs back to the tachometer. The tach has 3 other wires going to it, I dont know where they go. The 2 wires that are crimped together lead back to the little fuse box behind the brake pedal. I think those have to be where the yellow wire came from. I think one of the wires feeding the yellow wire is the purple wire that used to go to the coil. I dont know what the other blk/yel wire is from
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Old 10-13-2010, 04:34 PM
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The heavy yellow wire is the feed for the HEI in most cases
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Old 10-13-2010, 06:37 PM
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Pontiac 400 wireing

Quote:
Originally Posted by adam83
it looks like the green wire I have runs back to the tachometer. The tach has 3 other wires going to it, I dont know where they go. The 2 wires that are crimped together lead back to the little fuse box behind the brake pedal. I think those have to be where the yellow wire came from. I think one of the wires feeding the yellow wire is the purple wire that used to go to the coil. I dont know what the other blk/yel wire is from
Does that box behind the brake pedal have a lever on it? If yes does the brake arm hit that lever when you use the brakes? If yes do you have a third brake light on you car? If you do the black wire with the yellow strip goes to the third brake light I beieve. T-bucket 23 is right on the yellow wire to HEI they are sometimes also orange. Is the box behind the brake pedal a fuse panel or a juction box, The wire going to the HEI should be coming from the IGN side of the ING switch aand without having the diagram in front of me foe the GM column I think that there is a purple wire on the ING switch connector on the column. But those wires do not always go by color.
Column mounted ignition switches MAY identify connections by letter/number sequence rather than color.
Again I know how to wire A lot of boards and using Gm colors But I don't wire by GM diagram. Also the black wire with yellow stripe GM in the older cars does not use one color wire with a stripe often I have seen that color on third brake lights from the brake light switch.
the back of your TACH one wire to HEI, one to the fuse panel, one to the dash panel terminal on your light switch, and I'm not sure on forth, I need some help there. As far as which goes where not a glue. That's why it's a good idea to take some wire tags and write on them where each wire came off from GM didn't use a lot of colors, like someone said on the form they thought they had only four colors in mind.
I don't know if this will help or not, you were asking a lot. we can go one step at a time, but you might have to call or go online with the name of your TACH to find out what goes where. If it is a VDO I have one in the shop I'm sure it will say, if not give us the name, if one of the guys has one he would be able to tell you. Check it out let us know.

Later 35 terraplane


Forth to ground on tach
.

Last edited by 35terraplane; 10-13-2010 at 06:44 PM.
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Old 10-13-2010, 10:26 PM
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Oh yes, I know these wiring questions can be too broad and very hard to answer. But the explanation of what the 2 wires were that lead to the hei really helped, and I was able to figure it out. I crimped a new wire onto the 2 wires (purple and blk/ylw). I read a few diagrams, and it looked like there was one wire going from the fuse box (yes, I meant the fuse box in my earlier post) to the coil. I dont know why this purple wire is crimped with another wire, but I decided to let it be cause the car was like that before I got it, and i dont have time right now to fool around with it. i will do it later. ANyways, I got the new wire to replace the missing yellow, and hooked it all up. The engine fired right up! Now I got some miscellaneous stuff to attend to, the biggest being the god D@mn copper header gaskets....they leak like a pig....absolutely horrible...
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Old 10-13-2010, 10:59 PM
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pomtiac 400 wiring

Great glad I could help a little Good luck with the gaskets. And don't leave a wire hang loose too long, it could be hot and swing into something, and you will have more troubles than you have.


Later 35terraplane
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