What order do the wires go on the 500ci distributor cap?

airbrushguy

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1976 eldorado
About to install wires on the engine that I bought that had no wires on the distributor cap, does anyone have a
diagram of their placement?
Thanks
 

5one9

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You’ll probably need to find TDC on the firing stroke of #1 and see where the rotor is pointing.
 

PSYKO_Inc

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Exactly what 5one9 said. Line up the timing mark on the crank and see where the rotor is pointing, this will give you a 50/50 chance at getting it right. If you want to be 100% sure on the first shot, you can pop the pass side valve cover off and make sure both valves are closed on #1. Keep in mind that the cylinders are numbered differently on these engines than other GM platforms; pass side is 1357 and driver side is 2468. Firing order is also different than other GM engines, should be 15634278, with the rotor turning clockwise.
 

48Austin

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18436572. Just kidding. Cad is dfiferent.
 

airbrush guy

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Ok, so firing order is 15634278
Which post on the distributor is the number one wire on and what is the direction of rotation from there?
Thanks
 

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PSYKO_Inc

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It depends on where the distributor is indexed in relation to the cam. (This is why the timing marks are on the crank and not at the distributor.) You need to turn the crank until #1 is at TDC of the compression stroke, then see which terminal the rotor is pointing at. Rotation will be clockwise.
 

Caddylackn

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Ok, so firing order is 15634278
Which post on the distributor is the number one wire on and what is the direction of rotation from there?
Thanks
Pull the spark plug from the #1 cylinder and have somebody stick their thumb over the #1 spark plug hole as you turn the motor over so the timing pointer approaches 0 TDC. If their is air pressure on their thumb when getting close to the TDC mark, then you are at true 0 deg. TDC. Once you are at 0 TDC, now pull the cap and look where the rotor is pointing to, this is #1 cylinder. I always put a piece of masking tape with #1 on the cap, then mark the rest of them on the cap per the 15634278 firing order. I also write the firing order somewhere in the engine bay, for future reference.

If your friend doesn't have air pressure on their thumb when approaching 0 TDC, turn the motor over a full 360 degrees and then you should be at 0 TDC.
 

airbrushguy

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Thanks fellas, very helpful.
I'm cutting new expensive wire and didn't want to screw up the individual lengths. I know the distributor is still in its stock position, so I figured the #1 plug wire is probably
in the stock position. Thanks to Covid, I'm working by myself so I'll have to become a contortionist and turn crank with finger on hole by myself.Would be a little easier if the engine had a bolt in the center of the crank pulley.
Guess I'll have to use a strap wrench around the pulley.
Thanks
 

5one9

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loosen up the number 1 spark plug until it is only engaged about two turns. turn the crank clockwise. you'll hear the air seeping past the plug threads on the compression stroke. once you hear that seeping noise, then bring the timing mark to zero on the tab. wherever the rotor is pointing is number 1 on the cap.
 

5one9

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they actually make a screw in spark plug looking whistle that is supposed to work well
 

48Austin

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Thanks fellas, very helpful.
I'm cutting new expensive wire and didn't want to screw up the individual lengths. I know the distributor is still in its stock position, so I figured the #1 plug wire is probably
in the stock position. Thanks to Covid, I'm working by myself so I'll have to become a contortionist and turn crank with finger on hole by myself.Would be a little easier if the engine had a bolt in the center of the crank pulley.
Guess I'll have to use a strap wrench around the pulley.
Thanks
Don't remember. But I think a sbc goes in the hole> It is threaded. Fine thread.
 

5one9

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9/16" fine thread with a 13/16" head. It can be as long as 1-1/2". You'll need to chase the threads as they are typically full of dirt.
 

PSYKO_Inc

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You can also turn the crank by using a wrench on the power steering pump nut. If the belt slips you can pull the spark plugs out to release the compression and make it easier to turn. Leave the #1 plug in and you should be able to feel when that cylinder is on its compression stroke.
 

Caddylackn

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The 9/16" fine is also the same thread as a wheel stud for a 3/4 or one ton pickup. You can pick one up at any auto parts store, then weld a large nut on the end and you have a method of easily turning the motor.
 
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