greg mgm
1/2 ton status
I'm not a mechanic or a professional distributor technician. What I am is a bit more knowledgeable about distributors than I was 2 weeks ago. 
I'm replacing the distributor in my 78 GMC 454 truck, and together with my love of photography, put this distributor report together. It's only for general knowledge and to see what's inside a "dizzy". Most of you know more about them than I do, but I'm hoping this could help shed some light on the subject. My thread "Diagnosing a Starting Problem" http://coloradok5.com/forums/showthread.php?t=239593 is the reason I'm replacing the distributor.
Removing the distributor is done by unplugging the + wire, and the 3 conductor plug. The plug is indexed so it can't be re-plugged in wrong-
Then remove the 1/2" retaining bolt (mine is 3/8) Twist and lift up....and this is roughly what you have-
Removing the coil cover reveals uh....the coil-
Here's the coil removed from the cap-
Under the coil is the ground terminal. If you forget to put this back in, you can forget about starting the engine-
The bottom of the coil has a round metal section that makes contact with the rotor. This particular coil was in a bag stored under my seat...I mean the trucks seat...Obviously it would need to be cleaned before using it-
Coils can be tested with an ohm meter. The readings between the "Tach" and "Batt" terminals should be less than one ohm. Between the rotor button and "batt" term, and between ground and rotor should both read between 6000 and 30,000 ohms.
Also under the coil is the rotor button and a rubber washer which gets dialectric grease on it-
The cap is indexed and can only be installed with the tab in the slot-
Under the cap we see the rotor and electrical components-
My rotor was in good shape. If yours has corrosion or carbon marks, it's cheap and easy to replace-
Under the rotor, we see the ignition module, capacitor, magnetic pickup assembly and timing advance components. FYI the capacitor is only for radio RFI suppression and does nothing for the ignition-
A closer look at the pickup "pole piece" and assembly-
To remove the shaft assembly, you need a hammer and punch-
Thump out the roll pin-
The gear and washers come right off-
The bottom of the shaftless distributor housing has holes for oiling. The upper bearings (bushings actually) are lubed with grease and should have a frick'in zerk fitting....Well, I wish it had one! You might want to lube the top bushing once in a while. If the shaft or bushings are messed up or scored, then definitely replace them. Here's the bottom of the housing-
With the shaft assembly out here's what ya got-
A Look Inside a Distributor Part 2-
http://coloradok5.com/forums/showthread.php?p=2338931#post2338931
I'm replacing the distributor in my 78 GMC 454 truck, and together with my love of photography, put this distributor report together. It's only for general knowledge and to see what's inside a "dizzy". Most of you know more about them than I do, but I'm hoping this could help shed some light on the subject. My thread "Diagnosing a Starting Problem" http://coloradok5.com/forums/showthread.php?t=239593 is the reason I'm replacing the distributor.
Removing the distributor is done by unplugging the + wire, and the 3 conductor plug. The plug is indexed so it can't be re-plugged in wrong-
Then remove the 1/2" retaining bolt (mine is 3/8) Twist and lift up....and this is roughly what you have-
Removing the coil cover reveals uh....the coil-
Here's the coil removed from the cap-
Under the coil is the ground terminal. If you forget to put this back in, you can forget about starting the engine-
The bottom of the coil has a round metal section that makes contact with the rotor. This particular coil was in a bag stored under my seat...I mean the trucks seat...Obviously it would need to be cleaned before using it-
Coils can be tested with an ohm meter. The readings between the "Tach" and "Batt" terminals should be less than one ohm. Between the rotor button and "batt" term, and between ground and rotor should both read between 6000 and 30,000 ohms.
Also under the coil is the rotor button and a rubber washer which gets dialectric grease on it-
The cap is indexed and can only be installed with the tab in the slot-
Under the cap we see the rotor and electrical components-
My rotor was in good shape. If yours has corrosion or carbon marks, it's cheap and easy to replace-
Under the rotor, we see the ignition module, capacitor, magnetic pickup assembly and timing advance components. FYI the capacitor is only for radio RFI suppression and does nothing for the ignition-
A closer look at the pickup "pole piece" and assembly-
To remove the shaft assembly, you need a hammer and punch-
Thump out the roll pin-
The gear and washers come right off-
The bottom of the shaftless distributor housing has holes for oiling. The upper bearings (bushings actually) are lubed with grease and should have a frick'in zerk fitting....Well, I wish it had one! You might want to lube the top bushing once in a while. If the shaft or bushings are messed up or scored, then definitely replace them. Here's the bottom of the housing-
With the shaft assembly out here's what ya got-
A Look Inside a Distributor Part 2-
http://coloradok5.com/forums/showthread.php?p=2338931#post2338931
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