distributor rotor spins by hand

[mrnda]

1974 K20 pickup  350  automatic transmission  4wd

bought truck running rough, timing issue. 
driving it home it died, while checking engine noticed distributor loose (hand loose)
got it home, adjusted timing and had it running went to tighten distributor and suspected the cap was not secured all the way around.  The previous owner was messing with the idle when we bought it.  Tugged on the cap and it came half way off, engine died.  Will not start back up.

while checking things out, I had the distributor cap off and noticed the rotor will spin by hand?? it has an accel distributor on it top looks exactly like the pic that hopefully is posting with this.  My assumption is this is the design?  hopefully all I have to do is get engine to tdc, move the rotor to the #1 position and it will fire up.  Before I proceed I wanted to consult the board of wisdom here.

Thanks and sorry for the long read.

[enaberif]

The rotor should not spin by hand since the distributor is meshed together with a gear at the bottom.

If the rotor CAN spin by hand it sounds like your distributor is not completely seated and you can confirm this by ensuring the distributor is fully seated against the intake manifold.

https://www.youtube.com/watch?v=O4WRL513Gx4

[mrnda]

thanks for the quick response, ill hit it when I get home.  Much appreciated.

[Irish_Alley]

could be the gear at the bottom of the distributor shaft if the distributor is bolted down.

[mrnda]

Thanks Irish, I will look into that as well.

[Engineer]

When you say "spin", how much?

There is a centrifugal advance just under the rotor. You should be able to turn the rotor about 15° but it should snap back when you release it.

[mrnda]

it can spin all the way around, there is tension on it the whole time and at one point there seems to be a relief with less tension.  Took the distributor out and the gear at the bottom is fixed in place.  The rotor can be turned without anything else spinning, the gear does not move.  I held the gear at the bottom and was still able to turn the rotor.

[Irish_Alley]

try pulling up on the rotor and see what happens

[mrnda]

RUNNING--
with the distributor out, firmly griping the lower gear and turning the rotor I could feel a point where there was a relief in the tension I figured that is where it is suppose to be sitting at, in that point of relief.  reinstalled the distributor and set everything for what seemed to be TDC and it fired right up.

When I was initially working on the timing and noticed the distributor cap loose I must have thrown the rotor out of place when I tilted the cap back to see if the cap was not fully fastened down, which it obviously was not. 

Thanks to everyone for the advice and quick responses it did help a lot.

[bd]

@ mrnda

The rotor is "fixed" to the end of the distributor shaft and should not spin when the gear is held stationary!  The rotor will rotate a few degrees clockwise if the distributor has centrifugal advance, but will snap back to its original position when released.  You expressed that you are using an Accel distributor...

• An HEI style rotor is retained to the distributor shaft with two screws.  If this is the style of distributor that you have then the roll pin that retains the gear has sheared, or there's a problem with the assembly of the advance mechanism to the top of the shaft beneath the rotor.  In either case there maybe enough residual friction to hold the rotor from spinning freely, but the problem remains and the rotor will drift.
  
  
• On the other hand, if the rotor simply presses onto the shaft and there are no screws to retain it, then the rotor isn't properly seated onto the shaft.  With this style of rotor attachment there is an indexing slot in the top of the shaft that must align with a drive key cast into the base of the rotor.
  

Remove the distributor cap and snap a pic of the rotor as it is currently installed and post it.

[mrnda]

sorry for the delay.  Here are pics for the distributor removed from the engine.  really at a loss as far as what the next step should be.  thanks again everyone.

[bd]

Grab the top of the distributor shaft with the attached advance mechanism in one hand and the distributor gear in the other hand.  Twist the gear while firmly holding the shaft and pull the two apart.  If the gear spins or pulls loose, either the the gear roll pin is sheared/missing or the distributor shaft is broken.

[mrnda]

alright, it will spin but does not seem like it wants to separate.  what can be done to fix it or would we be better off just buying another one.

[Irish_Alley]

what spins? the top part of the rotor or the whole shaft

[bd]

Use a pin punch and drive the gear roll pin out of the gear then remove the gear and thrust washer and slide the distributor shaft out the top of the housing.  Clamp the flats at the bottom of the shaft (the oil pump drive key) in a vise.  Grab the top of the shaft with the advance mechanism and try to twist it.  Does it rotate around the shaft?