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Distributer shaft endplay.

y5mgisi

y5mgisi

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On my caddy 500 motor i think i have too much end play in my distributer shaft. I have not put a dial indicator on it yet but i would venture a guess of around .180" of endlpay. How much is too much? Can i take out the slop by adding shims between the drive gear and the housing? Also where can i find some shims if i can do that?
 
Id check the side play as well while at it,if the bushings are shot and running points the dwell will be all over the place and if HEI the air gap will be hugely varying. Might be able to still buy a bushing or rebuild kit or a rebuilt dist itself. Regarding the slop up and down,try a spring washer that dosent drag but takes up the play. Should be avaliable from any good hardware or AP store.
 
I used a hardened washer

If I remember correctly I shimmed it at around .010
 
+1 more. For HEI try to get to .010.
http://www.rustpuppy.org/ignition2/Ignition%202b.htm
Moroso, Mr. Gasket, etc make decent shim kits. Of note, if you do take the clearances down to this level make absolutely sure that the distributor is bottoming out on the oil pump. If it is, you will need shims between the manifold and distributor as well. I've performed the same procedure and it worked well in my application.
 
WOW so in that link it says that .064" of end play will make for up to 5* of timing variation. I suppose that could mean that mine (which is easly more then twice that amount of slop) could have as much as 10*-15* of timing variation. Hmmm, i wonder if that could explain my rough idle situation...
 
I doubt it. Load at idle is constant, I'd imagine any "deflection" of the timing would happen immediately on startup, and stay constant until the load changed.
 
I just imagine it bouncing up and down in the housing. I know it does move alot because the under side of the cap where the coil button pokes threw is all ways really beaten up.
 
The gears are angled, so the force on the shaft is going to be in a constant "direction" as long as RPM is fairly constant. I don't know whether the gears angle would force them to deflect up or down (same deal as a pinion in a rear end) but it will simply move to it's physical limit and stay there, until the load varies, which is where you'd expect to see variation.
 
Right. I do know that it does move up significantly, enough to tear up that coil button area where the rotor receives spark from the coil cause its been beaten up pretty badly in just a thousand or so miles. So i don't know if it just gets shoved up there at start up and stays there or if it just makes contact occasionally but it clearly does travel up too far.

What i envision in my own mind is the shaft getting thrust upward an then the contact at the center of the rotor (which is like a diving board for lack of a better term) Trying to spring it back down ward making it a battle over which force wins. The upward thrust or the rotor trying to shove itself back down. There is no question that a significant amount of movement is going on and that it is a problem that needs to be corrected.
 
The distributor shaft is pulled downward with normal engine rotation because of the helical cut gear. Yes there is "some" movement possible when no load or when shifting (manual trans). I like to shim the gear so there is between .005"-.010" clearance between the gear and distributor housing.
 
I seem to recall the Moroso(Think that was the brand) HEI shim kit I had give the .010" number.
 
Ya im going to go with the Mr. Gasket one i think. And i can assure you that there is a great deal of movement going on. Otherwise why would the under side of my cap be so beat up?
 
y5mgisi said:
Ya im going to go with the Mr. Gasket one i think. And i can assure you that there is a great deal of movement going on. Otherwise why would the under side of my cap be so beat up?
Click to expand...

Too much resistance from either bad plugs or wires can damage the center electrode of the distributor cap. Too much resistance can also burn a hole in the metal tab of the rotor.
 
Also did you check the mechanical advance mechanism for smooth operation. That means a smooth arc and no up and down movement, that will bounce the rotor off the bottom of the cap.
 
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