broken ignition rotor, why?

[haycait911]

kind of hopped on it in first and it revved up pretty quick. then died. noticed dist cap was unclipped, fixed and tried again. much popping and banging but no joy. took off the cap and saw the rotor was sitting funny. seems the rotor hit the inside of the cap, breaking off the locator tab on the inside of the rotor. stuck it back on in the right spot and went home at low(er) rpm's.

what caused this? my thought is worn dist bushings allowed too much movement when revved quickly and allowed rotor/cap contact. the dist shaft has slight side to side play and quite a bit of up and down play. how much play is to be expected?

any input much appreciated, Don.

( jeeez, I really gotta see a manicurist one of these days! )

[Steve@Rennsport]

You didn't have the rotor seated all the way down when it was installed.

[Mysterytrain]

Don,
Trust me on this. The bushings are shot in your distributor. I had the exact same experience a few years ago. I didn't realize what was happening and continued to drive the car. The distributor seized and sheared off the drive gear. The distributor drive gear dropped into the case and was shoved out the side of the case by the intermediate shaft gear. Forced a rebuild. Fix that distributor, fast!

[haycait911]

by feel, there's probably 1/32" play side to side, and maybe 1/16" ( or a bit more) movement up and down in the shaft. that can't be good, can it?

[911pcars]

Originally Posted by Steve@Rennsport

You didn't have the rotor seated all the way down when it was installed.

+1. I concur.

Sherwood

[Gunter]

Originally Posted by haycait911

by feel, there's probably 1/32" play side to side, and maybe 1/16" ( or a bit more) movement up and down in the shaft. that can't be good, can it?

Like Steve says: most likely the nose wasn't in the notch.

The axial play is not as important as the radial play.
1/32" radial play is about 0.8 mm; that's too much.

[JFairman]

Seems like way too much up and down play.
Maybe a thicker shim washer between the gear and the housing would help that if it has the same clearence at that end.

Take a machinest scribe and pull the felt pad out and see if everything is tight in there.

It would be a good idea to take it apart and see if you can take up the slop.

[haycait911]

thanks guys. I have a spare dist that has much less play. I guess I'll stick it in anyway. I haven't had a problem in 5 years, until now. so maybe the rotor wasn't seated. seems like a no-brainer to put in the spare dist though, better safe than sorry.

all input much appreciated, you guys always come through. Don.

[Wayne 962]

Sounds like a safe bet to have the distributor bushings looked at...

-Wayne

[haycait911]

note: upon further inspection, the rotor is hard against the pertronix trigger wheel when installed. perhaps it's not completely seated? I'll shave a little off the bottom of the rotor to gain clearance between it and the trigger wheel. then I know the rotor will be completely seated.

[RoninLB]

Originally Posted by haycait911

rotor is hard against the pertronix trigger wheel when installed.

perhaps it's not completely seated?

I'll shave a little off the bottom of the rotor to gain clearance between it and the trigger wheel. then I know the rotor will be completely seated.

I had same problem with stock rev limit rotor & Pertronix.

for some mystical reason the VW pelican# Bos-04038 always fits ok..

The screw attachments aren't the greatest either. I use blue loctite.

[porsche930dude]

My guess is that the cap came uncliped and because it wasnt seated right the rotor snagged on it and thats how it broke

[stlrj]

And this has never happened before you installed the Pertronix? So you can forget worn distributor bushings.

I'm for re-checking the trigger wheel installation which is preventing your rotor from seating fully. Get a hold of a caliper to see how deep the inside of your rotor is and compare that to how far down the trigger wheel needs to go.

No caliper? OK then, try a toothpick.

When you're done with this, you could have your nails done here:
http://www.youtube.com/watch?v=SsWrY77o77o



Cheers,

Joe

[Howard M]

I remember how hard it was to push my Pertronix trigger wheel home all the way. Maybe a (very) firm push will get you the added clearance you need.

[Rrrockhound]

I'm resurrecting this old thread because I have this problem. I've eaten up two rotors in about 20 miles, and I know when I installed the replacement rotor I pressed it all the way home, so I'm thinking excessive distributor play is chewing up my rotors. I'm guessing there's about 1/8 inch up and down play, but it's hard to tell because everything's still too hot to really work on. Any ideas short of paying $1100 for a rebuilt dizzy?

[c0metdot]

is the cap uninvolved?

An option:

Rebuilt Bosch 383 / VJ4BR25 / 010 / VJ4BR8 / 019 / VJR4BR18 / 022 / VJU4BR8 / "Big Cap" 40hp Distributors