Cap and rotor alignment,

Hello, I have been fighting a ignition problem in my car all last summer and I want to check the rotor to cap alignment to see were things are when it sends spark to the wires. Can I just take a old cap and drill a hole in the top to see inside while it is running with a timing light to check this? Seems like the problem showed up after shortening the the advance slot in the mechanical advance. I am wondering if I shortened the wrong end of the slot? It is a buick dist with a stinger S-4 kit in it. Tom W

 

Someone should make a clear plastic "test" cap for this purpose.:bglasses:

 

I have a clear cap but I am unclear that you would see anything useful.

 

I think what he means is the rotor is out of phase with the wire towers............ If they are too far apart during firing, you would see a long arc between the tip of the rotor and the point where the end of the contact goes through the cap for the plug wires.:bglasses:

 

Hi, Yes that is what I am trying to see, where the rotor is aimed when it sparks, I am wondering if it is far enough off that it sometimes jumps to the wrong plug wire or not at all. Tom W

 

I think what you may be looking for is someone that can put the car on a "scope" See what all 8 firing lines look like... Having a clear plastic cap (Mr. Gasket makes em') is gonna tell you just about ZERO!.... If the rotor is too far from the "post" wouldn't that be just advanced timing or horribly retarded timing??? Do you have an high speed eye calibrated to see at least 800 RPM and the difference between a few degrees???

Seriously, find someone with an old time type o-scope or one of the newer analyzers with a digital KV / O-scope type display.

regards and good luck

 

You can see it if you use a timing light.:bglasses:

 

I don't see how it will change timing, all I want to see is after the full advance comes in is where the tip of the rotor is compared to where the plug wire terminals are in the cap, I would think the rotor tip should very close to the wire trerminal it is sending juice to, not a 1/4" passed it or 1/4" before it. I don't know how to explain it any better. Sorry for the confusion on this. Tom W

 

You can either drill holes in the cap, or get a clear cap, wither way you use a timing light th "freeze" the rotor while that plug fires, allowing you to see where the rotor tip is in relation to the cap.

Run the engine up through the rev range, and you'll see where the two points go relative to each other.

 

Iwill have to check that out when it gets warmer here. But with my luck it is the ignition box that is going bad. TomW

 

Here's the next question:

I've read about all of the above, and seen it done, but the follow-on question is:

If the rotor is out of phase with the cap terminals, how do you fix it? The distributor plate is fixed, the rotor is fixed, and the cap indexes to one spot. Arruuuh?