Need some dizzy help. L16 dizzy on a L20b?

[SaltyMuffinMaker]

Help before I go crazy!!! After a few months of searching I found a distributor off a 1976 L16. I have a 1975 with a L20B and I cant seem to get spark from the dizzy. Ive tried searching and after a night I think ive confused myself even more. What kind of dizzy really is this and is there a way to make it work on a L20b? Thank you!

 

My L20B dizzy is on the right.

[datzenmike]

The one on the left looks like it was converted to a PerTronix? Maybe an optical trigger? Not stock for sure. You won't get a spark from it without an igniter modile or HEI unit from a GM.

[SaltyMuffinMaker]

Mahalos Mike! So would a 1977 Camaro HEI work with that dizzy? It has 3 plugs instead of just the one that I have had. I read somewhere on here that would be what i'd need if it was pertronix(I really had no idea what was what before).

 

Or would it be better to just find another dizzy with points?

[DanielC]

First some basic ignition theory.

When you turn on the ignition, battery power is applied to the coil. Sometimes there is a resistor that cuts back the battery voltage a little, but power is applied to the coil positive.

There is a switch controlled by the engine, that grounds the coil, and most importantly, switches off the coil when a spark is wanted.

 

That is the same for a old car, with points, for a matchbox distributor, for a more modern car with coil packs, or even the latest cars with coil on plug ignition systems.

 

The l-20 distributor you have is an optical sensor type of distributor. It needs a "black box" that actually switches the coil on and off.

A matchbox distributor does the same thing, except the "black box" is mounted on the side of the distributor.

 

A points distributor does not need the "black box", It switches the points directly. However, the points have to close sometime before a spark is wanted, and then open exactly when it is time for the spark. When the points close, the coil makes a magnetic field inside itself. But this takes a little time. If the points do not stay closed long enough, the magnetic field will not get strong enough.

The points must be clean, or even if they are closed, they do not make electrical contact, and the system will not work.

 

The time the points are closed is controlled by the point gap. About 17 thousands of a inch is pretty close. but the feeler gauge cannot have any oil on it, or it will get the points dirty. There is also a thing called a condenser wired across the points. It absorbs alittle electrical energy when the points just start to open, so the points do not spark, or arc. if the points spark, the spark plug does not.

If the condenser is bad, the spark will not happen.

 

A quick way to check a points system is to measure the voltage at the coil minus terminal. Before the points open, it should be zero, because that terminal should be connected to ground by the points. When the points open, there should be voltage at that terminal.

 

For the optical trigger to work, you need the "black box" that matches the optical distributor.

[banzai510(hainz)]

All L series dizzys will work with the matching pedastal.

 

I cant see our dizzy on here but soemthing will work for ya. Its a simple system.

 

middle of the pacifc? Like ? Hawaii? Guam? Johnson island?

[SaltyMuffinMaker]

Thanks Daniel and banzai. I'm on Hawai'i and I tried mounting the L16 distrbutor on my L20b. I take it the pedestal is the piece below the main part of the distributor? I think a screw is holding em on. The L16 fits on top, but I noticed both looked different and the L16 had a 3 plug.

 

So the best way to check the points is to put a volt gauge(I only have a test light) on the - of the coil...and then try crank it and if it gets a reading, it's good? i'll search how to clean points and get back to you guys asap. The trucks not where I live.

 

what would be better to run? A stock points system or the other one I have? The L16 is a optical trigger one?

[ggzilla]

Run the L16 one. Just get new point and condenser and set with a feeler gauge.

[DanielC]

I agree with ggzilla on this one.

[banzai510(hainz)]

try running the point one

 

[SaltyMuffinMaker]

I went and asked for a new point and condensor for a L16 distributor and they looked at me like I was stupid. I really think my stock L20 dizzy condenser is bad but im not totally sure and ended up buying an used L16 with a dual spark. Quick trip to Napa got me a new rotor and I went to put the dizzy in and realized i'll need to change the mounting plate. I looked at it some more and realized i'll have to do the timing since im confusing myself on firing order(should be same, right?), vacuum advance and setting everything up aka doing timing correct...so here I am on ratsun about to look up the timing.

 

The L16 dizzy cap goes on one way, the mark on the cap is number one cylinder...and then it's 3-4-2 going counter clockwise?

That mounting plate looks like they flipped it upsidendown. i can put in 

Vacuum advance, need it or dont need it? The positions changed for it and people have told me it does fine without. is it one of those if it works, leave it kinda things?

[banzai510(hainz)]

if you mis match the timming plate and pedastal from a l20 to a L16 it wount line up.

 

L20 condensor is inside. simple Roack auto should have photos. print a copy and show them.

 

L16 had single point and dual point dizzys. the timming plate and pedastal are the same.

The main points on adsusl point will have the bigger condensore.

 

 

to me the L20 single point is a ezer set up. if you got thr matching pedsstal setup/

 

on my vid the motor is alwas set up or referenced to TDC