It's all in the title of the thread...can anyone enlighten me please?

Nothing

Answer is in the title

Chris

To be a little more specific, for both 500F/R/L & 126 -

Static advance = 10deg BTDC
Maximum (centrifugal) advance = 18deg BTDC
Gap 0.47 to 0.53mm
Dwell angle = 78deg +/- 3deg
Rotation clockwise

The only difference is in the condenser -

Condenser 0.20mF (500F/R/L) or 0.25mF (126)

They are interchangeable. Not sure whether the 500N/D is different though.

Chris

Thanks Chris; does that mean that physically they are the same, right down to the teeth on the drive sprocket?

My car has a 126 distributor fitted Peter the teeth are the same. The only difference I beleive is that the 126 is a single unit and the 500 one you can split into 2 parts.

Tony

Vitesse said:

My car has a 126 distributor fitted Peter the teeth are the same. The only difference I beleive is that the 126 is a single unit and the 500 one you can split into 2 parts.

Tony

Click to expand...

Ah Ha! Thanks Tony. Just what I needed to know.

Early on in my adventures with the mighty two-pot screamers, I interchanged a later model 126 distributor with the worn out one in my 500.
They are physically, electrically and mechanically the same though I'm not sure if the internals are interchangeable. I think you need a spacer with the 126 distributor.
I now run an electronic distributor.
Might dig out the old ones today and have another look just to make sure.
Chris

I found a couple of old distributors - one from a late model 500F and the other a rotorless model from a 126.

Both have a gear interface with the cam drive but the 500 one is in two parts as Tony noted. The lower part is positioned and locked into place whilst the upper part interlocks using an eccentric dog. This makes it easier to remove and service the distributor as you don't interfere with the static timing.

The 126 distributor is longer and you will need a spacer (~10mm) in order to fit it to a 500 engine. It is locked using a clamp that is attached to the same post that is used to fix the lower part of the 500 distributor. If you are changing over, make sure you have this clamp.

The insulated mount for the points is a slot cut in the side of the 126 dizzy. It is a drilled hole in the 500 one.

The advance springs are the same for both but the weight mount system is different. This shouldn't bother you. The 126 shaft is longer.

The points base plates are identical as are the points themselves. Condensers have different capacitances but the same physical dimensions and mount the same way.

I don't have a 126 distributor with a rotor to compare but I would imagine that things would mot differ too much.

So, all you really need is the spacer and clamp and the two are interchangeable.

From memory, the rotor turns 90 degrees clockwise when you are engaging the 126 dizzy with the cam drive.

Photos from the mornings work attached - 500 dizzy on left or below.

Chris

It's really odd Chris as my 500F has always run a 126 distributor but when I changed it for a 123 distributor I noticed the difference in length and as the manufacturers of the 123 point out you need the spacer for a 500 if I remember correctly.

That said my 500 ran perfectly well for 20 odd years without the spacer? All I can imagine is that there was enough gear available to mesh together but that said they are probably worn badly from that?

Tony

Hi Tony,

I've attached a photo of the underside of my engine with the sump removed.
You can see the helical drive on the camshaft that engages the gear on the distributor shaft (arrowed).
I don't have a photo of the distributor fitted to the engine so I don't know how much of the gear faces are normally meshed.
Maybe the early 126 distributors were shorter - I don't have one so I don't know.

I guess that if you are thinking of changing, compare the lengths before fitting.
Spacers, if required, are available.

Chris

Great stuff that; thanks guys
I think, on balance, for a spare I would go for a proper 500 one or have mine professionally refurbished when the time comes. Although clearly, the 126 one can be used, it is actually quite different; so thanks for taking the time to illustrate that.

Adding to the conversation here. I’ve been wrestling with intermittent problems for a while - recently it has seemed to be “blown” condenser. Car warms up, I accelerate hard to change up to 3rd or 4th and the car suddenly loses power and dies. Replace condenser and car runs rough, once cylinder or backfires.

Today I took the distributor off and see I have a 126 distr without spacer on my 499cc 110f 500.

Could the crankshaft gear creating its own grooves (https://ibb.co/4ZpRY07 )at the top of the pinion piece be stopping the tiny amount of meshing on the actual pinion, so when the engine gets hot and spins at high revs causes the timing to slip and problems to ensue ???

I have a spacer on order to see if it helps my problem. If so, what a great start to 2021!!

irvb said:

Could the crankshaft gear creating its own grooves (https://ibb.co/4ZpRY07 )at the top of the pinion piece be stopping the tiny amount of meshing on the actual pinion, so when the engine gets hot and spins at high revs causes the timing to slip and problems to ensue ???

Click to expand...

When I first looked at the picture I thought they looked machine but I checked my 126 distributor that ran in a 500 without a spacer and it does indeed have similar grooves but not as pronounced. But having said that if you look carefully at the picture above where the 500 and 126 distributors are compared side by side you can see similar marks on the 126 one, so I suspect they are indeed part of the machining process. Which unfortunately doesn’t help you in finding your problem. Obviously the spacer is required but I ran my 500 for 20 odd years with no issues without one?

Just to add when I look at the gear on the end of the distributor shaft. I can see wear on the teeth about halfway across all of them where they partly were meshing with the drive on the camshaft. If I recall I don’t think the spacer that comes with the 123 is as big as 10mm it is more like 5-6mm?

irvb said:

Adding to the conversation here. I’ve been wrestling with intermittent problems for a while - recently it has seemed to be “blown” condenser. Car warms up, I accelerate hard to change up to 3rd or 4th and the car suddenly loses power and dies. Replace condenser and car runs rough, once cylinder or backfires.

Today I took the distributor off and see I have a 126 distr without spacer on my 499cc 110f 500.

Could the crankshaft gear creating its own grooves (https://ibb.co/4ZpRY07 )at the top of the pinion piece be stopping the tiny amount of meshing on the actual pinion, so when the engine gets hot and spins at high revs causes the timing to slip and problems to ensue ???

I have a spacer on order to see if it helps my problem. If so, what a great start to 2021!!

Click to expand...

Not related to distributor differences but fault could be Possible faulty ignition coil or rotor arm insulation failing when warm . If you have spare rotor arm try that first as it's nice and easy to try.
Cheers
Jack

Vitesse said:

When I first looked at the picture I thought they looked machine but I checked my 126 distributor that ran in a 500 without a spacer and it does indeed have similar grooves but not as pronounced. But having said that if you look carefully at the picture above where the 500 and 126 distributors are compared side by side you can see similar marks on the 126 one, so I suspect they are indeed part of the machining process. Which unfortunately doesn’t help you in finding your problem. Obviously the spacer is required but I ran my 500 for 20 odd years with no issues without one?

Just to add when I look at the gear on the end of the distributor shaft. I can see wear on the teeth about halfway across all of them where they partly were meshing with the drive on the camshaft. If I recall I don’t think the spacer that comes with the 123 is as big as 10mm it is more like 5-6mm?

Click to expand...

Thanks - and to Jackwhoo - I’m really clutching at straws, have been round the houses of every other part of the ignition system I think. I’ll report back when I make progress!

If you are continually suffering condenser problems, try fitting one of the "Swftune" competition condensers. They are not cheap but as well as being very well made (designed for competition cars where the rules state that they have to retain their original ignition system---from minis to GT40s) they do not have to be mounted on the distributor. They can be mounted up by the coil where they are not subject to the hot air being blown over the distributor (and them).

Swiftune condenser arrived today, and waiting for a spacer for the distributor. I'll get this little car running reliably if it kills me!