Syncronizing Twin Distributors ?

[Guest Silverghost]

My 1927 Springfield Rolls~Royce Phntom I has twin DeJon distributors that have a single ignition point set in each distributor on the big six cylinder engine. Twin spark plugs for each cylinder. Twin coils. Twin ignition systems: both points & coil type. Not Magneto !

It's interesting to note that the original DeJon rotor arms have a "L" shaped distributor electrode contact area ! I assume this allows easier ignition advance syncronizing !

You don't have to fire on the center of the rotor electrode this way !

Question: What are the best methods to syncronize each distributor to fire at exactly the same time ?

I have done hundreds of very precise conventional point type "Tune-ups" over the decades ~

But NOT with twin Distributors !

I have several very accurate point dwell meters & timing lights, feeler gauges etc~

Flywheel housing has a port with pointer and degree * markings on the flywheel itself !

Each distributor can be moved seperately and locked into fixed position.

Then spark advance control will then move both distributors in tandem.

There must be a simple method of doing this ?

A friend suggested using a twin-trace oscilloscope to syncronize firing traces~

I do not own one !

But I don't think this is necessary as these scopes did not exist in 1920s !

There must be an "Old School" method to do this accurately?

I have access to an old Sun distributor set-up machine ; but I don't think this would help syncronize twin distributors; just twin dual points which these distributors do not have.

I have used the Sun machine to syncronize dual point distributors in the past~

But these are only single contact point units !

I will check each distributor on the Sun machine to check automatic advance weight & spring curves of each unit as to advance rate at various speeds, total advance etc so they should be the same before replacing them and attempting to syncronize them to fire at exactly the same time.

I have done this on race cars & boats many times before !

Still got my box of advance weight springs !

I have adjusted advance curves on race cars & boats .

Never have I adjusted twin distributors !

By the way~

I am a Mehanical Engineer~

Possibly being too fussey?

Any And ALL Ideas Greatly Appreciated !

Thank's

.

Edited October 3, 2010 by Silverghost (see edit history)

[hchris]

Perhaps you are over thinking this one, normally the fitment of twin ignition systems is a way of achieving more efficient combustion by igniting the mixture on opposing sides of the combustion chamber thus creating a uniform flame front.

I assume you have the ability to rotate both distributors for advance and retard, so why not set one with points just opening then set the other the same, if you finish up with a split of a degree or two I am not sure this will make a significant difference as the engines of this era were typically slow reving and under stressed.

The only other factor that may apply is if the distributors are designed to fire in sequence, a bit like dual point devices which use this technique to increase the dwell time; in which case you will really need the proper specs.

[DavidAU]

A Phantom 1 Handbook should detail exactly how to set the ignition timing. If you haven't got one they appear fairly regularly on ebay or get a copy of one through the RROC

The hand book for my P11 which has both coil and magneto ignition shows exactly how to set it up off the timing marks on the flywheel.

David

[Guest Silverghost]

I have the Phantom I service notes and set distributors as per instructions.

However~

One distributor seems way out of sync from the other.

I had hoped to find a more accurate way of getting them to fire the points at the same time.

It would appear that in the past these distributor units were removed and not replaced accurately .

[DavidAU]

Brad,

If you go to the Rolls Royce Owners Club of Australia technical site it has the timing details for pre-war models including the Phantom 1 and it may be helpfull to you.

Technical Library - RROCA-info

David

[Guest cben09]

Simple//from old fodge,,,Set 1 where you want it,,,while rinning set the other,,Turning retard it will change the engine speed until it passes the point of #1 firing,,further retard and the #1will be in charge,,,advancing will change nothing UNTIL it goes past the ign point of the other distrubitor,,,WHEN its all in sync,,test by the IGN switch,,left/right/both,,Shifting from L to R should not affect the speed,,,,Both may be a bit cleaner running,,Please pass this on to your stable boy and chauffeur,,as they may one day need to do this on the road,,Cheers Ben

[edinmass]

It's rather easy to get them to fire at the same time. Set up each on the sun machine as you would do normally. Then use two test lights to set the second distributor to fire at the same time as the first. Remember that unless they have the exact same advance curve the timing will only be exact at or near idle. The lights will indicate when the are opening and closing at the same time as they should both blink on and off simultaneously. Just use the hand crank to turn the engine. It would be easier with two people. I would use TDC and set the first to open, and then set up the second. Let me know if what I said makes sense. Ed

[Guest Silverghost]

Guys:

Thank's for all the tech tips !

I have both distributors off-engine now and have set the mechanical advance curves of each on the old SUN Distributor machine.

My two advance curves are exactly alike now at all speeds ...

At least~

As much as is humanly possible given the old spring/weight systems used at the time !

They were very different at first & way out of spec !

This explains why each fired at different crankshaft posiion timing...

I will now use two 6 Volt test lights , one on each distributor, and set-up both the same with the old hand crank method explained above .

Hopefully they will both then be syncronized ! ?

I will keep you all updated at to my final results !

Thank's for your help !

Edited October 18, 2010 by Silverghost (see edit history)

[tom_in_nh]

Your final result?.....