Yesterday I decided to install new springs on the weights and took everything apart for some cleaning and lubrication. My question is : is it possible to incorrectly assemble (reverse) the weights on the distributor ? I tried to reverse install them but can’t. Both weights appear identical but when they are centrifugally out (statically simulated) one side has some play while the other is firmly against the travel stop (either weight).
Also , does it matter which spring goes on which weight ? I don’t believe so.
I attached some photos of how it is currently assembled and in simulated advanced and not advanced positions. The third photo shows the weights in the fully advanced position and the top (left) weight can be moved about an 1/8".
If the weights are the same weight then they will have the same effect, no matter which way round you fit them.
The principle is that the two springs are different, so that the lighter spring pulls first and the advance rapidly increases from a standing start. Then with further increase in rpm, the second heavier spring comes into play and the advance continues increasing, but at a much slower rate.
Thank you Marek, all reassembled and working fine. I understand the concept of the weights and springs but wondered if I could have made a mistake /reverse the reassembly.
And a thank to Mr. Maury who made me “decide” to change the springs after which the idling was silky smooth…
I have seen the weights put in backwards on a XK150. The car would not rev up. Seems the timing was retarding as the revs increased. Easy to verify with a timing light. It does not matter which post the springs are put onto as they are the same distance ( or should be). Glad it worked out for you.
I have just fitted a 123Ignitions Bluetooth distributor to a '65 E-type of a friend and I am hugely impressed by it. Both Centrifugal and vacuum advance is fully programmable with seperate curves for each (via an app on your phone which communicates with the dissy via Bluetooth). It has a built-in rev limiter, immobiliser and you can also program the RPMs at which the vacuum advance is applied (which I set to 800). The HT wires were only just long enough, and the acorn fittings had to be converted to modern plug-in types.
The engine starts on the first turn of the starter, the engine still runs and pulls smooth well below idle rpm and the engine feels “light” and “effortless” on light throttle.
For a beginning, I programmed the centrifugal curve to offer 15degs advance at 800 rising linearly to 30deg at 2000rpm.
The owner of the car was raving about the car “This car has never gone as well as it does now!!!”.
I looked at the Coil- signal with my Picoscope and could see that the dissy applies a constant dwell of about 2.6ms. The coil on this car was a Lucas unit with a 1.4Ohm coil primary resistance. Screen capture below.
I was interested to read this. Is renewing the springs generally a good idea after high age/mileage? My 57,000 mile 1972 4.2 was converted to breakerless ignition some time ago to dispense with points and condenser - but still has a lumpy idle.
I don’t know if the weights are required with the upgrade but I’m old school and with points and condenser and weights the springs weaken overtime. There are two springs and, like Marek explained earlier, the lighter ones control advance at lower rpm and the heavier one at higher rpms. If the lighter ones are weak or stretched they allow the weight to move during idle causing the advance to move which causes a rough idle. My old springs looked and felt like the new ones but changing them made a difference (see photo of the old ones).
Marco
Conversion to breakerless ignition has no impact on the mechanical action relating to the centrifugal weights and springs that act on them. This means that timing could still be erratic if those weights and springs are not sitting at a constant point (thus with constant advance) while idling.
Should be easy to verify with a timing light. The timing mark should be sitting dead still in one location while idling. If not, it means that the centrifugal system is randomly advancing and retarding while idling.
There is also the possibility that the dissy shaft is worn and thus woble around inside the dissy creating longer and shorter periods between sparks which would also cause erratic spark timing. More reason for a nice new intelligent dissy…
Some interesting discussion here. Paul, at Medatronics 5 speed, says that with the 120 degree firing gap of a 6 cylinder (a plug fires every 120 degrees crank rotation) there is an increase and decrease in engine speed caused by going from compression which slows the engine down, to power stroke which speeds the engine up. This is not noticeable to us but the engine components notice it. This is why he does not recommend the use of a lightweight (aluminum ) flywheel. The transmission will rattle, and the purchaser will blame Medatronics. I suspect that this would have some effect on the weights in the distributor and cause some of the jumping around you see. I’ve never been able to actually get my ignition absolutely stable with a stock distributor. (EDIS - yes). You will notice that advancing the distributor to 20 degrees before tdc at idle will give you a smoother, and faster idle. You can program the EDIS (Megajolt) system to give you zero degrees at cranking speed, and then 18 degrees at idle. At 500 rpm the setting may be at 20 degrees falling to 15 degrees for example at 1000 rpm. This will control your idle speed, and give you a better idle, but not introduce excessive advance to the point of detonation in the lower rpm range. Don’t know if you can do this with a 123.
Thanks. My timing mark is a blur - always has been - and I set it to as near the middle of the blur as I can. Probably time to overhaul the distributor. If that fails, I am tempted by the 1-2-3. system - I hear good feedback about it.
