308 distributor advance

Can someone tell me about the springs and weights in my 308 distributor. I stripped it to lubricate everything (it's all in good shape as far as condition is concerned) but the springs / pins look unusual and I want to check that they're right before proceeding. There are 4 springs in total these seem to be part nos. 0120F although no internal parts seem to be listed on the ferrari UK site.......... There are 2 short springs (in the short bores) which only come into play at higher rpm....... and 2 longer springs in the deeper bores. Should these 2 springs be the same or different and what spec should they be?

In the photos you can see the distributor internals. It's a 1978 Euro model with Marelli 200 series exectronic ignition. Note the difference between the 2 longer springs and see the difference this makes on each side of the advance mechanism........ of the 2 longer springs, the shorter one with the larger wire diameter seems to do very little - it only comes into play well after the 2 short springs and effective seems to act as a stop for maximum advance - is this really how it is supposed to be - it does very little else. I have arrowed the longer springs installed in the distributor at rest (no advance) see how there is a gap between the pin and the housing on one side - this doesn't look right. Can anyone help with the spring specs? Should the springs on each side be the same and who can supply them? I'll rig up something to set up the advance curve but I want to check what springs should be present first. Thanks for any advice and specs.

You can see that the long spring with the heavy coils (arrowed) isn't doing much - the pin only comes into contact with the housing when the advance mechanism is almost at the end of its travel...... It looks like it's just used as a soft stop to set the maximum advance (there's no other mechanism to set the maximum centrifugal advance).

Matthew,

Welcome aboard.


IMO there is only 2 ways to check the springs and working accuracies. On the engine running at the various rpms, and/or on a Distrbutor Machine. I have never found a way to "look at" the springs/wieghts/mechanisms and determine whether they will work properly or not. Besides the springs, there are also shims to compensate for spring tension differences.

My procedure on Distribs goes like this:

Hook up timing light, check one bank all the way up, then check other bank, send out to Don Rudd for rebuild and Distrib Machine Calibration if not working correctly. At the same time have new points installed or optical pick-up aligned.

Open UPS package, reinstall, set timing both banks, recheck, done.

Regards, JRV

JRV,

Thanks for the reply and the welcome. Sure - I'm not trying to set the advance curve by looking at it! - I'll rig up a home-made (but accurate) dizzy tester...... I'm just trying to check that the long spring with the thick coils is correct. It looked odd to me at first partly because it can't be compressed much before it is coil bound and it is very stiff but thinking about it, it does appear to simply set the max. advance........ I'll re-assemble with the springs and shims as they were and test the curve both before and after fitting. Of course, the car and a good timing light is a pretty good distributor tester....... Fortunately this distributor uses the factory marelli electronic ignition so no points to worry about - just the pick-ups whose electrical insulation doesn't last very well. It's not easy to find someone with a distributor tester near here though - hence the need to rig up my own device......

If you have access to FCA Prancing Horse #68, I did an article on distributor rebuild with photos there. The subject Daytona distributors had deep holes for the long springs. The small washers are used under the springs to adjust advance curve operation to within 2 degrees of spec by changing spring tension. As JRV says, a distributor machine is best as you can make corrections without having to pull the distributor back off the engine each time, but an on-car test will suffice too, just more time required.