rebirth of a Ferrari

tale of a thirty three year old 308GTB

Copyright © 2013 by Ron Smith. All rights reserved. Rebloging and personal use is however encouraged.

Magneti Marelli

A few years ago, I took the Ferrari out for a spirited run, and when making an aggressive 90deg right turn, I immediately got a dead miss on at least one cylinder.   I pulled over, and took a quick look under the hood, but did not see anything obviously amiss. Fortunately I was not too far out to simply limp back home. 

Suspecting ignition, I found my problem in the first place I looked.  When I pulled the distributor cap I saw this.

 

The top bearing of the distributor shaft had lost all of it lubrication and worse yet is was rusting. It had been self destructing forming a small mountain of metal chips.  On the 308 the distributor is mounted horizontal. So the first hard right turn, tossed the pile of metal chips right into the cap promptly shorting out #1 cylinder.  The spark was following the trail of metal chips to ground.  The next few photos show rebuilding of this distributor.  

 

 

Although the car ran OK, when I was done, I was not totally satisfied with my rebuild because I could not check the advance curve.  The “seat of my pants” dyno felt that the 308 was not pulling as crisply as it had in the past.  

I sent the distributor to a Ferrari dealer in the north east, and two months and $800 dollars later I was still not happy with how the car ran.  I ignored this for a while, until I discovered Marelli Service. 

Tom Meadows has been rebuilding, tuning and servicing Marelli dizzy’s for years.  After a short friendly conversation, I sent him the distributor, and all of the MSD electronics.   

This distributor is a single distributor conversion done when the engine was rebuilt by IFS ( http://308gtb.tumblr.com/post/3057622913/a-little-history-about-this-car ). US bound 308’s of my vintage originally had two distributors, each with two sets of points.  It is a nightmare of complication for very little gain in performance, especially if you have upgraded to a high output modern ignition coils and CD systems like the MSD on this car. 

Many driver cars (cars that folks drive vs. kept original for car shows) have been converted to a single distributor set up with electronic ignition.  Tom at Marelli Service has seen many over the years and has converted a few himself.  He told me this conversion was in many ways, one of the nicest he had ever seen, and made a point to get all of the details of the conversion. 

He made all the adjustments to the advance curve and the distributor is now back in the car and she is running great!

This is the advance mechanism. It is rather complicated, considering most other distributors simply have springs that are in tension and resist centrifugal force of weights.  This uses compression on a drum, with pins, sleeves, two springs per weight, and a bushing in the cam slot (you can see in the black “arms”).  That is 18 parts where others manage to get by with only 5.