Postby Brake buster » Fri Mar 30, 2018 9:25 am
firstly
be wary of aftermarket items for the V12 ignition , especially Marelli replacements ,
if you dont understand the way the V12 Marelli system works you will end up throwing lots of parts and money at the engine without knowing if and what you may have fixed , and will be none the wiser
a GOOD condition Marelli system is a perfectly good ignition system , the so called ' Marelli fire' issues come from incorrect spark plugs, not gapped correctly and poor HT cables , and poor maintenance , high resistance in the system ( from bad spark plugs and poor HT leads ) causes the Distributor cap to burn out, causing running issues and unbent fuel entering the exhaust onto a hot Catalitic converter, hence the fire,
btw UK cars do not have a CAT , and we dont get the fire ( just back fire , lol )
one thing to note, the spark plugs out of the box need re-gapping, this will improve and provide consistent combustion , i have original Brass Genuine Marelli distributor caps if you need to buy one ,
i presume you mean the modification to the top of the rotor arm , this is a known worthwhile modification to prevent issues should the ignition system develop problems ,
the distributor intake filter you mention needs to be there, the dizzy body has a vacuum pipe from the manifold, and then a pipe to this filter, this draws air through the dizzy body to the intake manifold, this prevent the build up of Ozone gas within the dizzy which corrodes the metal parts, Ozone is created from lightening , such as the electrical discharge from the posts to the rotor arm even time the cylinder fires , any small filter type device will suffice , as this air does go into the engine unfiltered otherwise
hope this helps
BB
ps, i have been running and maintaining my own V12 marelli system for 15 years
1994 3.2S in Morocco red and Doeskin/Ruby red interior
1989 V12 XJS White with Mulberry interior
2015 XF Sportbrake Luxury 2.2D Turbo in British Racing Green Metallic