Here we go! Sorry about the wait as I have limited use to a camera. Early this year I manufactured a rotor for the Marelli twin plug distributor. For those that do not know, the Marelli twin plug distributor was fitted on all racing applications up until 1972. The venerable 906 as well as the 911R, 911 ST and 911 2.8 RSR all made a home for this high quality piece. A very robust unit, it utilized lower and upper sealed bearings for longevity. The only problem with it was that it had a tendency to bounce points at high rpm.
FYI, this distributor should not be confused with the single plug unit found on the regular 911 !
The prices of the original cap and rotor for this distributor are extremely expensive. Old stock can command $700 dollars for the cap alone! Replica caps and rotors retail for $800.00 to $1,000.00 depending on the exchange rate and markup. Pic of the replica cap and rotor below. Notice the carbon brush on the rotor.
I decided to make my own rotor that works in conjunction with a much cheaper cap found in the mid 1990s Jaguar 12 cylinder car. The bolt pattern of the cap is identical with the original version but is a slightly different design. Both the Jag cap and my rotor are a direct bolt on for the picture above. Here is a pic of the jag cap and my rotor.
This substitution allows for a much lower operating cost and hopefully increased demand for entry level conversions.
Since a single plug distributor does not share the same dimensions as its twin plug brethren, you must convert it with adapters so that you can bolt on the cap and rotor. There are a number of solutions in regards to twin plugging your engine. The least costly is the conversion of a single plug unit (Bosch) that came standard on the 911 in the late seventies. These types of conversions are generally cheaper initially but may require more frequent service of the bushing.
You can normally have a dizzy converted by an engine builder. Here is an example of a Bosch unit the expensive Bosch cap and rotor. It is from one our members in the classifieds a while back.
The 964/993 distributor can also be installed but will not work in a turbo application. If you are not concerned with aesthetics, this a fine route to go.
The mid level solution is a replica distributor. There is one out now and mine is on the way. These are purpose built and use the latest in pointless ignition systems.
The highest level is the original Marelli (see first pic) that varies in price from $2500.00 for one in fair condition to $6000.00 for an NOS example! Expect limited duty with the originals as these have 40 year old parts. The lower bearing as last I heard is special and in no longer available. Carl Thompson does have quite a bit of parts for them, but don’t expect a deal as they are exclusively priced (as they should be)…
There are distributorless ignition systems that are available and give the best is drivability, performance, etc, but I have focused on distributor type applications for obvious reasons.
This post is a work in progress and I am sure I am missing some aspects which I will add when notified of when I can think of them. Prices are not included as they vary from application to application. I am working out agreements with a few stores with Pelican being one of them. (edit)Feel free to P.M. me for purchasing caps and rotors untill then. P.M. me with conversion questions for you application.
Thanks guys!