Marelli S121A Replica

[chris_seven]

The Marelli S121 fitted to the 911R is a very interesting distributor but can create fitting problems.

The original, and very rare, unit was designed to work with a small diameter 904/906 sized fan and if you try to fit it to a 2.0 litre engine with a standard fan housing it doesn't clear.

We are planning to make Replica distributors and we have just had the first casting delivered.

We have made it so we can make a 'standard' length distributor or add about 20mm to the shaft length so I will clear the standard fan housing by sticking out a little further.

Here is the basic casting.

I will post more photographs as the project progresses.

[gled49]

The reason the distributors don't fit is not the fan housing support, as they are the same for small and large fan housings. The distributor angle on Alu cases is 45* and race cases changed the angle to 47* for distributor clearance. Some Alu cases have enough casting shift so the distributor will clear. The fan housing support on Alu cases with this shift have real thin supports on that side. Mag cases have the 47* distributor angle built into the case from the factory. The Mag case fan housing support can be so thick that the distributors will not fit in those cases in spite of the 47* angle. Gled

[chris_seven]

I was aware of the angle change on the Aluminium cases but the S121A that I have is just long enough to clear the mounting flange on the case but does touch the standard fan housing.

I also have a 904 fan housing and it just clears with this fitted.

I agree changing the mounting angle would help.

Adding 20mm to the shaft length eliminates all of these issues.

[andrea70]

Fantastic Chris, as usual!

[Brad Davis]

Chris,

Very excited to see this project in the works. Great work as with all you do.

Brad

[kenikh]

Here's hoping the price is right!