I recently purchased a set of plugs, wires, cap and rotor for my '72 350SL (4.5L). All Bosch parts. I relied on vendor who quoted OE type parts.
The rotor and cap are fine.
The wires are Bosch Premium part 09027 which is what catalog on Bosch site comes up with too, if you look for the part number. But, these wires are called Opti-Layer Mag and it says they are nickel alloy or stainless steel spiral wound.
On the top of the box, it says they are for MB 8-cyl engine.
On side of box, it says "Stainless Steel Mag winding(*) for hotter more powerful and longer spark" But the asterisk leads to a footnote that says For American and Asian cars only.
I don't know if they mean that they should only be used for these cars or if they mean that they are only S/S for those cars?
Plugs sent were Bosch WR7DC+. Number was 7500
0 242 235 663-74U
Original Bosch plugs were W175T30, but more recently we used W7DC and I believe they also had the 7500
number while WR7DC plugs were 7501
) Maybe the "+" means something?
I measured resistance of original MB plug wires - They had a resistor built at the distributor end, not sure about other end. Overall Resistance was 8kohms. Did same for new wires and they are 1.6 kohms (meter may be a bit off).
So, I come to my questions:
- Are these Bosch wires right for my car?
- Is the wire/plug combination right for my car?
If unsure, is there a way to get a definitive answer somewhere? I am sure MB would tell me to buy their wires and whatever plugs are equivalent to the OE. But, would even that be right, given some progress since 1972?