Spark Plugs choices for 67S

[behyar]

My 67S with the stock ignition came with the Bosch W5DC spark plugs when I got it, but the documentation talks about the W3DPO. I now need to replace them and was wondering what to get.

I am also thinking about switching to a CDI unit. Would that change the choice of the plugs?

Behyar

[Steve@Rennsport]

Hi:

IMHO, the W3DPO plugs are too cold for these engines unless they are being driven flat out for a long time.

You can get away with those plugs if the car has an MSD ignition system and matching coil.

I would use W5DS with either ignition setup for all-around usage and W4DS for track use. These are silver plugs and have a very wide heat range.

[behyar]

I cann't seem to find the Bosch silver plugs anywhere. They must have been discontinued. What is the downside of running cold plugs beside the big price difference?

[Steve@Rennsport]

Running plugs that are too cold for the application results in poor running and a loss of power.

The silvers are usually a special order and few outfits stock them. Its a real shame as they are really better than the old style platinums (DPO).

If you cannot find them, please e-mail me directly and I'll get you a set.

[Lee]

I couldn't agree more. I've used nothing but the silver plugs for years. THey last longer than the old platinums, and cost much less. I've not tried to buy any for a while, so if they are becoming hard to get, please let me know where to find them!

Relative to the heat range (W3, W4, etc), that's independent of the electrode material. I also agree that a W3 is a bit cold for anything other than racing, but I would probably not go beyond a W4.

Lee