Bosch spark plugs

[arcturus]

Hi, found these in my garage set of four new but can't remember what they are for,any ideas?Note that Bosch now manufacture in Russia! makes a change from China

[classicswede]

With no numbers hard to say but thread length looks about right for B18/20. Ok as a spare but Bosch can be very unreliable

[FrederikL]

It looks like WR5BC plugs, before that we had W5BC and W5B. The one missing a "R" means it was without a built in resistor and the "C" is for cooper core plugs (they came about in the late 70s and at the same time Bosch started manufacturing plugs in India). In the old Bosch part numbering system from when the cars was new W5B was called W225T35. (See Bosch recommendation table from 1970 for Volvo cars).

By the way, the numbers are the heat range, going cold to hot, new (old number): 5 (225) ,6 (200), 7 (175), 8 (145). With NGK the numbering is the other way around, 5 being warmer than 6 and so on. For some cars you need a warmer plug today than the old reference to avoid fouling.

There are still lots of good old NOS German made bosch plugs out there (I have a lot of them), but the "new" Bosch plugs many stay away from. I guess it started when they outsourced manufacturing..

[arcturus]

Yes, these were made in Russia of all places,Probably have a bug in them for eavesdropping:)