I'm doing a tuneup on an 85 1.9L engine that had about as much power as any
2.1L i've driven. it's a 1.9L case but might have bigger pistons or
something. anyway, i took the plugs out and they are Bosch W8DC. most
vendors sell the W7CC or WR7CC. bus-boys.com shows a W7DTC for the 85 only.
No other 85 I've worked on has had any bosch plug other than a W7CC. does
anyone know why bus-boys and the previous owner of this 85 feel that the
85's need the W_D_ _ plugs that have a less shielded spark thats also a
little further into the cylinder? the threads arent longer, just how far the
electrodes are from the threads.

www.boschautoparts.com/NR/rdonlyres/C77B3446-232B-4AEC-AFA9-AD05F2A0A2AD/0/DesignationCodes.pdf