WR7DC vs WR6DC
 

When I pulled the plugs in my 79 motor it had WR8DC, but I am thinking the stock plug for all the 16v motors is the WR7DC. WR6DC seems to work for some people as well, any opinions?

Run the coldest plug you can without fouling.

WR8DC is listed as the correct plug for OB's in some places. Porsche switched to 7's with the 4.7 and kept the same heat range through the GTS.

I've been running WR6DC plugs for a while now under boost with no issues. I'll be installing 5's this spring, see how that goes.

Sorry rogue, I had no idea where that pan (or the picture) came from.

Just one of many pictures on my computer of busted up 928 engines I've "collected" over the years.

******** has plugs for I think $1.35, so I was thinking of getting some of almost everything.

I wonder if Porsche didn't use the hotter plug to stay away from intake oil issues fouling the plugs?

That would be my guess. My oil vapor no longer goes into the intake.

I run heat range 5 in the turbo cars. For NA I would stick with 7 and stick with copper or silver electrode. Platinum's only advantage is its life.

My engines are a stock 84 Euro S, and a stock US 83 S. The Euro has a fresh set of WR7DC plugs, not sure what or how old in the US 83.

Colder plug on the Euro S I am thinking might allow a bit more advance running the 91 octane gas thats as good as it gets in Calif.

BTW whats with silver, sounds goofy for a spark plug?

Silver is one of the best conductors...platinum has a lower thermal and electrical conducivity than silver or copper. Copper is the best bang for the $.