Lizard944

I have a 1986 (mfg. date 7/85) 944n/a. All catalog references, and even the dealership, state that I should be using WR7DC or WR7DP plugs. Problem is that my engine compartment sticker says I should use WR8DS. I've been using WR7DP for a long time, without any problems, and recently switched to the DC's because I think copper is a better conductor. Anyone else have this sticker discrepancy?

scular

Lizard944, didyou ever find an answer?
I knew someone else had to have been in the same situation before, I have been working on this for the last hour.

The sticker in my car (86 944NA born Oct. 85) says Bosch says WR8DS or Champion RN10GY. Okay no biggy there. Haynes manual (taken with a grain of salt) says the same and the WR7DC is for the 2.7L engine. Porsche shop manual agrees. Now when I goto the local rejects house, I mean parts store, they say WR8DS doesn't exist. So they look it up by '86 Porsche 944Na, and the computer(which is always right) says WR7DC. I say no thanks, I want to double check my manuals

Continuing on I cross reference the part numbers on autozone.com and napaonline.com and this is what I get:

WR8DS(magicially it appeared in there own reference tables, go figure): Autolite ASP65, Champion Cha322, NGK NGK3971

RN10GY: Autolite ASP63, Bosch Super 7506

WR7DC: Autolite ASP64, Champion CHA415, NGK NGK7131, Bosch Super 7501

Now I have put about 20,000 miles on the Bosch WR7DC plat. 4's and about 20,000 miles on the regular Bosch WR7DC, both sets of plugs appeared to be running to hot. Now I am beginning to pull out my hair, can someone please help me decipher this mess. I don't want to get into platinum vs silver vs copper or to use anti-sieze or not, just what is the right number to go off. By the way at least 85% of my driving is above 65mph on the highway, sustained for about 2hrs.

thanks

IanM

I'd stay with copper for starters.
The 7 versus 8 refers to the heat range of the plug. For some brands the higher the number the colder the plug, for other brands it's the opposite. First find out which is a colder running plug, 7 or 8.

If you've done lots of mods, and your car is putting out way more hp than stock, then you should go with the colder plug.

If your engine is old and tired, then use the hotter plug.

stefang

Just went through the same thing. On Bosch plugs the higher number means hotter. NGK is the opposite. I decided to go with factory heat range and drop WR8DCs into the car. After (perhaps during) my next track day I'll pull them and check too see if they're running too hot. I figure at $1 a pop I can afford to toss a few sets looking for the right heat range.

Stef

Eric D

What do you look for on the plug to see if it is too hot?

stefang

According to Haynes there seem to be 2 options for a plug that's too hot:
"Blistered, eroded electrode and absence of deposits" or "Insulator has yellowish, glazed appearance". Normal is "Brown to grayish-tan color"
Too cold would be carbon deposits. The basic idea is that the plug gets hot enough to get into the self cleaning range.

Here's some more info: <a href="http://www.ngksparkplugs.com/techinfo/spark_plugs/overview.asp" target="_blank">http://www.ngksparkplugs.com/techinfo/spark_plugs/overview.asp</a>

Stef