Thread: spark plugs
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les_garten les_garten is offline
Macht Schnell
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Join Date: Jun 2003
Location: PSL, FL
Posts: 861
Hi Doug,

First off, all these remarks pertain to mildly driven Street cars. Which is how most 930's are driven.

NGK 6's are two steps colder than the Factory plugs(NGK 8 Heat Range). My recommendation would be drop a 7 Heat range NGK in there(That's what I am running in mine). Watch them for a while. Put some miles on them after you get your new goodies all tuned up. Then pull the plugs and see whether they have signs of being too hot. I believe 7's would in no way be too hot. Then decide whether you would like to go for a 6 range plug.

The factory plugs(NGK 8 Heat Range, Bosch 3 Heat Range) are just too cold for us folks who don't drive to work on the Autobahn everyday. Here's the plug I use and would recommend for you, NGK R5671A-7. These are NGK Race plugs. Every speed shop in the world stocks these, they are cheap, and they are Race plugs. If you go to a Hot Rod shop, they'll tell you they sell more of this series of plugs than anything else, at least that's what mine tells me. I know a guy who routinely builds 900-1000HP 930's and this is what he uses. One huge advantage is that if you are playing with Spark plugs, you can get these at Pep Boyz, Napa, Advance, etc.

Cons of Platinum or Iridium. $15-20 per plug!! These NGK's can be had for under $2.

There's gonna be folks who don't like "JAP" plugs in their Teutonic Road Warrior, or have stories of this plug or that plug fell apart. I've pretty much used Bosch, DENSO, and NGK for over 30 years and can't see much difference in "Street" applications among them. The DENSO irridiums do last forever, or damn near forever. However, most 930's get their spark plugs changed "really" often, and a 100,000 mile spark plug is not needed.

So my feeling is why would I spend $15-20 a plug when I can't tell the difference from a $1.79 plug. The $1.79 plug is lighting my mixture perfectly. NGK race plugs are not poorly made spark plugs either. That's what I have always used in my Motorcycles. The current one is German also!

The only difference I might do is once my tuning is "totally" sorted out. If that day ever comes!! I would change to a DENSO Iridium. I have them in my Land Cruiser. I changed them at 70,000 miles and they looked like they were new. That translates to me as being no change in Gap or performance in 70,000 miles. You have to be impressed with that.

Sorry for the long post. Spark Plugz are a Political/Philosophical discussion and can get long winded. The above observations are my experiences, others may differ.
---Les Garten---85 930, Andial IC, GHL Headers, Fabspeed Dual, K-27 HF2, 3.4 JE Full Finned 7.5:1 CR, 964 CAM'd, Carerra 3.2 Manifold Cut/Flipped, Tec3r, Siemans 55#, GSF Fuel Rails, Clewett Crank Trigger, Clewett Cam Trigger,Dual Plugged, ARP Head Studs/Rod Bolts, Clewett Wires.Tial 46mm WG, Tial 50mm BOV, WEVO Shifter,934 Boost Gauge, Wideband EGO Sensor/Gauge, C2T Head Gaskets, '88 MB 300TE,BMW R100RT
Old 03-03-2008, 11:27 AM
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