spark plug recommendation with ignition system upgrade please

wareaglescott · wareaglescott's Garage

Car - 79 SC stock configuration

I am upgrading my igniton system from stock to a MSD 6AL and the blaster coil. New Beru distributor cap, new rotor and Clewett wires.

Looking for a recommendation for the proper spark plug to use? I am pretty new to this stuff and really dont have a good understanding of all the spark plugs.
When I originally bought the car I bought Bosch WR8 DC+ per Pelicans recommendation. Is this appropriate or what should I use?

Thanks for the assistance!

T77911S · 04-12-2019, 05:11 AM

plugs should be matched to the engine. more specifically the compression ratio (and boost if turbo). also driving conditions and engine condition on a lesser part.

wr8 is a pretty hot plug. I would drop down to a wr5, then pull them and inspect after 100 miles.
then work your way up to hotter if the plugs don't look good.
but take into consideration driving and engine condition. if rings are bad you may need a hotter plug, if you do a lot of idling in traffic you may need a hotter plug.
if hiway droving you can go colder.

the heat range of a plug is designed to keep it clean. that's it only purpose.

get a resistor less rotor. some have burned up.
I have used a BDW D163

mount the coil right side up.
I had clewett make me a special coil wire so I could leave it in the original location but right side up. I also had a 90 put on the coil end so my coil still sits under my intercooler.
if you don't have the wires yet have him put numbers on BOTH ends. trust me, it will be nice.

wareaglescott · wareaglescott's Garage

Good info thank you. I did read about the rotor issue and was planning on that.

I am a novice and learning as I go. Does the ignition change to the MSD dictate a different plug itself or would the plug recommendation be good for whatever ignition was on the motor be it stock or msd?

jamesjedi · 04-12-2019, 07:16 AM

There is a great deal of information on this. The cross reference chart is helpful.

See post #7;
NGK BP8ES vs. BP5ES

wareaglescott · wareaglescott's Garage

Thanks James!

I looked here
https://partcat.com/ngk

It recommends the NGK5 which appears the same heat range as the Bosch 8 I already have.

Buddy mentioned he thinks the NGk are "resistor-less" which he thought he remembered being better for the MSD and the Bosch is not.
Anyone know about that?

jamesjedi · 04-13-2019, 06:20 PM

There is some great information here. Neil Harvey makes a few posts;

Spark Plugs

T77911S · 04-15-2019, 09:00 AM

8 is probably too hot for that engine. start with a bosch 5

merlinfe · 06:30 AM

I ran a MSD Street Fire, High Vibration coil, stock distributor cap, resistorless rotor, and Magnecore wires on stock 1983 911sc copper plugs gapped to .040" . NEVER had an issue.

My .02.

- Steve

Reiver · 04-16-2019, 07:37 AM

I use NGK's with an MSD box....but the same recommendation that Porsche indicates...I have a 9.8-1 930-10 so use a colder plug than you do. With the MSD you can open the gap a tad.
Rotor...Napa Echlin EP407....looks exactly like the Bosch unit without the resistor element...perfect fit.

wareaglescott · wareaglescott's Garage

Quote:

Originally Posted by Reiver

I use NGK's with an MSD box....but the same recommendation that Porsche indicates...I have a 9.8-1 930-10 so use a colder plug than you do. With the MSD you can open the gap a tad.
Rotor...Napa Echlin EP407....looks exactly like the Bosch unit without the resistor element...perfect fit.

Friend recommended the same rotor. I went down to Napa and they had to special order it and required me to pay the freight. Said it is not an item they normally stock. Thought that was strange so got two of them. Maybe they are going to be hard to source in the future. Guy behind the counter also indicated some strange models that it was meant for. Nothing VW/Porsche. My buddy confirmed that was the right one so just waiting for them to show up.

Reiver · 04-16-2019, 01:56 PM

Quote:

Originally Posted by wareaglescott

Friend recommended the same rotor. I went down to Napa and they had to special order it and required me to pay the freight. Said it is not an item they normally stock. Thought that was strange so got two of them. Maybe they are going to be hard to source in the future. Guy behind the counter also indicated some strange models that it was meant for. Nothing VW/Porsche. My buddy confirmed that was the right one so just waiting for them to show up.

I've been using them for years now...I ordered a bunch last time but check the box/rotor when you get it....they sent the wrong ones in the right box once.