2.0litre 911S Spark Plugs and Coil

[gruen911]

Guys,
My new mechanic is telling me that the 2.0 911S engine used specific plugs that were different from the other early 911 models. Can anyone confirm this for me? If so, what plugs should I be using? Also, I am wondering if the 66-67 911S used a different coil from the other 911 models.
Can anyone confirm and/or clarify. Thanks.

[kenikh]

Why the HELL are W3DPO plugs $12 more than other 911 plugs (like the W5DC)? Are these plugs a must have for the 2.0S or is it a scam? I know I am splitting hairs over a few bucks here, but if I tune up my car every 6000 miles, it gets expensive. Are there any equivalent, cheaper plug options?

On that note, how often do you guys swap out rotors, caps and plug wires?

(edit) I just cancelled my W3DPO order that I placed with Pelican. After doing some searching on Peilcan and here, it seems there are mixed opinons on these plugs being too cold anyway. Steve at Rennsport suggested the W5DS as a better plug and is hopefully cheaper. Pelican doesn't carry these. Anybody know where to get them?

[B D]

Just get spark plugs from any auto or motorcycle shop no need to order and pay shipping.

Here are some base miles for replacing ignition parts, but I prefer to inspect and check them often and replace when worn.

Plugs: 10,000 miles
Cap: 10,000 miles (less with MSD due to multiple sparks)
Rotor: 10,000 miles (less with MSD due to multiple sparks)
Points: Ditched for a Crane optical unit
Plug wires: check for cracks, arcing and resistance
Distributor Shaft lube: 3000 miles

[roblav]

The W5's worked great for me years ago. The 3's are too cold. But I just purchased the NGK 7's for my 1966 (also purchased CD unit and coil, Pertronix, Magnecor). Will start out at .040 plug gap.

[gruen911]

If you note above, I was the guy who started this thread back in November of last year. Sithots advice about the NGK plugs was good.
After switching to NGK B7ES plugs and an MSD 6AL ignition and blaster coil back in early Spring, all of plug fouling problems are long gone.
In my humble experience, the NGK plugs are the way to go. They seem to be every bit as good as the more expensive Bosch plugs, but when you can buy 6 NGK plugs for the price of one Bosch plug, the decision is easy. Besides, I like to look at my plugs every once in a while to see how well my engine is burning fuel.
IMO, Bosch products are overpriced and over appreciated compared to other US and Japanese competitors. When you can get a brand new MSD CD unit for $250 or a 30 year old used Bosch unit for $500 that doesn't throw anywhere close to the punch of the MSD set-up, it makes you think hard about which way to go - originality versus performance. I prefer the look of old but the performance of now. Since the MSD is stuffed behind the air cleaner and practically unnoticeable, it doesn't seem to make any difference.
One other point, the early 2.0S didn't even have a CD box until 1969 so any CD unit would be incorrect for the pre-1969 911's.
With all of the plug fouling problems that the high strung 911S's had back then, if the MSD technology had been around back in the 60's, I would have to believe that the wrenches at Porsche would have jumped on it.

[nick-moss]

Thanks guys, very useful information. On the ignition front I have recentlty had high rev misfire problems with both a 68 911 and a 69 911S. All problems were solved by fitting a Bosch CDI unit (I seem to have a few lying around) with a custom loom. The only problem is the Tacho which needs converting. Did anyone ever come up with the loom/diode modification details?

[rick2]

I can't help with the loom. I did though find out a hint years ago that may help someone...to get a hotter plug in bosch increase the number, ie w3's are colder than w5's and so on but the ngk's are opposite decrease the # meaning to get a hotter plug from b7's got to b6's and so on. The only note is if your application calls for bpr7es then use bpr6es for a hotter plug. The first letters describe electrode shape and if a resistor plug and the other letters at the end describe electrode depth.

[spydr32000]

I have found the Beru Z22 plugs are a good option they are compatible with NGK BP7ES, the warmer option is Beru Z20 = BP5ES, these plugs are comparable in price to NGK's and at least as good!

[Ed B]

W3CPO plugs have large platinum center and ground electrodes. They last forever. I have 70K plus miles on my original plugs. The electrodes don't erode. Have to use them with a CD ignition though. Original plug was W265T2SP (platinum/silver). Running to hot a plug, (range 5 or 7) may burn a piston.

Ed B

[304065]

Ladies and Gentlemen,

The 1964-1968 911 used "Kettering" ignition consisting of a battery, coil, points and condenser. In 1969, the Bosch CDI (or BHKZ) was introduced.

Nick Moss: The early tachometers are what electronics engineers call a "one-shot" or monostable multivibrator. When a tach signal pulse is received, it is converted into a signal to fire a transistor which conducts current that flows through the meter movement for a defined period of time. The more frequently the pulses occur, the higher the tach needle bounces, and the pulsing is "integrated" by the movement of the needle.

Unfortunately, the early tachometers (pre-72) trigger off about a 40V pulse with plenty of inductive ringing and noise. Since the current flowing in the trigger circuit of the Bosch CDI is only about 420mA and 12V, it's not enough to trigger the old style tachs. Bosch came up with an "intermediate unit" which came stock on the 1969-1971 cars, it's basically a coil, resistor and capacitor (I haven't figured it out exactly yet but I'm working on the reverse-engineering) that generates an inductive voltage spike when the CDI fires, triggering the tach. Not super accurate and VERY sensitive to system bus voltage in my experience. I have a Bosch CDI in my '66 and use that system to trigger the tach.

In a few days I'll post on pelican some pictures of how to retrofit a modern VDO movement and tach board to a green-number tach. I have also been working on making my own tach driver board from an LM2917 chip but racing has gotten in the way of that project. . .

For more than you ever wanted to know about early car ignitions here are some links:

http://www.early911sregistry.org/for...ad.php?t=10817

http://forums.pelicanparts.com/showt...hreadid=252299

http://forums.pelicanparts.com/showt...t=ballast+unit