Spark plugs

356 Porsche-related discussions and questions.
Message
Author
User avatar
Charles H Jacobus
356 Fan
Posts: 493
Joined: Wed May 28, 2014 5:02 pm
Location: Dallas, TX

Re: Spark plugs

#16 Post by Charles H Jacobus »

C J Murray wrote:I apologize for posting this but it just had to be done. Get out the Tylenol.

https://www.vdlfuelsystems.com/anything ... ark-plugs/
Thanks CJ I actually thought that was quite interesting. Given the article, there's bound to be a plug that is better for CDI ignition verses standard and I'm looking for a CDI (6V Winterburn) one as well (with a source).

Chuck
Last edited by Charles H Jacobus on Thu Nov 16, 2017 8:11 pm, edited 1 time in total.
Current:
2012 Silver 991
1995 Midnight blue 993
1965 Red 356C

Past:
Fond memories of 14 others (including a '63 Normal and a 61 S90) :)

User avatar
C J Murray
356 Fan
Posts: 9158
Joined: Fri Oct 23, 2009 7:24 pm
Location: 30MI WEST OF PHILA
Contact:

Re: Spark plugs

#17 Post by C J Murray »

Thanks Chuck, I like it but it may be too much for some people. My advice is to use the standard NGK plug without the whistles and balloons. They work fantastic regardless of what ignition you run.
'57 Speedster
'59 Sunroof
'60 Devin D Porsche Race Car
'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
'09 Smart Passion

Jeffrey Leeds
356 Fan
Posts: 1280
Joined: Sun Apr 20, 2008 4:57 pm
Location: Northeastern MA

Re: Spark plugs

#18 Post by Jeffrey Leeds »

I particularly liked the following excerpts selected from Cliff's reference:

"The addition of ethanol in our gas at the pump has now created moisture retention concerns as well and has introduced corrosive characteristics to the fuel that WILL destroy your entire fuel system over a season."

"One last thought: there is no such thing as using aviation fuel. Aviation fuel is designed for high altitude and is not a high performance fuel."

Jeff
< Jeff >

Registry Member Since 1978
1963 356B T-6 Super 90 Coupe
2009 997.2 Carrera S
2015 958 Cayenne diesel-1 & 2015 958 Cayenne diesel-2

Fred Winterburn
356 Fan
Posts: 106
Joined: Wed Sep 13, 2017 6:31 pm
Location: Ripley, Ontario, Canada
Contact:

Re: Spark plugs

#19 Post by Fred Winterburn »

There are two types of spark plugs that I do not recommend for use with the CDI. The first is Champion resistor spark plugs. The resistors are weak (or used to be 25 years ago) and the CDI will make short work of them. The second spark plug that I don't recommend is the Bosch Platinum as shown in the picture. They are really poor with this CD ignition. My younger brother says that a high energy ignition will sputter off the platinum and leave a carbon core in its place. My theory as to why they don't work well with the CDI is the complete shrouding of the centre electrode except for the very tip. My theory is that the small surface area makes the spark plug behave like a rectifier which suppresses positive going sparks (this CDI spark alternates polarity a few times during each spark event). For whatever reason, that style of platinum plug does not work well.
I did not realize that my Volvo(B18B) and Morgan(TR3 engine) use the same spark plugs as the Porsche. If that is the case, the two plugs I use successfully with the CDI right now are NGK BPR6HIX on the Morgan, and NGK BZ7HS-10 on the Volvo. The latter plug is actually designed for outboard motors, is one heat range colder (OK with the CDI) and has an inductive rather than resistive suppressor to take the extra abuse of CD ignitions. Having written that, I have found that NGK resistors are robust enough to take the extra abuse this CDI can give (unlike the resistor in the Bosch rotor that will fail given time) Fred

Alan Hall wrote:I have never run platinum plugs but have seen a few and I believe the center electrode is solid platinum, not plated, but is a VERY small diameter wire held in the ceramic. See photo of a bosch W8AP platinum plug.

User avatar
David Jones
Classifieds Moderator
Posts: 7323
Joined: Tue Mar 25, 2008 6:32 pm
Tag: I wish I knew as much as I think I know.
Location: Kentucky

Re: Spark plugs

#20 Post by David Jones »

The NGK BPR6HIX is my next buy in spark plugs. I posted a link to it earlier and I ordered a set off Amazon then I see that Fred is running them so I am happy I have concurred with his choice. Not that I have had any particular issues with plugs. All mine seem to be with carbs and running off road when I shouldn't.
Last edited by David Jones on Mon Jan 15, 2018 2:27 pm, edited 1 time in total.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715

User avatar
Bob Slayden
356 Fan
Posts: 136
Joined: Tue Mar 25, 2008 8:42 pm
Location: Sandy Springs, GA
Contact:

Re: Spark plugs

#21 Post by Bob Slayden »

I am running Fred Winterburn's CDI 6v system in my '62 roadster. big bore, otherwise 912 engine along with 123 ignition. I have my electric fuel [pump primer system that I wrote up years ago installed. My engine runs exceptionally well, starts immediately, great power and no hesitations.
My issue has to do with spark plugs. Currently I am running Bosch WR7BP (platinum) but according to Fred I should avoid platinum plugs. David Jones refers to NGK BPRIHIX but I can not find that number. I can find BPR6HIX iridium plugs that Fred mentions. I am unclear if that would be a good choice heat range wise or perhaps the NGK BZ7HS-10 (a solid copper core nickel tipped electrode plug.) Since Fred has thoughts about platinum sputtering would that also apply to nickel tip sputtering?

Bob Slayden


From Amazon:
NGK (3579) BZ7HS-10 Standard Spark Plug, Pack of 1
4.7 out of 5 stars 7 customer reviews
List Price: $5.70
Price: $3.72 Free Shipping for Prime Members
You Save: $1.98 (35%)
Get $70 off instantly: Pay $0.00 upon approval for the Amazon Prime Rewards Visa Card.
In Stock.
Want it tomorrow, Jan. 16? Order within 3 hrs 6 mins and choose One-Day Shipping at checkout. Details
Ships from and sold by Amazon.com.
Designed to operate over a much wider heat range than ordinary plugs
Resists carbon buildup and pre-ignition
High alumina ceramics for better heat transfer and electrical insulation
Solid copper core and nickel tipped electrode provide a longer plus life
Patented triple gasket sealing process eliminates the possibility of combustion gas leakage

User avatar
David Jones
Classifieds Moderator
Posts: 7323
Joined: Tue Mar 25, 2008 6:32 pm
Tag: I wish I knew as much as I think I know.
Location: Kentucky

Re: Spark plugs

#22 Post by David Jones »

Bob, my bad. That was a typo, I meant BPR6HIX. #4085 which is what I bought. Seem to be an excellent plug so far. Also in reference to CJ's post on aviation gasoline. It is designed for low and constant rpm engines as well as for operating at varying altitudes. It has relatively low volatility so it will not boil at altitude and it is still needed only because modern automotive fuels are not compatible with high compression aircraft engines and have also not been certified to be used on aircraft engines. If you feel you must run a higher octane in your car then buy 93 octane at the pump. The ROZ or RON is about 99 octane almost the same as 100 octane low lead aviation fuel and racing gasoline is also available at far higher octanes and is designed for high revving fast accelerating automotive engines.

https://vpracingfuels.com/master-fuel-table/
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715

User avatar
Jim Liberty
356 Registry Member
Posts: 4312
Joined: Tue May 06, 2008 3:47 pm
Tag: Jim
Location: Orange Co., CA
Contact:

Re: Spark plugs

#23 Post by Jim Liberty »

NGK - BP5HS (4111) from a guy with less expertise than all of the above. My choice. .......................Jim.
Jim Liberty

User avatar
David Jones
Classifieds Moderator
Posts: 7323
Joined: Tue Mar 25, 2008 6:32 pm
Tag: I wish I knew as much as I think I know.
Location: Kentucky

Re: Spark plugs

#24 Post by David Jones »

Still a good choice Jim though I preferred the BP6HS, not that there is a lot to choose between them. I only bought the BPR6HIX because I cannot leave well enough alone and feel the need to experiment. Same holds true of using CDI though the practicality of points not burning up and the elimination of the ignition capacitor is a plus for me.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
David Jones #9715

Jeffrey Leeds
356 Fan
Posts: 1280
Joined: Sun Apr 20, 2008 4:57 pm
Location: Northeastern MA

Re: Spark plugs

#25 Post by Jeffrey Leeds »

I have been running the NGK BPR6HIX for 6 years (40000 + miles) now and am very happy with the outcome.
< Jeff >

Registry Member Since 1978
1963 356B T-6 Super 90 Coupe
2009 997.2 Carrera S
2015 958 Cayenne diesel-1 & 2015 958 Cayenne diesel-2

Erik Thomas
356 Fan
Posts: 403
Joined: Thu Jan 14, 2010 4:55 pm
Location: Rhode Island

Re: Spark plugs

#26 Post by Erik Thomas »

I have never had problems running the Bosch WR7BC in my 356 SC engine, with about 9.5/1 CR. I generally run super unleaded with the occasional does of race fuel or 100LL Avgas. I have had problems with the Bosch Platinum plugs in the past, though not in the 356. I never thought they were worth a damn, let alone the extra money. I have used Bosch plugs, pretty much exclusively, since 1977. I even run Bosch plugs in my MG's.

Erik Thomas
356 Fan
Posts: 403
Joined: Thu Jan 14, 2010 4:55 pm
Location: Rhode Island

Re: Spark plugs

#27 Post by Erik Thomas »

More... The dose of 100LL is at the end of the season, so the ethanol in the fuel is not eating away in there all winter, then going bad. This amounts to adding some lead into the fuel also, as 100LL is anything but LOW in lead. This stuff is also hard on plugs, but 5 gallons at the bottom of the tank once a year seems to do no harm. Some time ago, I modified my pre-war Mercedes 170 V engine to run on 100LL, as I could not get high enough octane fuel for it. Honestly it still runs great on that stuff, as in fastest time of the day fine, with the exception that it ATE the platinum Bosch Plugs, for the reason laid out buy Bob above. The ends of the electrodes sputtered right off. Swap to plain old Bosch copper plugs, no more issues.

Ashley James
356 Fan
Posts: 449
Joined: Sat Jun 04, 2016 2:38 pm
Location: Near Stroud, Gloucestershire, UK
Contact:

Re: Spark plugs

#28 Post by Ashley James »

I remember NGK plugs arriving in this country and life changing for ever. Champions were hopeless because they didn’t have a wide enough heat range. I holed several pistons in motorbikes because of them, but no problems with NGK and neither were there any with Lotus Cortina and others that were suffering from piling up or losing electrodes into the engine.

NGKs were sold by Stan Dibben who, along with Dennis Jenkinson had been World Champion Sidecar racer Eric Oliver’s passenger. Jenks also rode with Stirling Moss when he won the Mille Miglia in a 300SLR.

Then I got BMW motorbikes and they came with Bosch and gave no trouble.

Fred Winterburn
356 Fan
Posts: 106
Joined: Wed Sep 13, 2017 6:31 pm
Location: Ripley, Ontario, Canada
Contact:

Re: Spark plugs

#29 Post by Fred Winterburn »

Bob,
I've not signed onto the forum in a couple of weeks (trying to get the next batch of 6V units made which should be very soon--I will be sending emails shortly). If your car is running well, I would suggest run it some more and then pull the plugs and inspect them. If they look good, put them back in. There is only one type of platinum plug that concerns me with the CDI, and they may not even be made anymore. The type I am referring to were the early Bosch platinum plugs that had the centre electrode completely shrouded in ceramic right to the tip. My theory was that they wouldn't support the alternating current spark because the small surface area of the tip made the spark plug act somewhat like a diode (reference cat's whisker diodes for the theory). Since I always ran CDI, I assumed my theory was correct. It was my brother that told me they were poor performers on any car (he ran VW Eurovans for years). His theory was that the platinum sputtered away from inside the ceramic shrouding and was replaced with a layer of less conductive carbon. I really don't know the reason why those Bosch plugs were so bad, but they were. I'm sure that more modern versions that have more exposed area on the centre conductor perform as well as any other spark plug.
When I started designing this CDI, I tried various sized of discharge capacitors. My father's design used a 1.5µF capacitor most of the time, but on cars that typically had poor performing coils, (Bosch and Lucas) he upped the value to 2µF. I run 2.2µF. I found that if I went above 2.4µF, that metal would sputter off the electrodes on my test rig (which is the same old homemade test rig made by my father back in 1962). Anyway, spark plug erosion is actually less using this CDI than with the standard Kettering system. I tried experiments using two discharge capacitors and various other combinations and found that the simple design my father used actually worked the best. The only real difference that I have made to his design(s) is the power supply is better protected without any additional components and the spark duration is longer because the power supply can supply some extra oomph during the spark. Actually the hardest part was adhering to his design and making the unit universal for polarity. It is simple on paper but took me a couple of years thinking about it before I came up with the solution. I'm not as smart as the old man was! Fred

Fred Winterburn wrote:There are two types of spark plugs that I do not recommend for use with the CDI. The first is Champion resistor spark plugs. The resistors are weak (or used to be 25 years ago) and the CDI will make short work of them. The second spark plug that I don't recommend is the Bosch Platinum as shown in the picture. They are really poor with this CD ignition. My younger brother says that a high energy ignition will sputter off the platinum and leave a carbon core in its place. My theory as to why they don't work well with the CDI is the complete shrouding of the centre electrode except for the very tip. My theory is that the small surface area makes the spark plug behave like a rectifier which suppresses positive going sparks (this CDI spark alternates polarity a few times during each spark event). For whatever reason, that style of platinum plug does not work well.
I did not realize that my Volvo(B18B) and Morgan(TR3 engine) use the same spark plugs as the Porsche. If that is the case, the two plugs I use successfully with the CDI right now are NGK BPR6HIX on the Morgan, and NGK BZ7HS-10 on the Volvo. The latter plug is actually designed for outboard motors, is one heat range colder (OK with the CDI) and has an inductive rather than resistive suppressor to take the extra abuse of CD ignitions. Having written that, I have found that NGK resistors are robust enough to take the extra abuse this CDI can give (unlike the resistor in the Bosch rotor that will fail given time) Fred

Alan Hall wrote:I have never run platinum plugs but have seen a few and I believe the center electrode is solid platinum, not plated, but is a VERY small diameter wire held in the ceramic. See photo of a bosch W8AP platinum plug.

Post Reply