Spark plugs

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Charles H Jacobus
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Spark plugs

#1 Post by Charles H Jacobus »

What's the best spark plug for a 1965C?

Thanks

Chuck
Current:
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1995 Midnight blue 993
1965 Red 356C

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

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John Lindstrom
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Re: Spark plugs

#2 Post by John Lindstrom »

NGK B6HF?

Dick Weiss
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Re: Spark plugs

#3 Post by Dick Weiss »

Or Bosch W6BC--Their Platinum WR7BP were discontinued several years ago, but any platinum will be OK and less fouling.

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Bruce Smith
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Re: Spark plugs

#4 Post by Bruce Smith »

See the link below, but the Bosch WR7BP+ (4032) is discontinued and has been replaced by Bosch WR7BC+ (7997)

https://porsche356registry.org/article/65
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Ron LaDow
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Re: Spark plugs

#5 Post by Ron LaDow »

Pt plugs were state of the art in the '50s. They were a solution to problems caused by the thermal instability of air-cooled chambers, allowing a "hot" plug design to fire the charge in a cold chamber and then rapidly pulling heat away from the electrode tip and therefore keeping the incoming charge from pre-igniting. Pt is hightly thermally-conductive and easily 'joined' to the corrosion-resistant electrode tip and the electrically-conductive stem. Worked, and Bosch (like the factory) has never been shy about passing on the costs.
'Bout that time, the Japanese started making air-cooled motorcycles they wanted to sell world-wide, which needed a solution for the same problem that didn't cost $10 every time you changed a plug and (I think) NGK came up with the technology to 'weld' Cu to the electrode, substituting a cheap, thermally-conductive alloy for the much more expensive Pt. Hey, presto! Poor yutes like me could afford a set of plugs for the iron!
I think several mfgrs still sell Pt plugs to those desiring bling, but since the late '60s, plain, old Cu-core NGKs have never let me (and millions of others) down.
And, Dick, I'm pretty sure the fouling was caused by the Pb in the fuel, not the plug design, but you could burn it off if you stuck a hot enough plug in there. The thermal conductivity of Pt (and now Cu) would help there.
Added by edit:
NGK plugs are hotter by the lower number: 6 is hotter than 7. Back when Pb was part of the fuel, the "P" series NGKs were helpful: BP6HS as opposed to B6HS. They are 'projected tip' (regardless of the thread length) and stuck the electrode out there in the chamber in the hopes of blowing the condensed Pb off the end. They mostly worked, but are no longer helpful, and if your engine is built for maximum CR, you might find the side electrode 'tapped' closed onto the center electrode, meaning that cylinder is not going to fire.
That phenomenon is not limited to recent engine builds; I found it with engines in cars I bought in the '80s.
Ron LaDow
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Charles H Jacobus
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Re: Spark plugs

#6 Post by Charles H Jacobus »

Thanks, guys!

Chuck
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) :)

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C J Murray
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Re: Spark plugs

#7 Post by C J Murray »

I had to find my periodic table to decipher Ron's post but he is basically correct except on one point. Extended tip plugs are an advantage in engines where there is room to use them. The farther into the chamber the spark is started the more reliable is the combustion and the faster the flame travels. An additional advantage is that the tip of the plug is held to a tighter temperature range and is less likely to suffer from overheating. This is true because the intake charge is more able to cool the tip between combustion events.

Like Ron, my engines generally do not have room for projected tip plugs but if your engine has room you should use projected tip plugs.
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Bill Oldham
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Re: Spark plugs

#8 Post by Bill Oldham »

A lot of practical knowledge here by the gurus like Ron and Cliff, but some confusion on the facts. For example Pt is not a good thermal conductor and would be way too expensive anyway as a solid electrode material. Plugs are coated with passive materials like Pt for their chemical properties, not thermal. I think spark plug technology made the huge progress (from 1-2K miles to >100K miles ) by heat flow design and chemical surface design (and elimination of Pb in the gas) in recent years. But the bottom line is that certain folks with lots of experience (liked those mentioned already) know what works in our little engines:

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Bruce Smith
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Re: Spark plugs

#9 Post by Bruce Smith »

I make no claims of the experience and expertise of others here but this is my understanding of the current Bosch spark plug technology. The + (Super Plus) in the Bosch WR7BC+ code is a yttrium enhanced copper center electrode together with a nickle plated ground electrode. Bosch has replaced their WR7BP platinum plugs with these. The yttrium is used to reduce erosion and oxidation. As an alloy, it a different approach than a Pt coating but can lead to similar advantages. As Bill points out, Pt plating is very expensive. A $3 Pt plug isn't going to have much of it and maybe only on the center electrode. Bosch claims the Super Plus (C+) plugs are as long life as the P versions.
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David Jones
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Re: Spark plugs

#10 Post by David Jones »

Many years ago I used the Champion L3G plug because it had a a very thin center electrode which at the time was supposed to promote a better spark propagation and it certainly seemed to work well but other reading at the time led me to believe that the difference between thread form was a downside that led to issues with seized plugs in VW heads used in racing so I switched to Bosch plugs. Since then my knowledge has improved and although it appears that the theory of the center electrode diameter still appears to hold true the issue with threads has gone away. I now favor NGK plugs and it appears they have a thin center electrode plug on the market which I think even though very expensive I may try in my new engine that I shall finish building this Winter.
This is the plug.
https://www.ngk.com/product.aspx?zpid=9488
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
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C J Murray
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Re: Spark plugs

#11 Post by C J Murray »

I apologize for posting this but it just had to be done. Get out the Tylenol.

https://www.vdlfuelsystems.com/anything ... ark-plugs/
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David Jones
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Re: Spark plugs

#12 Post by David Jones »

Spark plugs are just like fuel, CR and oil, one can debate forever and opinions will vary. I like multigrades and some prefer single weight.
What I really want is a multigrade version of Castrol "R" with no after effects except for the left over aroma.
If I had known I would live this long I would have pushed the envelope a little harder.
Cymru am byth
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Alan Hall
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Re: Spark plugs

#13 Post by Alan Hall »

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.
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C J Murray
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Re: Spark plugs

#14 Post by C J Murray »

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/
Note that the article was written by a Champion Spark Plug Motorsports engineer, a better source than the car magazines I would think.
'57 Speedster
'59 Sunroof
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'63 Cabriolet "Norm"
'67 911 S Original Owner
'03 Ferrari 575M
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Ron LaDow
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Re: Spark plugs

#15 Post by Ron LaDow »

Dogone it, Bill. Now I got to go looking for the source to see if they blew it or I 'interpreted' what was written.
Ron LaDow
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