4 Cam Spark plugs

Discussion of 4-Cam Type 547 engines (and all the Fuhrmann racing variants) and cars that powered them.
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Bill Sargent
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4 Cam Spark plugs

#1 Post by Bill Sargent »

What spark plugs are 587/1,2&3 owners running for street use?

I have been running Bosch silver W4CS and have occasional fouling even with twin CD boxes.
Regards,

Bill Sargent
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Harlan Halsey
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Re: 4 Cam Spark plugs

#2 Post by Harlan Halsey »

Bill,
I have no experience with 587 engines but 692 and 547 normally run retracted side gap plugs which have had a fouling problem since day 1. Faced with that issue in 1980 I solved it by running projected nose plugs. To make room I relieved the piston crown with a 1/2-inch ball end mill. I modify the projected nose plugs into side gap plugs to minimize the depth of the relief. I've never had a plug foul. A side benefit is that my plugs cost $3.00 each rather than $30.00 each.
Last edited by Harlan Halsey on Tue Apr 05, 2022 5:12 am, edited 2 times in total.

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Martin Benade
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Re: 4 Cam Spark plugs

#3 Post by Martin Benade »

A hotter plug doesn’t prevent fouling? Or will that cause detonation?
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Jeff Adams
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Re: 4 Cam Spark plugs

#4 Post by Jeff Adams »

The W4CS is what we run on all engines with pistons that clear the plug electrode. Are the plugs fouling with fuel or oil? Or both??

Olivier Auvray
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Re: 4 Cam Spark plugs

#5 Post by Olivier Auvray »

For engines with carburetors, I pulled out Bosch spark plugs from my shelves since many years! NGK is my Friend! Wider thermal range and higher fouling resistance!
You have more chance to see Vladimir Putin on a gay pride's float than to see a fouled NGK spark plug!

As I'm at home, I don't have my "secret book" with me so I can tell you right now the NGK reference.

Anyway, I think that it's easy to find the right number with a cross reference table.

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Harlan Halsey
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Re: 4 Cam Spark plugs

#6 Post by Harlan Halsey »

+1
NGKs in all my 356s.

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David Jones
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Re: 4 Cam Spark plugs

#7 Post by David Jones »

I just bought 2 x 4 packs of NGK BPR6HIX for $16 a pack, which was a deal I could not resist. Yes all my cars are wearing them.
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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Jeff Adams
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Re: 4 Cam Spark plugs

#8 Post by Jeff Adams »

I have not seen any difference in fouling resistance between NGK, Bosch, or any other brand in either four cam or pushrod engines. We stick with the W4CS for four cam and W6BC for pushrod and they work fine. Regardless of plug brand, fouling is usually an indication that something else is wrong. Oil burning from a worn engine, too rich fuel mixture, poor quality plug connectors with open circuits in the resistor, old solid core plug wires that cross fire, incorrect ignition coils, and so on.

One consistent problem related to plug fouling is resistor plugs. The currently supplied WR6BC plugs for pushrod engines are so awful that Bosch should be embarrassed supplying them. Whenever possible and given a choice we use non resistor plugs in all four cam, pushrod and early 911.

Olivier Auvray
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Re: 4 Cam Spark plugs

#9 Post by Olivier Auvray »

Jeff, I disagree, Bosch supplies low quality stuff or stuff near the lower side of the tolerance for vintage cars. On middle age (or older) engines, fouled plugs was, for me, a problem. I solved it with NGK plugs.
Close to the spark plug, I solved some others problems with NGK plugs cover:
antiparasite-ngk-droit.jpg
For 356 (including Carrera), this little boy, available from 1Kohm to 10 Kohm, is the best that i know.

Alan Klingen 2
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Re: 4 Cam Spark plugs

#10 Post by Alan Klingen 2 »

You might try going to NGK plugs I have had great sucess with them Alan The Stable.

Rainer Cooney
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Re: 4 Cam Spark plugs

#11 Post by Rainer Cooney »

I've been using NGK Iridium plugs for years now with no problems. The engines are set up with a custom crank fire ignition system that still uses the distributors for high tension along with new plug connectors and wires. The plugs, NGK Iridium BR8EIX, are certainly more costly but in relation to the value of a 4-cam engine and the car it goes in they seem a bargain. NGK claims more power (slightly) and better fuel economy but the real benefit comes in not having to change plugs in a Carrera with limited access and a hot engine. Spark plugs foul for a variety of reasons mainly centered around not being warm enough to self clean i.e engine start up or low speed running. Back in the day, if you had the money, your new Porsche racing car came with a factory trained mechanic to help with the running of the car. It was common place to start and warm up the car with plugs of a hotter heat range. Once warm the mechanic would then change to colder plugs that wouldn't eat holes in your crummy cast pistons.

Alan Klingen 2
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Re: 4 Cam Spark plugs

#12 Post by Alan Klingen 2 »

A "hotter plug can help with plug fouling but you can enter the "danger zone of putting a hole in a piston. You just have to balance all the factors and stay with the coolest plug that gets the results you desire. Alan The Stable Btw the best plugs I have found have been NGK Plugs. Alan The Stable.

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