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 » Mon Apr 04, 2022 12:32 am

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 » Mon Apr 04, 2022 4:23 am

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 » Mon Apr 04, 2022 8:32 am

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 » Mon Apr 04, 2022 10:47 pm

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 » Fri Apr 08, 2022 4:04 pm

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 » Sat Apr 09, 2022 6:21 am

+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 » Sat Apr 09, 2022 7:11 am

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 » Sat Apr 09, 2022 10:22 am

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 » Sat Apr 09, 2022 12:12 pm

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.

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