Hotter spark plug recommendations for 914-4 (1.8 liter)?

[Windisch]

My '74 914-4 (1.8 liter) shows evidence on its plugs of running slightly richer than I would prefer (dark markings, with some slight sooty deposits...not completely combusted fuel?). The car has a twin, dual Weber set-up (40mm IDFs) and it hasn't been driven much on the highway recently (only warmed up and idling too much). Although I've been told that 914-4s don't like overly lean mixes, the current Bosch plugs it runs probably need to be exchanged for slightly hotter replacements. Any suggestions from the more experienced on this subject? [Once I have the new plugs installed, the car will probably be exercised once every two weeks for about 9 miles, just to keep it fresh.] Thanks.
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1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
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Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[raygreenwood]

[Windisch]

What kind of plugs am I running right now? Good question. When I pulled them to check, I failed to make a note of the brand and rating on them. I'll do that today. They are probably Bosch but I'll have to take a look.
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1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
----------------------
Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[Windisch]

By the way, my understanding is that NGK and Bosch have inverse heat-ranges ratings. That is, with NGK plugs, the higher the number, the lower the heat. With Bosch, the reverse is true (the lower the number, the hotter the plug). Isn't that strange?! Wonder why this seeming lack of standards uniformity exists?
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1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
----------------------
Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[[email protected]]

WR7DC and tune the engine and the carbs and you will be all set

[Windisch]

[Windisch]

OK. Pulled a plug and checked, only to find that the existing plug (with the obvious carbon debris) is a Bosch WR8CC + Russia -420 rated plug.

What's with the "Russia" tag on it?! Given that with Bosch plugs, a higher heat number indicates hotter (than a WR7, for example), what's with this? Does this tell me that my carbs are too richly jetted, perhaps?

Unless otherwise advised, I'll probably install the new set of Bosch WR7CD plugs (that are recommended specifically for a FI 914 1.8 liter engine) and check the main carb jets, opting for a slightly leaner jet...

"RUSSIA?!" Hummmph! Нет, спасибо, товарищ!
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1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
----------------------
Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[TornadoRed06]

[Windisch]

[raygreenwood]

[Windisch]

[Windisch]

I just checked further on Ray's advice about using a non-resistor plug (e.g. Bosch W7CC) instead of a WR7CD on an electronic-ignition equipped VW/914 and several on-line references, including one at PELICAN PARTS, affirm that advice. This was an important tech epiphany for someone like myself who is only a modestly skilled 'shade-tree' mechanic (despite years of SCCA SFO club racing work). I never gave much thought to the 'tech' details of 914 Groups C and E/F racing efforts, back in the 80s, leaving such considerations to the gear-head mechanics (duh!). But then, I've flitted back and fourth, over the years (to and from several marques) and now find my never-too-good memory getting worse and worse with age!

Next big subject for me to bone-up on will be appropriate Weber 40mm IDF carb main jetting, although I understand that a 130 main jet is probably a good starting point on a small displacement (1.8 liter) Porsche air-sucker. We'll see.
_________________
1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
----------------------
Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[Windisch]

FURTHER NEWS ON THE SPARK PLUG ISSUE:

SoCal (VW) Parts in Southern California sent me 8 RESISTOR plugs (WR7CD) instead of the 8 non-resistor (W7CC) plugs I ordered from them, despite SoCal advertising that the plugs were Bosch W7CC. When I queried them about this, their explanation was as follows: "We purchased a number of the Bosch W7CC plugs some years ago, but we've run out of that stock and now the plugs we sell are all Bosch WR7CD." They went on to say that both Bosch and Denso stopped manufacturing non-resistor plugs about 12 years ago.

They did not say whether that included Russian Bosch plug production, but it's anyone's guess, barring more precise and exact, up-to-date info on this matter.

All this is extremely confusing for anyone trying to figure out exactly what's-what here but I gather that RESISTOR plugs are now sanctioned as being fine for electronic ignitions and the NON-RESISTOR (Bosch and Nippon Denso) plugs are, if not available commonly, at least almost impossible to find presently. Or so say some of the aftermarket VW parts sellers.
_________________
1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
----------------------
Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[raygreenwood]

[Windisch]

Hi Ray and thanks, as always, for those shared insights. That seems like a good approach to take towards the plug issues. My coil is a Bosch 'Blue' and the disty is a Pertronix, so I guess good to go on those scores. Interesting to consider the nuances of disty/coil/plug combinations in detail...all aspects of ignition I haven't focused on previously, but definitely salient!

Now if I can just get a few good days of sun, higher temps and no freezing winter 'Tule Fog' to contend with (here in the 'Always sunny and never rains Californica' state), I can spend some quality time out in the garage with 'Jezibel', the yellow 914, LoL.

My 73 orange VW Bug hunkers down in the side driveway, outside, under its weatherproof cover but I can feel its vibes way out here: pure jealousy!
_________________
1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
----------------------
Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[raygreenwood]

[Windisch]

Copy that, Ray. Thanks.
_________________
1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
----------------------
Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]