Sparkplug Advice 73 CIS 911

I have a '73 and a half 911T with CIS and I searched the 911 forum for info on spark plugs, and there wasn't a lot so I thought I'd get everyone's opinion. I just bought my car a few months ago and it had old splitfires in it that I did not care for. I replaced them with Bosch copper W5DC plugs from (Guess who) Pelican Parts. I just put in new injectors and had timing, dwell, injection, rotor, points, and cap done. But my mechanic suggested I get a hotter plug than the #5 Bosch. Could someone dispel the myths about hot or cold plugs, and the difference to me with a copper/silver/or platinum plug? My car is a daily driver and sometimes spends a week not even getting really warmed up. It has the stock 2.4 engine with 50K on the overhaul.

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Stephen Schafer 1973.5 911T targa

[This message has been edited by schaf (edited 07-25-2000).]

Well, those W5DC (or the Platinum W5DP replacement) Bosch plugs seem to be the 'standard' recommendation for your engine, and a NGK replacement is the BP7ES, with a slightly 'hotter' BP6ES also available, though I can find no recommendation for a hotter plug for your engine --- I think you should ask your mechanic WHY he is recommending a hotter plug than normally shown for your engine. You MAY need to find a new mechanic!!! Or, better yet, start to get familiar with your own car, and do your own maintenance!

My recomendation would be for you to check the condition of your sparkplug wires with an Ohmmeter or digital multimeter, end to end, individually. The resistance should be around 3000 Ohms, +/- 20 %. The actual resistance value is not critical, as long as it is a 'steady' value and not varying. If you find any of the leads open, then the resistor BERU connector has failed, and should be replaced. Your CDI ignition can 'jump' across the broken resistor in cold weather, but will develop a 'MISS' in hot weather, due to a slightly lower output spark voltage in 85 F or hotter weather.

If the black neoprene copper-cored wire is in bad shape I recommend replacement with AC-Delco brand 7 mm silicone bulk replacement wire called 'SS 550' available from most major parts stores carrying the AC-Delco brand. The ends of your OEM wires can be unscrewed from the original wire, a replacement piece cut to the same length, then the old ends can be installed onto the replacement wire. Personally, I do not like any sparkplug wire sets on our 911's other than stock OEM, claims made by other brands seem to be more hype than substance!

The air seals on the BERU connector are OEM VW part number 111.905.449 ... without the 'A' suffix! Generic replacements made in Mexico or Brazil can be found at most foreign car part stores. Those air seals are quite important, and when 'shriveled' ... should be replaced. Make SURE replacements you buy are not shriveled! I carry a dozen replacements, sealed in a Ziploc bag, in my tool kit at all times.

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Warren Hall
1973 911S Targa

[This message has been edited by Early_S_Man (edited 07-25-2000).]

Hi Warren,
The air seals ur talking are those round rubers that covers the spark plug holes in the valve covers. If so, mine are realy bad, and what problems can occur.
Sorry I lost my question mark on the keyboard.

Thanks for the info, but my original wires are the stainless steel braided/ shielded type and I was under the impression that was the recomended wire.

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Stephen Schafer 1973.5 911T targa

Hi, Marcello!

Yes, those seals are the ones that seat on the valve cover ... and I don't know precisely what leaks there result in, but it is just my 'gut' feeling that the engine needs 100% of the cooling air going where it was supposed to!

As far as the 'non-A suffix' version goes, you should be able to find them locally at a parts store not affiliated with VW ... I don't know about VW Brazil, but USA VW dealers stopped selling the 'old' version we need over 25 years ago! But, thankfully, Brazilian replacement parts have been available for our 'strong' air-cooled VW market here for many years ... and I ahd always assumed they would be available there locally for you, too.

Stephen,

Those shielded wires were for radio noise suppression, and had nothing to do with ignition requirements of the 911 engine, and since I have never had any noise problems on my Blaupunkt radio's ... I see no reason why you couldn't unscrew the indiviual ends, toss the inside neoprene wire AND the shielding, and replace the wire itself with new, bulk silicone wire. If you try running your engine in total darkness, check for arcing and 'CORONA' effects in your old wires. I suspect that they are putting on quite a light 'show' at night!!! Good luck!


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Warren Hall
1973 911S Targa

I think we might have it here. There are lots of old beetles running around.

Tks Warren...

Hey I just went outside and checked for fireworks... no lightshow, so that's a good sign... My neighbors love me...

BTW what 's the scoop on silver electrode plugs?

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Stephen Schafer 1973.5 911T targa

Check out these URL's for some sparkplug listings:
http://staging.huntinter.com/johncar/TipMFI.htm
http://staging.huntinter.com/johncar/New_Folder/bosch.doc

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Warren Hall
1973 911S Targa

Warren, I didn't see anything about silver plugs in those docs, does anyone have any experience with them? Didn't they come out after 1973? BTW I'll be checking the wires tonight with an ohmmeter since i do have a little miss at idle when the car is warm. Also perhaps you could explain the warm/cool plug thing to me so I sound like I know what I'm talking about when I talk to my mechanic.

Thanks -Schaf

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Stephen Schafer 1973.5 911T targa