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sharknose View Drop Down
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Direct Link To This Post Topic: Fan shroud and Spark plug questions
    Posted: 14-December-2004 at 13:52

Couple of questions....

Any suggestions for dealing with the pesky fan shroud? Specifically I'm talking about removing and refitting it to allow access to the disi cap etc. So far I unscrew it at the top, and then struggle to move it out of the way, and generally it seems to get jammed/stuck and cause me loads of grief - there must be an easier way I'm sure.

Also, where can I get some "proper" plugs for my 635? Bosch WR9LS I believe - everywhere I've tried seems to try and sell me Platinum Super 4's instead. Even the GSF and Eurocarparts websites don't seem to have them.



Edited by sharknose
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Direct Link To This Post Posted: 14-December-2004 at 14:29
I've used "Super 4" type before without much of a problem. Currently I'm on the ordinary Bosch single-electrodes, but will change back to "Super 4" at next oil change.....

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Direct Link To This Post Posted: 14-December-2004 at 19:06
do those super 4's do what it "says on the tin"?
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Direct Link To This Post Posted: 15-December-2004 at 15:29

Platinum Super 4s good? Not always; some cars don't like them as they have a resistor in (I believe). Standard 6er plugs are non-resistor plugs, and although many people will try and tell you it won't make a difference if you have a resistor in the plug or not, it simply ain't so.

If you have a Euro-spec 6er you should be grateful no-one has sold you a set of WR9LS plugs. These are completely the wrong plugs for your car. The WR9LS may be a good idea for a low-compression US spec car. They are not recommended for Euro 6ers as they are the wrong heat range, they have the wrong reach, and they have a resistor in them. If you drive the car hard you will overheat these plugs and probably hole a piston or something nasty like that. The 'S' means they have silver electrodes; these are really only of any benefit under low-speed running conditions. The 'L' means they have a far-extended centre electrode, which means that your pistons might hit the ground electrode which sticks out about 3mm further with these plugs than the correct type.

The correct plug for a typical UK 6er (running leaded fuel) is a Bosch W8DC or equivalent. If using unleaded fuel a slightly colder plug isn't a bad idea, so going to a W7DC won't hurt.

If you want a more long-lived plug, consider a Bosch W7DTC, or an NGK BP6ET. These are a good fit and heat rating for a typical 6er, and they have triple ground electrodes, so last ages. With unleaded fuel, then unless you are burning a lot of oil, figure on 20000 miles or more out of these plugs. These are a standard VW plug fitment, so you can buy them pretty much anywhere. 

You can usually set the plug gaps to 0.8 or 0.9mm if you are running unleaded fuel; they won't wear too badly and the spark will  be a bit better for it. However if your ignition system is a bit flakey it might protest.

Please post with the model, year, and specification of your 6er if you would like more details.

BTW if you want to access the dizzy cap better, you could move the whole radiator out of the way. Alternatively try jacking up the engine slightly and loosening the RHS engine mounting. 

HTH.

cheers

 


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Direct Link To This Post Posted: 17-December-2004 at 13:17
Fabulous info - useful stuff

Anyone able to advise in the same way about plugs for the M6??
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Direct Link To This Post Posted: 18-December-2004 at 07:32
Originally posted by monkeyboy6059 monkeyboy6059 wrote:

do those super 4's do what it "says on the tin"?


The ones I've got are not the infamous WR9LS. They are definitely marked WR78....

WR78? Available in packs of 4 at most local Halfords or in any quantity at your local motor factors, e.g. Automarket in Barnet, Herts is my preferred resource.

Oddly enough, when new there was a reluctance to start from cold. Having said that, I used them in my original cylinder head (which I later discovered had a crack) with the original blue-coloured HT leads which were VERY old. After a few hundred miles, however, they were much like any other plug. My BMW mechanic says they're nowhere near worn out and can be re-used.

So, I am putting these WR78s back - 1-year-old cyl. head, 1-year-old HT leads now - after taking the current single-electrode ones out (these have been doing duty for the past year).

I will now have to see whether the rate at which 4-star is burnt improves by, ooh, 0.2mpg or so....!

Edited by Horsetan

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Direct Link To This Post Posted: 18-December-2004 at 07:34
Originally posted by Brucey Brucey wrote:

...consider a Bosch W7DTC....they have triple ground electrodes, so last ages. With unleaded fuel, then unless you are burning a lot of oil, figure on 20000 miles or more out of these plugs. These are a standard VW plug fitment, so you can buy them pretty much anywhere.... 



We've used them in our family VWs for years. These triple-electrode ones are very tough.

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Direct Link To This Post Posted: 18-December-2004 at 16:52

This is a section from an article I am writing on spark plugs at the moment, It relates to M635 spark plugs:

The standard plug is a Champion A6G, or an NGK D8EA. These have a 12mm thread, 19mm reach, a flat seat, a detachable SAE ferrule, 17.5mm or 18mm hexagon, standard nose projection, no resistor, and are relatively hard (cold) plugs. The standard plug gap is 0.6mm. The Champion plug also has a precious metal centre electrode, whereas the NGK fitment does not. This is why the NGK plug costs about 1/3 the cost of the Champion. If you have difficulty in obtaining the correct plug, go down to your nearest motorcycle dealer if you want the NGKs- they will almost certainly have them in stock. They may not even be surprised if you want six of them at once; they are one of the plugs that are used on the infamous six-cylinder Honda CBX 1000.

 

 I’m not sure there is a recommended Bosch fitment for this engine, but the Bosch X4CS is a close match for the NGK D8EA in some applications. Some versions of the BMW M3 uses Bosch X5DTC triple ground plugs. However, the X5DTC will have a longer nose projection than the standard M635 NGK or Champion plug, so it may not fit the M635 without piston/plug clearance issues. Also, the Bosch 5 grade is a little hotter than the standard M635 fitment. There does not seem to be an X4DTC plug made.

 

 NGK D9EA is a colder version of the standard D8EA plug, maybe good for a track day. NGK DR8EA-L is a half-heat grade harder than standard so lies between the two (although it does have a resistor). NGK D10EA is colder again, and although these plugs exist and are a standard fitment on at least one MotoGuzzi motorcycle I don’t think they are so easy to obtain in the UK. NGK D8EV is almost identical to the Champion A6G fitment with a precious metal electrode, or there is the D8EVX with a booster gap. Both are also available in a ‘9’ heat range. Several NGK ‘V’ plugs are now obsolete, and all may become so in time as NGK are concentrating more on their iridium series.

 

 There are also Nippon Denso, Autolite, Motorcraft, AC Delco and Splitfire plugs that will physically fit (asides from the projected electrode query in some cases) and have about the right heat range. However, I don’t have any experience of these plugs, or how consistent their heat ratings are; I would therefore consult the manufacturers to see if they are a recommended fitment before using any of them.

 

 It should also be noted that the M635/M6 went into different markets in various different states of tune, so it might not be wise to (say) fit a US-made plug that is meant for a US-spec M6 (typically less than 250bhp, with a catalyst fitted) to a full Monty 290bhp UK-spec M635 and then go thrashing round a track. It would be asking for trouble, as the heat range might be a bit hotter on such plugs.

 

 Outside of the above, the choice is limited. DR8EIX, DR9EIX are the newer NGK Iridium plugs, but these have a resistor in them (as do the Nippon Denso Iridiums) which may not be an altogether good thing. There are NGK racing series plugs that might also work, and if the engine is in a highly tuned state (so that a D9EA or a D10EA won’t do) these may be the only option. They definitely won’t be cheap though.

 

 It may be that a projected electrode plug can be used in the M635 engine. To determine this, an accurate clearance check would have to be carried out. If so, DP8EA, DP9EA, and Bosch X4DC become possibilities, as do DCPR8EKC, DCPR8EKP. Although the latter have a 5/8in. hexagon and a resistor, they are some of the few plugs in this fitting that have and appropriate heat range and multiple ground electrodes.

 


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Direct Link To This Post Posted: 20-December-2004 at 15:27

On the subject of spark plugs, anyone ever had this happen?

Changed my spark plugs last week, on number 2, as I was tightening it and it began to load up, the wrench suddenly 'gave' and then just span round and round.

Strange I thought, so removed the wrench, and out came the plug. Actually, strictly speaking, part of the plug came out - the body and the electrode, with the threaded section sheared off and still sitting screwed into the block.

Obviously, at this point, my eyes went somewhat wide, with thoughts of having to have the block machined, etc, etc.

Fortunately, I managed to use a tap wrench fitted with a left-handed thread to remove the remaining section of the plug, so all was well.

Still wondering what caused it to happen though - dodgy plug (manufacturing flaw?) I'm hoping, as I didn't over torque the plug - granted I wasn't using a torque wrench but it had barely started to load up when it went. 

 

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Direct Link To This Post Posted: 20-December-2004 at 18:32
Originally posted by sharknose sharknose wrote:

On the subject of spark plugs, anyone ever had this happen?



Nope.

Not yet!

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Direct Link To This Post Posted: 21-December-2004 at 14:03

What brand and model of plug, and where purchased?

What torque at failure? We need to know!

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Direct Link To This Post Posted: 21-December-2004 at 15:01

Well, they were Champion plugs, (exact model I can't remember). Got them from the local motor factors, who cross-referenced them in the relevant book.

Like I said, I didn't actually use a torque wrench, but I am 101% sure that I didn't overtorque them, the plug began to go tight, then as soon as I put any weight on it, sheared off.

It has made me wonder about using those plugs. The car runs fine on them (way better in fact since I changed them) but this incident has made me think twice, I may well get the "proper" Bosch plugs for the 20 or so quid it would cost.

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Direct Link To This Post Posted: 06-January-2005 at 18:51
Originally posted by Horsetan Horsetan wrote:

....I am putting these WR78s back - 1-year-old cyl. head, 1-year-old HT leads now - after taking the current single-electrode ones out (these have been doing duty for the past year).

I will now have to see whether the rate at which 4-star is burnt improves by, ooh, 0.2mpg or so....!


The WR78s are now back in place. The fuel consumption comparisons with the traditional single-electrode plugs will shortly be underway.

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