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Post Info TOPIC: Mercedes Benz 420 and 560 V8 Tune Up - SPARK PLUG thread M117/M116
What is the Best Spark Plug for 1986-1991 V8 Mercedes? [11 vote(s)]

BOSCH Non-Resistor W9DCO (No Longer Avaliable)
27.3%
NGK BP5EY V-Power
0.0%
BOSCH SUPER 7607 w/ V-Profile Low Resistance Yugoslavian @.035 420 and 560
36.4%
BOSCH SUPER PLUS 7905 w/ V-Profile @.032 420 M116
0.0%
BOSCH SUPER PLUS 7911 w/ V-Profile @.032 560 M117
18.2%
CHAMPION - Part #302 (n11yc) - Non Resistor
9.1%
MERCEDES BENZ Part # 003 159 10 03 - Non Resistor
9.1%
OTHER
0.0%


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Mercedes Benz 420 and 560 V8 Tune Up - SPARK PLUG thread M117/M116
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We gave the NGK Split fire a day in court here at Stellar Enterprise and have found them to be lacking. The part number that many at the local parts stores will give you is-

BPR5EY
or
1233 (Stock Number)

Here is what they look like.







If you look at this last photo you can see the very top of the plug. This part will not come off and should you install these plugs in your Mercedes using traditional wires they will not accept the plug wire. These plugs have no business being listed for a Mercedes Benz.

They also feel very cheap. Holding a Bosch Super in one and and a NGK in the other and you will soon realize which one come from Japan. In my opinion the NGK plus are junk and should be left for the ricers.

Anyone else have any spark plug stories they want to share?


Edit by Administrator 3/21/2008- Click on the link below for tune up procedure

ALL NEW TUNE UP INSTRUCTIONS FOR 420 AND 560 V8 ENGINES





-- Edited by SELLC on Friday 24th of April 2015 12:33:41 AM

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Rookie

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RE: STAY FAR AWAY FROM NGK PLUGS!
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The problem you are having with the NGKs is that you are using resistor plugs. Try the BP5EY 7327 plugs. Your wires are resistor wires. Those coupled with resistor plugs will give unsatisfactory performance. Get the BP5EY 7327 plugs. Make sure there is not a R in the part#. The R designates it is a resistor plug. Hope this helps.

Pete

-- Edited by allnpt0 at 18:47, 2007-08-18

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83 380SEC


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allnpt0 wrote:

The problem you are having with the NGKs is that you are using resistor plugs. Try the BP5EY 7327 plugs. Your wires are resistor wires. Those coupled with resistor plugs will give unsatisfactory performance. Get the BP5EY 7327 plugs. Make sure there is not a R in the part#. The R designates it is a resistor plug. Hope this helps.

Pete

-- Edited by allnpt0 at 18:47, 2007-08-18



If you dont mind me asking, what year and model Mercedes are you working with?

I guess what really bugs me about NGK is the fact that they list the BPR5EY or 1233 as a usable part number for the Mercedes Benz 560 when in fact there is absolutely no way the BPR5EY/1233 will work. Since the tops of the plugs will not unscrew they can not be used with OEM wires. For this reason NGK leaves a bad taste in my mouth.

I plan on ordering in quite a few different kinds of plugs such as the Bosch, Bosch Super and I will also order up a set of the BP5EY 7327.  

Another spark plug that I DO-NOT recommend for the Mercedes, (Or any other car for that matter) is the Bosch Platinum line. Have a look at the photos below and you can see how small the electrode is. The electrode is so small that it does not take much to foul these plugs out. I myself would stay away from these plugs-

Bosch Platinum (Inferior electrode design)
NGK BPR5EY / 1233

Thanks for the part number allnpt0; will these plugs BP5EY / 7327 fit the 89-91 MB 560? If so we will give them a shot and report back. How have they been treating you? I only ask because your signature says 1983 380 SEC. For some reason I have been most impressed with both the regular Bosch and Bosch Super "Copper" core non-resistor plugs. Just call me old fashioned.

-- Edited by Stellar007 at 11:26, 2007-08-19

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RE: Mercedes Benz V8 117/116 Tune Up - Spark Plug thread
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At this time (11/1/2007) it appears that the spark plug offered by BOSCH as a replacement plug for most all US production 1986-1991 Mercedes-Benz 420 and 560 SEL is-

1986-1991 Mercedes-Benz 420 V8 M116 Engines-
BOSCH SUPER SPARK PLUG #7905 @ .032 gap O.E.

1986-1991 Mercedes-Benz 560 V8 M117 Engines-
BOSCH SUPER SPARK PLUG #7911 @ .032 gap O.E.

We have found that the lowest resistance and most stable plug can be had with a BOSCH SUPER PLUS 7607 however it is listed as a Yugoslavian plug WR9DC. These low resistance high output plugs will come pre-gapped at .023 however they will need to be opened up to .035 in order to get the best idle and performance. These plugs measured at a STABLE 4.8k ohms resistance.

BOSCH - 7607 4.8K Ohm Stable performance alternative



Proper gap is .035 thousandths.

As you can see all the BOSCH SUPER PLUS spark plugs also incorporate the V-profile on the ground terminal. These plugs ARE resistor plugs @ a stable 4.8 ohms tested resistance. The reason for this is to PROTECT the ignition system and other sensitive circuits from interference frequencies. Many people from the forum BenzWorld.org are mis-informed and spreading FALSE INFORMATION. Mercedes-Benz incorporated resisters into ALL of their wires from the factory; therefore the need to suppress interference was accepted and adopted by Mercedes themselves. See our write up on Resistor Plugs right here in the W126 forum on BenzWorld.US. What ever plug you decide to run with be sure the gap is set between .032-.035 for the best idle quality and performance.

-- Edited by Stellar007 at 08:04, 2007-11-11

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RE: Mercedes Benz 420 and 560 V8 Tune Up - SPARK PLUG thread M117/M116
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Anyone who says that resistor plugs are bad for Mercedes is talking out their ass!

Read this here-
Resistor Spark Plug MYTH
Mercedes-Benz 420 and 560 MAJOR TUNE UP THREAD

While it is true Mercedes did not put a resistor in the original equipment spark plug W9DCO they did in fact put resistors in the spark plug wires that would give about 1.5-1.8k on upwards of 7k Ohm's of resistance to help suppress frequency disturbances on electrical equipment such as your ignitions magnetic pickup, stereo and other sensitive electrical equipment.

Now days they are also implementing an additional 4.8k ohm's on thru 7 ohm's worth of resistance (Depending on the plug) within the spark plug for a total of 6.2k - 10k Ohm's resistance total between both plugs and wires (Depending on plug and wire). New stock BOSCH wires have a resistance of 1.5k Ohm where as some other manufactures such as Bremi and Beru are upwards of 6-7K Ohm's worth of resistance in the wires ALONE!  To say that this extra 4.8k Ohm of resistance will equate to any significant loss of power, performance or reliability is sure ignorance! We tested them back to back with NO change in seat of the pants performance. Then again we were using our kit with the low resistance 7607 Bosch Supers. This kit will give you the LOWEST possible resistance yet still maintain a clean noise free operation that will not cause stereo whine or other electromagnetic interference.

We have also found that the new BOSCH SUPER PLUS has a better design than that of the NGK BP5EY in that the BOSCH SUPER PLUS spark plugs have the V power built into the ground electrode rather than taking away from the surface of the electrode like NGK does. I think if the people on BenzWorld.org would just start setting their spark plug gaps at .035 instead of telling people to set them at .045 they would not be having problems. The factory recommends a gap of .032-.035 and that is what they need to be set at.

Just thought I would let you guys know the truth and on the other hand if you are building a race car and do not care about alternator whine or interference you could honestly have a case for going with resistor less plugs, however if you dont fabricate resistor less wires then its rather pointless anyway now isnt it?

  I found this photo while lurking about on the internet. This photo is a cut-away of a Beru sparkplug wire rumored to have upwards of 6k ohms resistance! That is some 4.5k ohms more than a BOSCH spark plug lead and even 2k ohms more than the Bosch spark plug wire resistor and resistor plug #7607 together!

NON-OEM BERU Spark Plug Wire measured @ +6.5k Ohm's



I myself personally have found the BOSCH items to be of best value, resistance and longevity. The wire sets sold by BOSCH have a lifetime warranty offered thru the manufacture.


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WE NOW HAVE THE STEP BY STEP PROCESS FINISHED FOR PERFORMING A TUNE UP ON 1986-1991 MERCEDES BENZ 420 AND 560 ENGINES

INCLUDED IS THE FIRING ORDER AND ALSO DETAILED PHOTOS!

ENJOY!!


ALL NEW TUNE UP INSTRUCTIONS w/ FIRING ORDER AND PHOTOS


firingorder126.JPG

-- Edited by Administrator at 08:12, 2008-03-21

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I wanted to post up some details about the distributor cap removal.

Sometimes after a cap has been on there awhile the bolts like to sieze up and cause the phillips head to strip out. I am seeing this more and more as they come in for service.

The best way to go about taking care of this problem is getting a large drill bit and drilling off the head of the bolt. Just drill until the head is completly gone and the cap comes right off leaving a stud. From there get some vise grips and "GENTLY" work the stud back and foruth ever so slightly until it works loose. Take your time and "Work it". This will be a lot less of a pain that having to drill and re-tap the hole. In worse case situations I have seen people drill straight thru with a nut on the under side of the distributor. Using this method can avoid that.

I have included photos and I am re-opening this thread also.



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I have found a resistor-less spark plug that seems to work well and is fairly inexpensive.

The Champion Spark Plug part number 302 (n11yc) seems to be performing well for me after having to perform a tune up on my personal 560 SEL. I had originally sought to purchase some Mercedes 003 159 10 03 OEM plugs but none were in stock at the time.

So, if you find yourself unable to obtain OE plugs, I have found the Champion n11yc (PN 302) to be quite nice in a pinch. Nice and heavy plug, and better than the NGK's that opened up to almost .070 gap due to wear. Gap the new plugs @ .032-.035 and check them the next time you perform a tune up. 

 

 



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State of Michigan Certified Master Auto Mechanic +2

Specialty Certified Since 1994

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