280 SEL 4.5 Spark Plugs

[Litton]

I replaced my plugs a bit ago with Bosch platiniums but am starting to wonder if those are really the best plugs to use. I know from the 126 forum that platiniums cause problem in the 4.2 and 5.6 engines and I wonder it that is the case on the 4.5's. Looking at the plugs they seem to be really cold for around town driving. (lots of soot on the lower part of the nose, nice and grey near the tip)

With my new Pertronix ignition and coil, that the fouling issue with standard plugs should be a thing of the past.

What does the collective wisdom of the forum have to say on this topic.

[MikeTangas]

Dumps the Plats and get a set of W7DC's, copper core Bosch plugs. Your engine will be much happier.

[JMela]

On the 108 spark plug topic, I recently purchased a set of W7's gapped at .36. In order to achieve a gap of .28, I tapped the plugs against a table and regapped.

Is this considered poor form? My car's running fine but the idle is a little lumpier than it's been in the past.

Thanks - didn't mean to co-opt this thread...

[Litton]

Yep, I was thinking the dump also it will give me a chance to do what Pertonix recommends which is to bump the gap to .045 so as to take advantage of the "hot" coil....45,000 volts vs. 20,000 volts for the stock unit.

Bumping is recommended way to decrease gap. Great link.

http://www.boschusa.com/AutoParts/FAQs/SparkPlugs/

[Litton]

Official Spark Plug Adusting Tool

[psfred]

Platinums work fine so long as the resistance in the rest of the secondary ignition is correct. Stock has resistors in the rotor, wires, and wire ends (connectors for the spark plugs), so if you put in resistor plugs (all platinums are resistor plugs), you will get weak spark and running problems. If you replace the wire ends with the lower resistance ones, or replace the spark plug wires with non-resistor wires, you will be fine.

Your idle mixture is too rich, probably a bit rich on the main mix, too -- plugs these days are usually light tan rather than gray. Platinums are sometimes white with gray traces, though.

Black tips means its running rich just before you shut it off.

Tapping the side electrode is acceptable (bending with a tool is better), but if you every DROP a resistor core spark plug on a concrete floor, toss it out. The resistor core commonly cracks when you do that, and the plug won't every fire correctly again.

Peter

[Litton]

PETER, GREAT EXPLANTION!!!!

My plug tips are like #1 in the attached link. Light tan is about right,

http://www.boschusa.com/images/SparkPlugFaces.pdf

but only at the nose and maybe 1/4" down then it is sooty...wipes off easy like soot. One plug is light only at the very tip which make me think that plug or the associated wire is weak.

My cap is stock and the wires/end connectors are stock and seem to measure about 1.5 kohms of resitance for rotor nub to plug connector. So, if I understand what you are saying then the resistance plugs (like my plats) are not a good thing. Also, I know that I dropped a couple trying to get them in and I think the plug in question hit the deck twice. Plus, I had to regap them 'cause they always fall on there nose.

The car always sound like it has a slight miss but if I pull the injector wires each cylinder I lose about 50 rpm on all cylinders. (I don't pull spark plug wires anymore since I got knocked on my can)

[kpb]

Oh yeah, baby, I been there

[JMela]

Originally posted by Litton
[B]What Pertonix recommends which is to bump the gap to .045 so as to take advantage of the "hot" coil.

Hey Litton, I'm running one of those Pertronix coils as well, with stock .28 plug gap. What performance changes would I notice by bumping up to a .45 gap?

Thanks

[Litton]

Joe, according to Pertronix the higher voltage coil and larger gap will give increased performance, cleaner burning, better fuel economy, improved vitality, longer lasting, good weather, improved cash flow, etc, etc.

Seriously, newer vehicles all have large gaps out to .060 with modern electronic ignition so I believe some of the claims.

[psfred]

Wider gap should give better ignition under high resistance conditions due to the higher voltage from the coil, so start up should be easier and full load smoother. Usually give better performance and milage, but that is engine dependent. Hans said the used to open up the gap on the 250 (not the 230 or either 280) and get better low end performance and milage. Had the opposite effect on any other Benz for some reason.

The Pertronix coil is higher voltage than the stock Benz on for a 1972, so it will fire a larger gap reliably.

Peter

[yakerz]

I have a 72 108 4.5 . what is a petronix coil and does my car have one? also should i use the w7dc copper bosch plugs as well?

[kpb]

Pertronix is an aftermarket coil that many have installed. You should use the w7dc from all I have read.