Resistor wires and plugs used together

[1971 280SE]

Hello I am new to the forum..I was wondering if I could get some advice..I am currently using Beru 5000 ohm wires and Bosch resistor plugs..Some have told me that this is not a good combo..Would using resitor wires and plugs cause me to have less power or engine miss? I am running a pertronix ignitor and coil. I am having a miss at idle..Thanks for your help..

[LandYaghtLover]

It will not cause less power. Flame front is flame front. But some claim it can strain the ignition system and cause spark failure. Considering how cheap plugs are, it may be a good idea to get some non-resistor type and see if it clears up your miss.

[mercmad6.3]

Never use resistor plugs in Any Mercedes = simple answer
Use NGK BP6ES plugs. never use resistor plugs.(bosch plugs have suffered from bad quality in recent years)
Why not? the resistance is built into the ignition system to SLOW the actual spark. So instead of getting an instant flash,the spark becomes an Arc of current. If the mixture has been affected by any one of a myriad of causes, a quick flash will often Not ignite the fuel mixture .
BUT, if you have too much resistance as you have ,the amount of spark is diminished ,again causing power loss. Never ever use Carbon string leads for the same reason. mercedes use solid core copper leads with the 5kohm resistance built into the plug and distributor cap terminals. There is also a resistance built into the rotor so use only the best rotors and caps. Beru products are crap,to put it plainly. I have replaced dozens of them because the terminals inside and the rotor tip are burnt out . Often the cars fitted with them have covered less than 5000 miles before breaking down.

[1971 280SE]

I will put the NGK'S in... Thanks for your advice..

[Graham]

Originally Posted by LandYaghtLover

It will not cause less power. Flame front is flame front. But some claim it can strain the ignition system and cause spark failure. Considering how cheap plugs are, it may be a good idea to get some non-resistor type and see if it clears up your miss.

Both NGK and Bosch say that there is no reason not to use resistor plugs even with the 5K wires. In fact they recommend their resistor plugs and even provided backup technical data (which you can find elsewhere on this forum) to illustrate how little the effect of adding 5kohm of resistance is when you have a ~25KV potential across the ignition path.

But as someone already said - no reason for us not to experiment and use whatever we find or feel works best.

For a small miss, maybe make sure the cap and rotor "contacts" are clean and that the cap is properly seated. Clean injectors and properly set idle and load mixtures may also help.

[Adv_rider]

Originally Posted by mercmad6.3

Never use resistor plugs in Any Mercedes = simple answer
Use NGK BP6ES plugs. never use resistor plugs.(bosch plugs have suffered from bad quality in recent years)
Why not? the resistance is built into the ignition system to SLOW the actual spark. So instead of getting an instant flash,the spark becomes an Arc of current. If the mixture has been affected by any one of a myriad of causes, a quick flash will often Not ignite the fuel mixture .
BUT, if you have too much resistance as you have ,the amount of spark is diminished ,again causing power loss. Never ever use Carbon string leads for the same reason. mercedes use solid core copper leads with the 5kohm resistance built into the plug and distributor cap terminals. There is also a resistance built into the rotor so use only the best rotors and caps. Beru products are crap,to put it plainly. I have replaced dozens of them because the terminals inside and the rotor tip are burnt out . Often the cars fitted with them have covered less than 5000 miles before breaking down.

Which brand and model are these?

[Pooka]

You might pull the plug wires from the distributor cap and see if there is any blue powder down in the holes in the cap. This would indicate arcing of the wires from not being seated correctly and this will cause a slight miss.

[Tomguy]

Originally Posted by Adv_rider

Which brand and model are these?

Factory. The boots have the resistances stamped on them. The aftermarket Bosch replacements do not, they use carbon core wires, IIRC.

[Graham]

Originally Posted by Tomguy

Factory. The boots have the resistances stamped on them. The aftermarket Bosch replacements do not, they use carbon core wires, IIRC.

Sorry, but that is likely not right. The Bosch wires for v-8 engines are copper cored and I posted a reply received direct from Bosch, confirming this, in another thread.

The wires themselves ARE marked: "Bosch 7 mm opti-layer copper core ultra premium"

Maybe for the M130, the wires are different, but I doubt very much they are carbon.

[1971 280SE]

Hello all, I was looking in the Haynes manual and they specify a bigger gap for resistor plugs..They have the gap for non resitor plugs at 0.28-0.32 and the gap for resitor plugs at 0.35-0.39...Am I wrong in assuming that the increaaed gap would create more resistance..A layman would look at that and think it would be the other way around...There seems to be a lot of controversy with the resistor plugs..I may just put the Ngk's in there..On another note does anyone have any recommendations for the optimal ignition timing setting? A lot of people have told me that the M130 does not really like the factory recommendations..

[Tomguy]

Originally Posted by Graham

Sorry, but that is likely not right. The Bosch wires for v-8 engines are copper cored and I posted a reply received direct from Bosch, confirming this, in another thread.

The wires themselves ARE marked: "Bosch 7 mm opti-layer copper core ultra premium"

This is good info. Because a few years ago that wasn't the case, and it was the main reason I re-used my old ends just with new wire between them.