So I was told that the Coil that sits on the plug fires the cylinders primary spark plug, while the cross over wire from that coil fires off on the down stroke of a cylinder on the other side of the engine to clean it up for emissions.

Since I'm on a tight budget I only changed the 8 plugs under the coil packs since they are the primary plugs that fire. I figured the plugs that clean the cylinders emissions don't need to be perfect so I left them as is.

Anyone else agree that it might be a good idea to save a bit a cash & only replace the primary plug and change the others every other plug change? Not worried about emissions!

 

You aren't saving much when you compare it to possible engine rebuild or cylinders misfiring. You can get all 16 plugs for 30 bucks. It's not expensive.

 

You might check out rockauto.com, they have oem replacement plugs for under $3.00
You may have to change them every 30K but its better than undesirable engine performance.

 

I paid $28 for plugs on the Ram and $26 for plugs on the 300C. If I'd done only eight, I'd have saved a whopping $27 on both vehicles. Not worth short-changing the motors.

 

Whenever I've changed my plugs...... Both sets were equally worn.
I'd rather have piece of mind IMHO.
Al.

 

Of course they would, because both sets fire, but only ONE at a time unless you do the short wire hookup & delete the cross over method

The plugs do not fire at the same time in each cylinder, one at a time does. The 2nd plug gets fired on the down stroke of each revolution to clean up the chamber of emissions...even a weak plug could do this job, has nothing to do with power, just makes the hemi capable of burning all the un burnt gas & passing your emissions test. In fact nobody anywhere has any dyno numbers or has any proof that either doubling the spark via short wires & deleting the cross over method or simply running on 8 plugs has any major effect on performance or drivability, its a mixed bag...though I suspect/assume not using both plugs at the same time may eventually have an effect on emissions and throw a code for efficiency, though a worn plug for the down stroke won't be a noticeable effect on the engine running because it only burns up unburnt fuel left over from previous combustion.

As for grenading the engine, its very doubtful. In theory and on paper more fuel in the chamber the less chance of damaging pre detonation, so changing just the plugs that actually do the business end of firing & making the cylinder move won't make your engine grenade.

What will make a 5.7 liter Hemi Grenade? Water getting sucked into the cylinders via the notorious intake gaskets that go bad!.

 

Still don't wanna have multiple misfire codes being generated on the second plug when worn out.
I didn't mention at all that the second plug generates more power.
You did.
I know it's for emissions.
But hey...... $3 a pop for another 8 plugs doesn't phase me.
I have piece of mind that the centre porcelain and electrode won't drop out of the plug and screw my cylinder lining or top ring landing

 

I did not say that it gave more power... I said theres no dyno chart proof that in the configuration of our 5.7 Hemi's it makes a difference in having that second plug firing at the same time with short wires and no cross over or firing on the down stroke. Nobody has provided anything in that configuration to say the effects of it. Plugs falling apart within 70,000 miles? My ex girl friend put 150,000 on her car and never changed the plugs...what kind of cheap @$$ plugs would fall apart like that & fall into the cylinder?

 

You'd be surprised what type of plugs do fail. Issue have been posted on here from memory.
Anywho..... I will be changing all my plugs as I say, for that piece of mind.
Worth the $3 or so for the 8 plugs = $24 to me and a bitf extra of my time.

 

I sell them for $1.99 a piece at O'Reilly's.