Your favorite spark plug gap?

[Virtuoso]

A couple years ago, I changed what appeared to be the original 11 year old, 195k mile plugs on our 2.4L Malibu. Two of the old ones were around .085 and the other two, .1 or more. New plugs were gapped somewhere around your typical .045 (stock). Car didn't seem to notice, ran the same.

 

[beast3300]

Originally Posted By: wirelessF
For the LM7 5.3L GM engine, newer spark plugs are now gapped at 0.044", not the 0.060" listed on the air filter box. I bought Denso LL's that came gapped @ 0.044".

I never seen a TSB on revised spark plug gaps for this engine but at the risk of damaging the iridium center, I never gapped it.


The TSB is for .040

 

[mechtech2]

I always gap spark plugs [except side electrode ones].
I like the high side of the recommended range.
If .048 to .052 is given, I'll use .052. A bigger spark is always better [until failure].
Factory specs are always on the safe side.
Some people stretch things .010 over or more with success. Everything else has to be perfect, though.

 

[hattaresguy]

Motors without them.

 

[PandaBear]

I've only seen 0.04-0.044 for distributor based system and 0.054 for waste spark system. You may be able to increase the gap further if switching to a fine wire plug but I'm not sure if it will buy you any advantage. In theory if you have a weak coil you can compensate that with a reduced gap, but why do that when the correct answer is to replace the coil?

 

[johnsmellsalot]

My favorite spark plug gap is whatever the owner's manual says.

 

[antiqueshell]

Originally Posted By: johnsmellsalot
My favorite spark plug gap is whatever the owner's manual says.


This is one specification where you should not question the manufacturer.

Even if you alter the gap and it "appears" that the car performs slightly better.....you could be creating other performance issues that will only surface over a longer period of time, including faster wear and tear on expensive critical components like ignition, emissions, and other items. Then when they fail much earlier than they should you will [censored] about it being poor quality. LOL

 

[mechtech2]

Panda and antique-

Gaps of up to .100" were used. They didn't work well, and were lessened to .080", and then about .060"

So experience and common sense show that the mfr. does not always know best.

 

[antiqueshell]

Originally Posted By: mechtech2
Panda and antique-

Gaps of up to .100" were used. They didn't work well, and were lessened to .080", and then about .060"

So experience and common sense show that the mfr. does not always know best.



Of course as with anything there are going to be some exceptions to the rule, but with modern vehicles (past 25 years?) I doubt that with critical emissions and other factors car companies are taking any chances.

It would be a incredible exception to the rule that a manufacturer would be incorrect about the proper spark plug gap today.