Spark Plug Gap

[RI Chevy]

I am just curious if anyone has ever experimented with the spark plug gap? Would going up a thousandth or 2 give better spark? Make for more power?
Or does everyone here just stick with the recommended .5mm gap?

 

[merc_man]

I normally dont check the gap. I probly should though.

Sent from my SM-J320W8 using Tapatalk

 

[RI Chevy]

Bump here! Has anyone ever adjusted the plug gap up or down a thousandth or two to see if you get any more or any less power?

 

[jakethesnake]

If the spark is there I don't touch them. Doubt you'd see any difference whatsoever

 

[RI Chevy]

That's kinda what I thought too. I just threw this out there to see if anyone had tried different plug gaps.

 

[jakethesnake]

I'm not certain. I just feel like as long as the fuel is being lit. It shouldn't matter. I honestly haven't tried and don't know the answer

 

[TJ the Chainsaw Mechanic]

In the automotive world More Gap means you need a hotter coil and better flowing plug wires to compensate. Typically with a points setup .035 is stock on most engines, but when an HEI is used you can gap Up to .045 to gain a little more spark. Hotter HEI's (50K coil or hotter) can use plugs with even More gap.... .050 to as much as .060. You have to have good low resistant wires though to make it even worth it. And still the results really aren't worth the money.

Funny thing is back in the 60's GMC used AC delco plugs in the 478 V6 truck engine that were Made to be gapped at .065! And that was with points! More spark for the big trucks because in a series 6000 big rig you were operating at wot a lot.

I am using those ac delco plugs in my 305 v6. They are gapped at .055 and I'm running a 45K pertronix unit. When I went from a .045 gap to a .055 gap the only thing I noticed was a little easier cold starting and slightly better throttle response. Power remained exactly the same...least by feel. May have gained about 5 hp. lol

I'll be running a hi perf davis unified ignition on my 292 I6 with super low resistant plug wires and NGK plugs. Will gap at .055. The moroso plug wires I will be running are 40 ohm's resistance per foot where as most are around 100 ohms per foot. We'll see!

Pretty much like most say....a Spark is a Spark.

I'd say try it for the fun of it and see, but you may actually Lose power from it as 2 strokes seem pretty picky on plugs being factory specced. Going through echo and stihl school I read that using the wrong heat rang or changing the gaps could actually take away top end rpm's.

 

[jb-chainsaws]

It's my limited understanding that with the same sized coil a larger gap will give a weaker spark and will also spark slightly later due to the increased electrical resistance of the extended gap. This may be only a couple of milliseconds but as I understand is still later.

Other more knowledgable folks may chime in and prove that I'm talking utter nonsense however, so take what I say with a pinch of salt

 

[RI Chevy]

Thanks guys. I appreciate the info. I guess I will just stay stock. [emoji106]

 

[Pincher]

On the farm, if a cylinder was misfiring on a four cylinder tractor engine we would pull the plug wire and make the spark jump a gap to the plug to bring the cylinder back. Was told the gap from wire to plug increased the power(voltage). As far as plugs making a HP difference, alcohol V8 engines on a dyno claim to find measurable HP gains by "indexing" the plugs.

 

[Al Smith]

I've used that old jump the gap trick for decades myself .

Some suggest to bend the electrode,sharpen it to a point and make a surface gap plug .They claim it works better which I have no idea if it does or not .

I've got a pair of giant plugs in the aircraft range of hot plugs I used on a John-Deere model A back when I took tractor pulling seriously .Damned things cost 18 bucks a pop back in the 80's .Old duffer had a Wico "roto fire" mag that put out a spark hot enough I swear it could start on kerosene .Weather those hot plugs made a diff I really don't know .It would however throw about a foot of fire out the stack if in a heavy pull .

 

[jb-chainsaws]

I've used that old jump the gap trick for decades myself .

Some suggest to bend the electrode,sharpen it to a point and make a surface gap plug .They claim it works better which I have no idea if it does or not .

I've got a pair of giant plugs in the aircraft range of hot plugs I used on a John-Deere model A back when I took tractor pulling seriously .Damned things cost 18 bucks a pop back in the 80's .Old duffer had a Wico "roto fire" mag that put out a spark hot enough I swear it could start on kerosene .Weather those hot plugs made a diff I really don't know .It would however throw about a foot of fire out the stack if in a heavy pull .

I'd love to see some photos of that!!

 

[Bobbyjr]

I've done quite a bit of this. The larger the gap,the hotter the spark. Also lighter plug color. The smaller the gap,the colder the spark,and darker in color.

 

[Homelite410]

I've done quite a bit of this. The larger the gap,the hotter the spark. Also lighter plug color. The smaller the gap,the colder the spark,and darker in color.

I like your theory, however wouldn't that make the coil work harder? On the automotive side, I have seen first hand, plugs that were ran too long (wide gap, iridium/platinum completely gone)and burned out the coils on 2 vehicles..

 

[Bobbyjr]

I like your theory, however wouldn't that make the coil work harder? On the automotive side, I have seen first hand, plugs that were ran too long (wide gap, iridium/platinum completely gone)and burned out the coils on 2 vehicles..

I suppose it would if the gap was very wide!? What very wide is,I don't know. I've never burned out a coil. This will work until a hotter plug is used.

 

[jake wells]

0.35 gap on everything.

 

[jb-chainsaws]

With regard to pressure and resistance, the spark gap that the coil can jump in air may not be suitable for some saws, and ported saws with bumped compression may struggle to spark at all as the gap and pressure both increase. I did some reading on this when building a hybrid potato cannon which used 4% propane and air compressed at 20 bar, and it got to the point where i had to reduce my spark gap for the TV fly back coil i was using to drive it. I assume this would be similar with saws reaching 200psi, as my coil was very similar to a saw coil in construction

 

[TJ the Chainsaw Mechanic]

I like your theory, however wouldn't that make the coil work harder? On the automotive side, I have seen first hand, plugs that were ran too long (wide gap, iridium/platinum completely gone)and burned out the coils on 2 vehicles..

It does put more load on the coil, therefore the need for a High Energy Ignition.

 

[Outback]

My sisters car blew a coil 5 years ago @ 130k, I pulled the plugs. .073/.075 gap..... original plugs. They last forever right?

 

[Chainganger]

On the farm, if a cylinder was misfiring on a four cylinder tractor engine we would pull the plug wire and make the spark jump a gap to the plug to bring the cylinder back. Was told the gap from wire to plug increased the power(voltage). As far as plugs making a HP difference, alcohol V8 engines on a dyno claim to find measurable HP gains by "indexing" the plugs.

I index the plug in a chainsaw with a gasket delete and tight squish so that the gap in the electrode faces down into the cylinder, less likely for the piston top to ram into the bottom of the electrode, maybe I am nuts, but that's what I do anyway. Should help with detonation too I would think.