JUNKYARD LS PLUG GAP TEST. DOES MORE GAP EQUAL MORE POWER? HOW MUCH SHOULD I RUN? .010 VS .100 GAP

DOES GREATER PLUG GAP PRODUCE POWER? HOW MUCH PLUG GAP SHOULD I RUN? CAN I ADD PLUG GAP TO ADD POWER? WILL LESS PLUG LOWER POWER? IS A CHANGE IN PLUG GAP WORTH ANY POWER? CHECK OUT THIS TEST WHERE I RAN A NATURALLY ASPIRATED 5.3L WITH A BTR RED HOT CAM. I MADE DYNO PULLS WITH THE PLUG GAP SET AS LOW AS .010 (TEN THOU) TO AS HIGH AS .100 (100 THOU). DID THE POWER CHANGE AT ALL? IS CHANGING THE PLUG GAP WORTH ANYTHING? CHECK OUT ALL THE RESULTS.

[BensMiniToons]

My dad was a Machinic for 60+ years. He would always use a screwdriver to add about about .050 gap on something if it was having ignition issues saying it would give it a better flame.. As a by the book person wondered about it how it effected things. He was the best in town for a reason. RIP Dad.

[wesalker]

Back in my "dealership days" I remember increasing spark gap by .010" to .045" eliminated a multitude of drivability issues. The zone rep said I was crazy, until he had the opportunity to try it himself on his company demo. I should also mention that this "fix" was only needed on GM 5.0 liter engines. At the time, I was working at an Oldsmobile dealership. A few months later, they issued a service bulletin. I was the source of several service bulletins, back in the day.

[markgarland]

When I experimented with plug gap, I I never went as drastic. But the difference wasn’t in horsepower or dragstrip numbers. What we noticed was a little better driveability with a slightly larger plug gap.
We got the idea because of the driveability improvements from swapping a points type distributor (with.035 gap) to an HEI (with.045 gap). I recognize that the hotter ignition factored in, but several people felt that cars felt smoother and slightly torquier around town with a little extra plug gap.
It’s worth noting that we did this on engines with a distributor and a single coil. I believe that the individual coil system is so hot and the ignition coil recharge time is so quick that it is already incredibly efficient. I think your test confirmed this.

[Diveto]

If you increas the gap the spark will be longer = burning more fuel in the cylinder = more power and efficiency
But if the spark didn't reach the point
You will get miss fire, all depends how powerful the coil is, powerful coils = longer sparks

[engenhokas]

Moist (fuel) air, temperature and pressure all that dictates how much voltage you need to jump that gap. Bigger gap takes longer to build up, in some cases ignition adjustment is advised.
On 2 strokes if you bog down at mid-rpm, CLOSING the gap will actually help you to get into the powerband.
On a 4 stroke i ran into cars who likes the plugs a bit more closed than factory (perhaps worn coils couldn't build as much voltage)
Some others had some missfire issues and making the gap a bit bigger helped to fix that issue. Gap too open you get missfire again, there's a gap you can finetune your engine to, but every engine has it's own. Best is to try and find out what's best for you. The spark plug that works perfect in your engine, can be the sparkplug that makes my engine missfire all the time X)
Have a great day

[herseem]

You've got to make sure that the car can still start in the cold though, which is when the demand on the battery is highest and the voltage available to the ignition system is the lowest. I had a girlfriend with a Ford Capri that would run very nicely when it was running, but as it got colder it became harder and harder to start. I found out the spark plug gap was about 1.5mm. Reducing it to 1mm solved the problem.

[oby-]

So, what I get from this is to never change my plugs as it will only get stronger as the gap increases. Saves me a lot of work.

[ProDigit]

I used to have a 50cc scoot, which was actuallyabored out 63cc, and did some spark gap tests on them. Increase until rough ride, and decrease until rough ride.
Then get the gap that's exactly the middle of the two extremes. The engine ran by default too hot, at a too high compression ratio, so I used premium fuel only, as that helped top speed. On regular fuel, I could quite literally hear the engine oil boiling after a long ride.
Additionally it had a very weak stator (electric power generator).
This resulted me in having to decrease the spark plug gap, which decreased stator load, and allowed for more spark releases per ignition than when widening the gap. Every time we see a spark appear, it's not really a single spark. It's a multitude of electric current releases per second, just like lightning in the sky, following exactly the same path. Our eyes won't see any difference, but a slow mo camera can.

I did gain about 5mph, to a top speed of 55mph on that scoot, by actually decreasing the gap by about 20%.

[rustybritches]

I would like to see this test done again but with different plugs, heat ranges and gaps added to the scenario.

[chrishansen]

I'm really loving these new cams btr has been putting out, really pushing the limits of innovation on the LS

[KjV]

I experimented with spark plug gap in my own car. Heavily modified 2 litre turbo, running 20 psi. I gapped them down from 0.8mm to 0.6mm, to eliminate spark blowout. Doesn't affect horsepower much (other than the fact that the spark's not being blown out). But it *does* drastically affect emissions and fuel economy; both were measurably negatively affected. It's amazing what a difference such a small change makes.

[peanutbutterjellytme]

In my experience all that a huge plug gap does is help you find out if your coil is weak.

[derrickjohnson]

Thank you Richard! My favorite part of your videos are when you say, "we're live"!!!!

[gedavids]

My understanding of plug gap is that you basically want the biggest gap that your coil can handle under all driving conditions. The voltage required to jump the gap increases as gap increases and with the "air" pressure (hence why boost needs a smaller gap, or a stronger coil). Since GM spec'd a 0.040" gap for a typical LS, I'm thinking this strikes some kind of balance. Like it can jump a 0.100" gap, but it's not making anymore power than 0.040", so why? Or, I think more likely, it can jump 0.100" gap, but that will wipe out the coils in 3000 miles miles, so they made it 0.040' and they effectively last forever.

[samhicks]

*Indexing & side gapping*

I would index the plugs with index washers to point the plug gap to the intake valve, (Or between the intake/exhaust valve is fine) Then after the plugs have been indexed, i would cut back the ground electrode a bit known as SIDE GAPPING, cut the grounding strap untill the center electrode is not covered by the grounding strap. Insert the plug gapper at a 45* to measure the gap, increase plug SIDE gap about 15 thou from stock values, On a big block Chrysler is .35 STOCK increased to .45.

Noticeable idle quality and get up and go. Done on a 361 Big block Chrysler. Other notes: Left more of a complete burn of the A/F mixture <Tan colour on the porcelain part of the plug> little to no fouling of any kind aside from oil burning, Pretty good performance for a 'Tired" engine with compression ranging from 119 to 124 across the eight cylinders.

The negatives with the modification with side gapping plugs is that the plugs will wear on one side and chip away at the shoulder of the center electrode. Not only that but you will get less life of your plugs due to wearing on one side as previously stated.

If your engine burns excessive oil, the side gapping will make the problem worse as the oil splash can now "Put out" the spark and directly splash oil on the center electrode making your fouling worse and or make the engine run rough.

This is another thing to keep in mind, probably more pronounced on high compression methane racing applications is the the spark can be "Blown out" like a candle due to the turbulent A/F mix swirling in the combustion chamber.

Note: The ignition timing will change a tad due to the bigger gap, and also the ignition coil will fire the only needed voltage to jump the gap, meaning installing a 45K ignition coil is not a complete bolt on power, you need to increase the plug gap to get the ignition coil to send more voltage to jump the BIGGER gap, henc taking advantage of the bigger voltage coil output.

[MWR-lgqp]

Again, great data every gearhead Says they know the answer to. You sir, proved it and closed the books on gap. Thank you again for all your hard work.

[razbest]

A mate of mine in NewZealand was taught to tune cars any v8s 2 stroke out board's ect he has a heavy australian Hg Holden with a mild cam 327ci 600cfm 1850 vacuum seconds manual transmission, home made cold air induction box, tire diameter rear dif gearing matched for quarter miles, pacemaker extracters and some wonderfully ported iron cylinder heads by the famous local lawnmower small engine mechanic and the holley carbon tuning was his specialty along with his setting up the old twin point mallory distributor for correct dwell and advance weight curves all by feel, this car popped the front wheels of the ground about one inch when he hit second gear, i remember him adjusting spark plug gap it was always matched with the jetting of the carburettor regardless of what type, he said if jetting was lean open the gap to expose more fuel to the spark and close it up to stop rich mixtures from extinguishing the flame front .

[TEAMWRIGHTEOUS]

Also... We build drag motorcycles at our shop. We have a chassis dyno and get to do some of these test as well. But not near enough, and I really love watching your channel to see all the things you test.

And showing the pulls and showing the screen adds to your channel. Really enjoyed this episode as a whole. You done great on this one.

[MrJake-yxll]

Being a baby boomer and living through the evolution of standard coil ignition and the advent of CDI it didn't take us hot rodders long to figure out that plug gap was a sensitive thing when you were dealing with a basic coil ignition but once you get those nuclear reactor CDI systems going you could do all kinds of things with plug gap....
mainly speaking increase the gap to get more horsepower and torque.

It was a cool thing to experience when CDI came online in the '70s.

Thank you Richard once again testing is your bag and you are the best.

[jaderiddle]

My understanding of plug gap has always been to run as much as you can get away with. The theory being that more plug gap provides a larger flame front for more complete combustion. This might be what we’re seeing in the results of this experiment: the wider plug gap providing more complete combustion leading to ever-so-slightly more power (1% gain).

The downside to large plug gap is a higher voltage/energy requirement from your ignition system not to mention the higher potential to blow out spark, particularly on forced combustion applications or fuels with low AFR stoichs, for example alcohol fuels.

So there’s a balance to be found with plug gap vs spark blow out.