Good read about spark plug gaps and “side gaps”

[troutbum70 857]

Mid 70's I think in my part of the country or real early 80's. All though they were experimenting with it a long time before that.

[WHX?? 48,764]

On 11/14/2019 at 9:15 PM, troutbum63 said:

plugs of a few years ago came from with no ground strap allowing to fire any where in the 360 degree circle.

Those are called surface fire or surface gap plugs commonly used in two stroke outboards. Not really sure why but I would guess as to keep the plug from fouling? Do not know why they never caught on in other motors. I don't thing they are used in anything anymore. 

From the web...

NGK Surface Gap spark plugs are specialty plugs that are nearly immune to pre-ignition, and usually require special high-energy ignition systems. They feature trivalent metal plating, corrugated ribs, pure alumina silicate ceramic insulators, copper cores, and triple seals. These plug characteristics provide superior anti-corrosion and anti-seizing properties, superior strength, and better heat transfer—as well as preventing flashover and leakage.

[pfrederi 17,663]

12 hours ago, CCW said:

According to the Kohler service manual I download from RS the gap should be .025.  Am I missing something regarding the .035?

 

 

 

Depends on what Kohler specified during that time frame.

 

Older  K series service manual is .025 for all gasoline engines.  Later K series manual bumped it to .035 for battery ignition big blocks but kept .025 for magneto and small blocks.  Interesting no mention of breaker less.  Spark plug torque stayed the same at 27 ft/lbs.  Magnums had .025 for all singles but the spark plug torque was reduced to 18-22 ft/lbs.

 

Since Kohler couldn't decide consistently I wouldn't lose that much sleep over plug gap and i sure would not waste my time trying to index it.  These are garden tractors not Ferrari's....

 

 

[WVHillbilly520H 10,373]

[AHS 1,439]

4 hours ago, WHX24 said:

Those are called surface fire or surface gap plugs commonly used in two stroke outboards. Not really sure why but I would guess as to keep the plug from fouling? Do not know why they never caught on in other motors. I don't thing they are used in anything anymore. 

From the web...

NGK Surface Gap spark plugs are specialty plugs that are nearly immune to pre-ignition, and usually require special high-energy ignition systems. They feature trivalent metal plating, corrugated ribs, pure alumina silicate ceramic insulators, copper cores, and triple seals. These plug characteristics provide superior anti-corrosion and anti-seizing properties, superior strength, and better heat transfer—as well as preventing flashover and leakage.

Oh ya! Those spark plugs came in the old mercury snowmobiles.... which was a boat motor.. sort of.. the cylinders would lay horizontal instead of vertical.

[Tractorhead 9,064]

When i reworked my Quadbike for racing purposes, i fightening with each little possibility i have.

I don‘t want to change the Engine, itself but i wanna see, how much Power i can grasp out of this „thing“.

The base Engine was a 300ccm 4 Valve Aircooled with stock 19 HP.

 

So i firstly changed the Carb from a vaccum controlled to a boosted one with accelerations pump.

Than a friend bore the block up to 320ccm, what was as a max. possible.

We inserted a coated special piston from Mahle, specific made.

Next stage i did was the complete rework of the Head  by increasing the intake channel in rough,

built a swirl channel to the intake Valves to get better mixture and increases the Intake valves at one and outlet Valves at two size up.

 

Next change was a programmable Ignition, where i can programm my own setup curve,

whilst reprogramming i trying different settings and Sparkplugs and ended up with the Bosch type below in Pict.

 

 

 

Than i increased the exhaust line ( ain‘t smoothen it) and added an 1,6 times bigger exhaust Manifold on the outlet with a bimetall flaped Muffler on the end.

After that complete setup i do several times finetuning with a Lambda sensor and changed the nozzels to their maximum.

 

The final stage brought all in all 38HP on a Dyno in 3 runs continousely under witness.

Single term run was 43 HP but it drops quickly back to 38 HP what stay’s in long term rum.

i know all was doing it’s part of that result and i cannot honestly say, how much the sparkplug allone brings.

 

 

But once was significant felt, the Engine runns definitely felt smoother at higher rpm‘s and the acceleration 

felt be a bit revvning than compared to a standart spark Plug with 0,65mm gap i used before.

 

Even on larger jumps i like the quick revvening for stabilizing the flight with playing a bit on the Throttle.

 

I drove also the same spark plug on my KTM with same results

Here i also felt, the revvning is more accurate.

 

But i doubt, that just a sparkplug make a smallengine to a high torque runner.

It definitely supports a better combustion with less missfires, but misfires is mostly a sign of a inaccurate setup.

But i see no advance on my Tractorengine, here i find it‘s better, to change regulary my sparkplug.

[oilwell1415 563]

On 3/3/2020 at 7:27 AM, WHX24 said:

Those are called surface fire or surface gap plugs commonly used in two stroke outboards. Not really sure why but I would guess as to keep the plug from fouling? Do not know why they never caught on in other motors. I don't thing they are used in anything anymore. 

From the web...

NGK Surface Gap spark plugs are specialty plugs that are nearly immune to pre-ignition, and usually require special high-energy ignition systems. They feature trivalent metal plating, corrugated ribs, pure alumina silicate ceramic insulators, copper cores, and triple seals. These plug characteristics provide superior anti-corrosion and anti-seizing properties, superior strength, and better heat transfer—as well as preventing flashover and leakage.

The surface gap plugs are typically used in applications where the piston would hit a conventional electrode.  Small two strokes with high compression ratios don't have much clearance.  The side electrode is also the hardest part to get heat out of between cycles, so eliminating it gets rid of a significant hot spot in those high compression engines.

 

Just curious, but how do you guys quantify any improvement you would get from this?  Looks like a good way to spend a lot of time and effort optimizing something that you really can't confirm the results of.  I've spent hours on a dyno with 250-750 hp engines and stuff like this is what you do when you are looking for that last 5 hp at any cost.  Doesn't seem like it's worth it on a tractor unless you have a noticeable misfire and that is likely from a bad component.

[ebinmaine 67,266]

3 minutes ago, oilwell1415 said:

Just curious, but how do you guys quantify any improvement you would get from this

The only thing that I could really see would be a slim chance possibility of easier starting.

 

I've never even been around a single cylinder race engine but I can't imagine that even Dyno differences would be any more than negligible on a stock Kohler 10 or 20 horse or whatever...

 

For the sake of curiosity I would love for somebody to prove me incorrect but it's not something I would probably try because of the time involved.

 

 

[WHX?? 48,764]

On 3/3/2020 at 8:26 AM, pfrederi said:

These are garden tractors not Ferrari's....

 

1 hour ago, oilwell1415 said:

Doesn't seem like it's worth it on a tractor

We know... we just like yakin about this kinda crap...

[oilwell1415 563]

1 hour ago, ebinmaine said:

The only thing that I could really see would be a slim chance possibility of easier starting.

 

I've never even been around a single cylinder race engine but I can't imagine that even Dyno differences would be any more than negligible on a stock Kohler 10 or 20 horse or whatever...

 

For the sake of curiosity I would love for somebody to prove me incorrect but it's not something I would probably try because of the time involved.

 

 

I'm curious, mainly because the combustion chamber design on a lot of old engines, particularly the flatheads, is terrible.  I think there could be some gains there, but it's nothing you would be able to feel.  You could definitely see them on a dyno, but who has a dyno this size?  We had one in the engineering lab when I was in college and it's amazing what kind of gains you can get in a "stock" engine.  But it was nothing that could be quantified without instrumentation of come kind.  I didn't get to go to our mini baja race, but I'm told that the "stock" 8hp Briggs I built for the car got a lot of odd looks when people heard it run.

 

[ebinmaine 67,266]

1 hour ago, oilwell1415 said:

I'm curious, mainly because the combustion chamber design on a lot of old engines, particularly the flatheads, is terrible.  I think there could be some gains there, but it's nothing you would be able to feel.  You could definitely see them on a dyno, but who has a dyno this size?  We had one in the engineering lab when I was in college and it's amazing what kind of gains you can get in a "stock" engine.  But it was nothing that could be quantified without instrumentation of come kind.  I didn't get to go to our mini baja race, but I'm told that the "stock" 8hp Briggs I built for the car got a lot of odd looks when people heard it run.

 

I don't know why I didn't think of this until just now.

My small engine shop that I use on a regular basis is also a  builder of race engines.

He's told me at least a couple different times that you can easily and inexpensively get 1.5 times the current horsepower out of any given small single-engine.

 

I should run this by him and see what he says.

 

[oilwell1415 563]

The governor kills them, even below max rpm.  That where I found most of the power on our Briggs.  If the rpm is governed to 3800 the governor will start kicking in about 3100-3200.  It's been 20 years ago, but IIRC our 8 hp engine only made about 4-5 hp on the governor.  You had to manually hold the throttle wide open for it to make 8hp.  I was able to get it up to 6 o 7 on the governor and keep the governor from starting to kick in until about 3500 rpm just by playing with spring rate and preload.  That was probably the biggest single change.  The rules didn't say you had to use a head gasket, so I took it out to raise compression.  Everything was blueprinted to make it the best it could be.  I think I ended up getting about 8.5 hp out of it with it still being governed to 3800.

[Greentored 3,201]

Like @WHX24 said we just like yakkin, so here some more useless info for you all

 I dont know how to leave ANYTHING alone, especially if it burns fuel and has a piston. 30+ years of my life has been 'wasted' trying to trying to prove people wrong, experimenting, and trying to wring every ounce of power out of everything from 3hp go karts to 800hp big blocks. Ive had a lot of success, and made babies in the oil pan and oiled down the asphalt a few times as well.

We all know ignition timing and curve (when talking about engines with advance mechanisms) are an absolute performance improvement when dialed in, so we'll skip that stuff. As for the rest, the ONLY time I have ever experienced a noticeable power gain is when swapping from points to electronic in an automotive situation. ANY electronic conversion. On a V8, gains are very noticeable, even on the seat of the pants-butt dyno. Everything else- fancy wires, 14 electrode golden plugs, hot coils, spark boxes, big plug gaps, etc...  they all do help, but the power gains are negligible and often cant even be picked up on an engine dyno unless it is a state of the art, dead repeatable setup. What a good, hot spark and all those fancy parts WILL do is provide easier starting and less fouling, every single time.

about 7 years ago, I swapped out a basic mallory electronic ignition and accel super coil in my street/strip 66 cutlass (496 big block chevy, mid 10 second car on slicks) for a brand new MSD billet distributor, box, wires, coil, etc...   700+ dollars basically gave me an adjustable rev limiter and a cleaner looking spark plug. Gains at the track were nothing-zip, zilch, zero.

  Keep your parts in good working order, make sure your plug wire and spark plug boot are not cracked, buy a good plug, side gap it and run the gap as wide as you can without misfires, and call it a day. It will probably start better, thats about it

 

Edited March 6, 2020 by Greentored

[Pullstart 62,783]

I wasn’t aiming for such an in depth discussion and have very little to add, but thanks everyone for your inputs on such a common yet overlooked part of gasoline internal combustion engines!  

[Tractorhead 9,064]

Eric, good Enginetuning wasn’t Tuning by simple.

 

Sure you can tweak few parts simply for a quick „ upgrade“ because a Stockengine wasn‘t built to run on it’s limit.

A stock engine is primary built for long lasting,

that means, keep the combustion and runing envoirement in a safe term, where several reserves are possible.

An 8HP Engine can be easily brought up to 12-16 Hp by rework a bit, but how long should that Engine lasts after that.

 

It is not a wizard trick i. Eg. to increasing of the static middle pressure by planed the head a bit,

So you can simply bring an engine to a bit quicker revvening, added with more advance in ignition you get a much 

agile revvning engine, but all that goes on last.

Even rework on Valve settings brings a lot without touching the Engine itself.

sometimes it‘s enough to push the ignition advance from 32deg btc to 36 deg btc.

the question is how hard it starts than in cold envoiremental with choke.

in racing purposes i run my KTM also with 100 octane fuel and alcohol up to 42deg. btc - a brutforce Engine but no longlife Engine at all. This Engine lasts normally 3 Races sometimes 4, than it must be completely checked and mostly reworked because of excessive materialstress.

we grasp 98HP of 770ccm cont. Power. By 136Kg. 

but all that tuning results also in more heat and much more pressure, where gaskets and Engineblock, bearings Valves and all

moving and static parts incl. head must be withstand.

 

Our Tractorengines, they ain‘t built for. The rpm is controlled by governor.

you can overrule the governor, but that mostly is a short term thing, because this Engines are not built for higher rpm‘s.

They can be improved, but another question is the invest you must do.

 

for a shortterm Engine like a race Engine this components will be improved or reworked and brought to their limits,

on a stock engine it can be critical for all day purpose with stock parts.

but if you have an Engine you wanna play with - do it.

it can be funny😎 to see what reserves are in, but don‘t calculate with long term last.

 

 

[Greentored 3,201]

22 hours ago, pullstart said:

I wasn’t aiming for such an in depth discussion and have very little to add, but thanks everyone for your inputs on such a common yet overlooked part of gasoline internal combustion engines!  

This has been a GREAT discussion, thank you for starting it!