Spark Plug gap Toro says .40 Kohler says .30

[266-H 1]

I have a 1995 266-h with a CV16s twin,  my buddy has the 267-h same motor same displacement 1 year newer for the 267.  They both have a gap of .40 in the toro manual. 

 

Champion RC12YC plugs

 

But...

 

If you looked up Kohler CV16s, CV17, Cv19 command twins they all say .30 for the spark plug gap.

 

I've done .40 but wondering why the difference.?

 

Maybe after the 1995-2000 .40" was the gap to use and later they change to .30.  

 

Anyone know?

 

They must have made two 16v twins as one of them is not anything like mine.   Mine looks the exactly the same as the 267 and 269-h command motors.  Same displacement too. 624 cc.  But all of them say gap .40 in toro manual.

This is what the motor looks like.

 

And not this one.

Not this 16vs

 

[JoeM 7,608]

I always lean toward the engine mfg. specs. Hey if it runs good at 40 why change?? 

 

welcome to square!

[squonk 38,846]

The engine itself really doesn't care what the gap is as long as the plug is correct and has the proper heat range. Now the ignition coil cares a lot. Wider gap, more stress on the coil

[WHX?? 46,703]

Split the difference and run .35? 40 seems awfull wide but maybe has a high output ignition? No familiar with that motor.. 

[shallowwatersailor 3,213]

Like Mike said, the smaller gap is easier on the coil. Back in the '60s and '70s we would run a smaller gap on our car's engine in the winter for this reason. Go with what Kohler recommends.

Edited September 1, 2021 by shallowwatersailor

[266-H 1]

1 hour ago, JoeM said:

I always lean toward the engine mfg. specs. Hey if it runs good at 40 why change?? 

 

welcome to square!

It has 800 hours on it and still runs like a top.   All i've done is change the oil.filter and transmission fluid 1 time.  

If its not Broke don't fix it!   But maybe .35 would be better on the old gooses coils. 

 

I was just curious if I had been gaping wrong all this time and why Toro would print out .40 in all the 260 series manuals.   

 

I'm thinking in 1995 they found .40 better but now when I look up Kohler Command they are maybe quoting newer 2006 and newer engines that happen to have the same name but its not 1995 specs.  Hoping and old Toro mechanic would know.

 

 

 

Edited September 1, 2021 by 266-H

[lynnmor 6,762]

That is an awfully large gap either way, you can get 5 to 7 pennies in there!  

 

Sorry, just the toolmaker in me.

[Handy Don 10,567]

4 minutes ago, lynnmor said:

That is an awfully large gap either way, you can get 5 to 7 pennies in there!  

 

Sorry, just the toolmaker in me.

Good catch!

 

[gwest_ca-(File Mod) 10,488]

The CV16 Twins use a CV18 spec number.

Click on the engine in the link.

 

[JoeM 7,608]

13 hours ago, 266-H said:

gaping wrong all this time

Not really, probably can't tell the difference. I just go back to the drag days when we tried a few things to pick up a few hundreds of a second consistently. If it purrs at .040 it is right. 

The plug heat range has more effect then a few thousands on the gap. Some of the older Kohler's need a hotter spark to overcome oil fouling. 

In your case you have a magneto, it is putting out all it got.... every time. More important on your machine is the coil gap. A few thousands difference in coil gap can change the timing and spark intensity. Most of the time a sure sign of this is hard starting. The old "close as you can get it" is not right and at that point the mfg. recommendations are the best.

Hot vs. Cold Plug the hotter plugs tip is further away from the conducting metal and will stay warmer between firing. 

On the plugs shown the most important part of this heat transfer is up inside. 

 

You question is good, but I don't think there is a cut and dry answer. It can be that that plug was manufactured for many different applications at the time and it may have been a cost saving process that worked across the board.