Good read about spark plug gaps and “side gaps”

[Pullstart 62,786]

https://www.badasscars.com/index.cfm/page/ptype=product/product_id=73/category_id=13/mode=prod/prd73.htm

 

I found this this interesting read and thought it would be worth sharing.  I wonder if side gapping would help such a small engine as ours?  @fast88pu any input from the pulling/power world of small engines?

 

from the above link... “This exposes the spark to the open cylinder and combustion area more and prevents the shrouding that the full length ground strap tends to do on regular plugs.”

[JoeM 7,871]

Kind of reminds me of the E3 Diamond Fire Plug design, open center.

I know 40 some years ago when drag racing, we spent a lot of time trying to get hundreds of a second. Spark plugs were a big deal, changing, type, indexing, etc. all made some difference.

Wonder what the pullers do?

[ebinmaine 67,268]

5 hours ago, MrOiluj52 said:

indexing

I remember that being a big help to some fire breathing metal monster street and drag engines

[Herder 2,354]

Kool read!!  I have heard of side gapping, but was unclear of how it was done.  I am going to have to head out to the shop and do some experimenting on the old C-160. 

The plugs in my small block ford have a reduced gap and it was a noticeable improvement.  Believe me it took some work to get it right.   

[troutbum70 857]

That was an interesting read as I live a sheltered life, had no clue what side gaping would be. But it seems to me that the term end gaping would be more appropriate, but that is just my sheltered mind thinking.  I suppose this concept is where the revolutionary plugs of a few years ago came from with no ground strap allowing to fire any where in the 360 degree circle.

[Stepney 2,325]

Makes me think back to my Rupp Magnum I used to drive. Had the Bosch surface-gapped spark plugs. No way to set anything there and the spark location was totally haphazard. They must have worked as claimed .. they were original and nearly 50 years old. 

[fast88pu 3,324]

On November 14, 2019 at 11:39 AM, pullstart said:

https://www.badasscars.com/index.cfm/page/ptype=product/product_id=73/category_id=13/mode=prod/prd73.htm

 

I found this this interesting read and thought it would be worth sharing.  I wonder if side gapping would help such a small engine as ours?  @fast88pu any input from the pulling/power world of small engines?

 

from the above link... “This exposes the spark to the open cylinder and combustion area more and prevents the shrouding that the full length ground strap tends to do on regular plugs.”

I've never messed with it kevin. I've always used original recommended plugs for the engine. But I will be trying a new setup on the restomod lawn ranger built predator. An autolite race plug

[Macgyver 90]

I'm going to have to try this on an Onan engine. The plugs sit in a pocket 

so getting the spark out by cutting the plug like they show might improve

ignition.

[ebinmaine 67,268]

8 hours ago, Macgyver said:

I'm going to have to try this on an Onan engine. The plugs sit in a pocket 

so getting the spark out by cutting the plug like they show might improve

ignition.

Another thing to consider doing is called "indexing" the plug.

Use special washers of specific thickness to turn plug gap face toward the combustion chamber.

 

I don't know how Onan engines are set-up at all. I've seen RACE Kohler flatheads with the plug moved to above the top of the Piston in the head.

 

 

The science behind these modifications is very real and works wonders in HIGH HP engines.

It certainly can't hurt to try but I don't know how much gain one would get from a single cylinder or small 2 cylinder.

 

Perhaps a bit smoother idle or 1/2 to 1 hp??

 

[lynnmor 7,302]

All a spark plug can do is ignite the mixture.  If you have a miss or backfire with new plugs, it is time to find the real problem.  A highly modified engine might benefit from experimenting with spark plugs if the modification led to a misfire.

[AHS 1,439]

7 hours ago, ebinmaine said:

Another thing to consider doing is called "indexing" the plug.

Use special washers of specific thickness to turn plug gap face toward the combustion chamber.

 

I don't know how Onan engines are set-up at all. I've seen RACE Kohler flatheads with the plug moved to above the top of the Piston in the head.

 

 

The science behind these modifications is very real and works wonders in HIGH HP engines.

It certainly can't hurt to try but I don't know how much gain one would get from a single cylinder or small 2 cylinder.

 

Perhaps a bit smoother idle or 1/2 to 1 hp??

 

Yes, I have read about that on snowmobiles! I have some colored washers, somewhere!

[AHS 1,439]

What would the indexing be for like the K series engine? .035? I usually just take a spark plug and throw it in there! 

 

 

[ebinmaine 67,268]

23 minutes ago, AHS said:

What would the indexing be for like the K series engine? .035? I usually just take a spark plug and throw it in there! 

 

 

Indexing is where the Gap is pointing...

 

Actual gap varies by model and ignition type.

 

[Oldskool 6,640]

16 hours ago, AHS said:

What would the indexing be for like the K series engine? .035? I usually just take a spark plug and throw it in there! 

 

 

Indexing refers to a process where extra washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in a desired direction.

[AHS 1,439]

Oops! The gap on K series! Have to read the owners manuel!

[Macgyver 90]

The plugs for the Onans don't use washers/ gaskets they are tapered seat. That and the pocket in the head makes me think that the side gap method might lead to better ignition.

[Greentored 3,201]

I have a chopped 53 Harley with a barely streetable, poked and stroked 92CI and a set of shovel heads on top, and can tell you for a fact that side gapping the plugs results in much easier starting and they seem to last 3 times as long. 

Power-wise, couldnt tell ya. I know its all I can do to point it in a straight line, keep my rearend from sliding off the seat, and not wet my pants- way too much going on to concentrate on an extra 1 or 2hp 

By all means, on these little engines- do it and report back!

[WHX?? 48,770]

We always indexed the plugs on our Harleys, even when adding a second plug to the head which was always done on worked over motors. Never heard of short strapping till now. Dan @Achto care to comment on this? 

[Achto 27,502]

Interesting read @pullstart. Cutting the strap back is a new one for me. Indexing the plug has been a common practice for years. I have not messed around indexing the plug on a Kohler. With the plug on a flat head engine being miles away from the cylinder to begin with, I guess it wouldn't hurt to give it a try.

[CCW 1,292]

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

 

[ebinmaine 67,268]

7 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?

 

No, yer good... 

35 is used on more modern HEI ignition or whatever.

@AHS mighta been thinking of a different machine.

The cold air up north here messes with our heads.

[AHS 1,439]

1 hour ago, ebinmaine said:

No, yer good... 

35 is used on more modern HEI ignition or whatever.

@AHS mighta been thinking of a different machine.

The cold air up north here messes with our heads.

I was thinking .035” is what they gapped spark plugs right from the factory. @ebinmaine

[ebinmaine 67,268]

3 minutes ago, AHS said:

I was thinking .035” is what they gapped spark plugs right from the factory. @ebinmaine

Depends on the plug.

They're gapped anywhere from .025 to as much as .080. (for some cars)

 

The small engine plugs I buy are gapped at .025.

 

[AHS 1,439]

@ebinmaine what year did they switch from leaded gas to unleaded gas? In the 70’s?

[ebinmaine 67,268]

1 minute ago, AHS said:

@ebinmaine what year did they switch from leaded gas to unleaded gas? In the 70’s?

I'm not positive on that but I think the valve seats in Chevy 350 cylinder heads changed around 1973 or 4

 

After that there were other changes to help with unleaded fuel. I think that was around the first year though.

 

@WVHillbilly520H Jeff do you know that one?