Side gap spark plug

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andyofcolumbusmerkur
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Side gap spark plug

Post by andyofcolumbusmerkur »

Anyone have side gapped spark plugs in there car? I was thinking of trying it on an extra set of 764's to see if I can feel a difference. I really don't care about plug life or anything. Anyone use them for an extended time as in on a street car?
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Ed Lijewski
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Re: Side gap spark plug

Post by Ed Lijewski »

https://en.m.wikipedia.org/wiki/SplitFire_spark_plug

I ran a set in s Scorpio until later at a repair garage tech said the company's P.R. on performance gain was bull excrement.

YMMV
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andyofcolumbusmerkur
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Re: Side gap spark plug

Post by andyofcolumbusmerkur »

Ya I doubt I would see any improvement on turbo street car. Just for the record I am talking about removing a small amount of electrode and not talking about using different plugs. Like split fire or quad fire or anything.
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zxr250cc
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Re: Side gap spark plug

Post by zxr250cc »

Hi all,

I would think that indexing the plugs to have the gap aimed at the intake valve would be a better, if slight, improvement than trying to file the plug like some makers did in the past for race version plugs. Just a thought.

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andyofcolumbusmerkur
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Re: Side gap spark plug

Post by andyofcolumbusmerkur »

You can also do that completely different thing. Common on high C/R builds.
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Re: Side gap spark plug

Post by andyofcolumbusmerkur »

I have heard of washer kits that allow indexing (aiming) of the plug electrode but have never scene those for sale anywhere.
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zxr250cc
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Re: Side gap spark plug

Post by zxr250cc »

Hi all,

It seems they are still offered in some sites:

https://www.ebay.com/itm/294444767456?c ... 9a7355bbf6

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andyofcolumbusmerkur
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Re: Side gap spark plug

Post by andyofcolumbusmerkur »

If you look at the writing on this vintage package it states the purpose is to "correctly" locate the center electrode. I'm not sure if they mean aiming the open gap towards the exhaust valve or just making sure nothing makes physical contact.
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john keefe
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Re: Side gap spark plug

Post by john keefe »

IIRC, it was old school to either turn the electrode toward center of the squish where air/fuel was traveling slowest, or toward the intake valve (to "start" the burn early while it swirls), or toward the exhaust to get a complete burn and so that the electrode bar acts as a break and keeps the plug gap from getting soaked with fuel... depending on your bias. With turbos/SC's the debate was usually whether the high pressure/flow required turning the electrode away from the intake so it wouldn't "blow out" the spark. If you were building a serious engine, the only sure way to know was to dyno and test all three positions. Lot of work to index 8 plugs for 3 positions.

More often, washers were simply used to make sure the electrode was pointed away from a high dome piston so the piston travel wouldn't squash the electrode, or to recess the plug away from the chamber altogether so there was no chance the dome could hit it.

You painted a line down the plug, or a bright dot on the hex to show where the electrode sat (now you could do it with a sharpy). Probably not needed these days with the maximized combustion chambers, and specific heat length plugs that can only seat to a certain depth.
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andyofcolumbusmerkur
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Re: Side gap spark plug

Post by andyofcolumbusmerkur »

andyofcolumbusmerkur wrote: Sat Oct 09, 2021 7:23 pm Anyone have side gapped spark plugs in there car? I was thinking of trying it on an extra set of 764's to see if I can feel a difference. I really don't care about plug life or anything. Anyone use them for an extended time as in on a street car?
So anybody side gap the spark plugs on our low compression cars and how long would you say they lasted driving them on the street?
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zxr250cc
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Re: Side gap spark plug

Post by zxr250cc »

Hi all,

As the Autolite 764/104 plugs are standard nickel copper construction I would expect them to act as normal for durability. I also use the same construction type of Motorcraft plugs (made by Autolite in the past) in an SVT Focus and they are good for about thirty thousand miles or so. I could use the 764/104 plugs in a 24 valve Taurus, they are an exact match surprisingly, but the trouble of changing the rear three plugs (have to remove the intake manifold) makes me choose platinum plugs so I don't have to change them as often.

The 764 or 104 should be good for twenty to thirty thousand in the XR as well, I would expect, when used as a DD, not racing. As cheap as they are you could use them for only a year or two and change them as a maintenance item like the air filter without worrying if you felt like it. I bought six sets initially as I was considering indexing the plugs but in the end kept them as spares. The threads are of course randomly made with respect to where the gap is and I planned to make an index mark on the plugs and aim the open gap at the intake valve. In the end it seemed like more effort than benefit for a street car.

I checked in Rock Auto and 104 plugs are $1.45 each at this time. It is easy to stock up as a good pack rat at that price...

YMMV

Cheers
1986 XR4Ti Mineral Blue Metallic
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