1" reach surface gap plug

[gene cooley]

I am looking for a 1" reach, 14mm, tapered seat surface gap plug. The original plugs (similar to one shown) gets hit by the piston and the ground strap gets closed up.
I am using a 3/4 or 7/8 reach plug now, but I would like to get the plug a little further out of the hole.
I considered indexing rings but would prefer to use the surface gap if one is available.
This is for the Ecotec in the 600.
Thanks.

 

[Dr.Jeff]

As you know many plug manufacturers offer "racing" plugs that are surface gap. You might be able to find the specific part number for your application by looking at the manufacturer's catalog (should be able to find them online). They usually have a section that explains all of their numbering systems; what each letter and number indicates for the specific plug design. That way you can determine the reach, heat range, type (surface gap), thread, etc, off the chart and know what plug to look for by it's part number. Back when catalogs were printed this was pretty easy to do, but ironically it seems things aren't always so readily available online unfortunately. So I'm not certain how easy it might be to do now. If you have a old time parts store with a old time employee they might still have all of the resources to do this.

 

[gene cooley]

As you know many plug manufacturers offer "racing" plugs that are surface gap. You might be able to find the specific part number for your application by looking at the manufacturer's catalog (should be able to find them online). They usually have a section that explains all of their numbering systems; what each letter and number indicates for the specific plug design. That way you can determine the reach, heat range, type (surface gap), thread, etc, off the chart and know what plug to look for by it's part number. Back when catalogs were printed this was pretty easy to do, but ironically it seems things aren't always so readily available online unfortunately. So I'm not certain how easy it might be to do now. If you have a old time parts store with a old time employee they might still have all of the resources to do this.

If I remember correctly GM's Ecotec race heads were machined for more commonly available plugs. 1" reach tapered was changed to 3/4" reach gasketed plugs.
I've done a lot of looking with no luck on surface gaps. It looks like I need to use a spacer to place the plug 0.025" (guess) further away from the piston.
One thing I did learn about surface gaps is they don't have a heat range because of their construction.

 

[Dr.Jeff]

I haven't looked into "race" plugs in ages, so not sure what the current market is. I do recall that for motorcycles NGK had options with a side mounted electrode (not surface gap, but also not extending down into the chamber). Seems Champion was a big brand for surface gap back then. Now there are all those multi electrode plugs, maybe some of them extend shallower/less into the chamber? I also recall hearing about guys cutting off the electrode to make 'affordable' race plugs out of regular ones, but I wouldn't think that works...I wouldn't want to try. I'm trying to remember the other plug that was popular for this sort of 'race' design but drawing a blank. Do any of those ultra small tip/exotic metal (e.g. iridium or whatever) plugs have a reduced extended length on the tip?

 

[gene cooley]

I haven't looked into "race" plugs in ages, so not sure what the current market is. I do recall that for motorcycles NGK had options with a side mounted electrode (not surface gap, but also not extending down into the chamber). Seems Champion was a big brand for surface gap back then. Now there are all those multi electrode plugs, maybe some of them extend shallower/less into the chamber? I also recall hearing about guys cutting off the electrode to make 'affordable' race plugs out of regular ones, but I wouldn't think that works...I wouldn't want to try. I'm trying to remember the other plug that was popular for this sort of 'race' design but drawing a blank. Do any of those ultra small tip/exotic metal (e.g. iridium or whatever) plugs have a reduced extended length on the tip?

If they do I haven't found any, but then my search was mostly on surface gaps. The 1" tapered seems to limit choices more than any other dimension.
It could be that I could use the "triple" plugs with a spacer and reduce the (slight) increase in combustion chamber volume that I would have with single ground strap plugs. Yes, I readily admit I am nitpicking here, but if it just means buying a different style of plug it can't hurt.
I have considered bending or cutting the ground strap to get it away from the piston,
but like you I'm kind of afraid of this.

I'm starting to think the "triples" are the way to go.

 

[Dr.Jeff]

The 1" tapered seems to limit choices more than any other dimension.

Would modifying the spark plug holes for a different type/size plug be worth it? Perhaps convert them to a straight thread, or use spark plug hole repair inserts to change them completely to another size.

 

[gene cooley]

Would modifying the spark plug holes for a different type/size plug be worth it? Perhaps convert them to a straight thread, or use spark plug hole repair inserts to change them completely to another size.

I have not gone back to the GM Ecotec Build Book but as noted earlier I think that's what GM did on their race heads. I am trying to find a simpler solution (at least for the moment) and the surface gap appears/appeared to offer that.
There's a couple of months of the autocross season left and that along with a possible major rule change in Emod being announced as early as tomorrow sorta takes away my enthusiasm for tearing down a perfectly good engine for maybe 10 hp. Might have to later......
I'll have a look at inserts and see if anything there helps. Good thought.