Surface gap spark plugs

[Kahuna]

Does anyone have any experience using surface gap plugs? I realize they need additional voltage to fire over the standard type. I may have a clearance problem, and these seem like they night help. Anyone?
Thanks
Jim

[af2]

What are you building???

[ausbullet]

Does anyone have any experience using surface gap plugs? I realize they need additional voltage to fire over the standard type. I may have a clearance problem, and these seem like they night help. Anyone?
Thanks
Jim

Yes I have run them in a previous engine project and they worked fine.
The only comment I can offer is that the motor idled fine with the surface gaps, like it had stock cams, fitted a set of J gaps and the idle got a large lope in it, other than that and they don't wear out, no other faults or benefits were found.

Steve

[Kahuna]

Ausbullet: Thanks for the response. I really appreciate it.

AF2: The application is a Ford flathead, with stock appearing Canadian aluminum heads. The cam has a net lift of .400". My concern is with the squish clearance and the hope that the heads do not need to be modified beyond edge grinding. Currently, I think I'll be very close to the exhaust valve, with no opportunity to utilize a standard plug.

[af2]

I see the problem!
I have always run that plug in a 2 stroke but would also try it in a 4 stoke application. An engine is an engine regardless!

[dan miller]

Surface gap spark plugs are not in widespread use, so it logically follows that they must have a down side. They do seem like SUCH a good idea.

I suspect that it might be that the spark kernel exposes less surface area than a conventional spark plug. Or, possibly the combustible mixture within a conventional spark plug (between the insulator and the body) is a factor.

I doubt that it’s an electrical issue, as some of the modern ignitions are plenty stout.

Any ideas? Inquiring minds want to know. lol

Danny

[ausbullet]

Surface gap spark plugs are not in widespread use, so it logically follows that they must have a down side. They do seem like SUCH a good idea.

I suspect that it might be that the spark kernel exposes less surface area than a conventional spark plug. Or, possibly the combustible mixture within a conventional spark plug (between the insulator and the body) is a factor.

I doubt that it’s an electrical issue, as some of the modern ignitions are plenty stout.

Any ideas? Inquiring minds want to know. lol

Danny

You need a real good CDI to drive a surface gap.
Mercruiser used them in the 427 circa 1970, and again in the 900SC circa 2000, with there Thunderbolt CD ignition, which is what I used run the surface gap.
On the Thunderbolt ignition, when I sent it to MoTeC to check compatability with there ECU, Richard told me it wasn't the most powerfull or fastest rise time CDI but it was the best overall.

[Kahuna]

My understanding in looking into the feasibility of using these is that a good ignition is necessary, along with an HEI type cap (with the electrical terminals spaced far apart). But, that it isn't necessary to run a CDI. Guess I'll find out..
Thanks to all for the info
Jim

[sbwrench]

They are used extensively in motorcycle road racing applications.Many with stock ignition and stock stick type coils. They work well and last a long time.

[OldsMan]

Downside to surface gap sparkplugs, is they will foul faster as they run cooler.

[David Redszus]

Surface gap plugs were developed to eliminate the problem of burning off the ground strap. While the center electrode heat range can be adjusted by altering the thermal path length, little can be done about the J strap.

Surface gap plugs will last a long time, are less subject to destruction in a detonating enviornment but will foul easily.

The primary downside is that there is little charge motion in the gap which results in an increased ignition delay. And adjusting the gap is a bit of a pain.

Bosch makes an extended tip, surface gap plug that overcomes these difficulties but the gap cannot be adjusted and it requires about as much electical energy as your everyday arc welder.

[maxracesoftware]

we just Dyno tested the Champion "Surface-Gap" style plugs
in Jeff Colletta's NPS BBC632cid engine,

the Dyno results were the TQ and HP Curves were more smooth,
removed a few tiny peaks/valleys in Power Curve

seem to work OK w/NOS also

July 17-20th , 2008
Joliet , Illinois Nostaglia Pro Street
FINALS
1 NPS 4 Jeff Colletta Walker LA '00 Camaro Chev 632 0.034 7.578 181.86
3000 NPS 3 Kevin Parent Rochtester Hills Mi '69 Nova Chev 632 0.036 7.631 182.87

http://www.nmcadigital.com/forums/showthread.php?t=9987

Jeff's 632 (no NOS, Motor only) 1316 Peak HP on this Run
1322 Peak HP on the next Dyno Run

http://s123.photobucket.com/albums/o287 ... 316-HP.flv

[ausbullet]

Downside to surface gap sparkplugs, is they will foul faster as they run cooler.

Is that why they were used from the 60's in Mercury and OMC outboards.

The Mercury's had no thermostat in the cooling system.

In the late 70's Mercury Racing V6 T3's with constant flow type injection on Alcohol or Petrol at a 20:1 oil mix the surface gaps would never foul up, even idling around.

[Lctoliver]

I have a 2012 Mustang 3.7L v6 - stock engine and want to start adding some performance upgrades, not a lot, just a few to bump up the HP a little bit. So one of the things I want to do is to change to surface gap spark plugs. Do I absolutely have to have a higher voltage ignition system in order to install and use surface gap plugs? My current ignition system is stock.

[Tom68]

I have a 2012 Mustang 3.7L v6 - stock engine and want to start adding some performance upgrades, not a lot, just a few to bump up the HP a little bit. So one of the things I want to do is to change to surface gap spark plugs. Do I absolutely have to have a higher voltage ignition system in order to install and use surface gap plugs? My current ignition system is stock.

I've fired them with points in a 327 street car on LP Gas.