EMHART TEKNOLOGIES • 50 Shelton Technology Center, Shelton, CT 06484 • Tel. 877-EMHART-1 • Fax: 800-225-5614 • emhart.com

Serrated Spark PlugInserts

Technical Bulletin 804C

emhart.com

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Technical Bulletin 804C

SERRATEDSPARK PLUG INSERTS(FOR ORIGINAL DESIGN AND PRODUCTION SALVAGE IN INDUSTRIAL ENGINES)

— WHAT THEY ARE…Heli-Coil Spark Plug Inserts are manufactured from 18-8 round stainless steel wire that is formed into a 60° diamond-shaped wire. This cold-worked wire, which has a tensile strength of 200,000 PSI, is wound into a spiral coil with a drivingtang and a notch to remove the tang after the insert is screwed into the Heli-Coil tapped hole.

RETENTION PRINCIPLEIn its free state the insert is larger in diameter than the tapped hole. Once installed, the insert assumes the configuration ofthe tapped hole. The resultant outward spring-like action anchors the insert in place.

In addition, the Spark Plug Insert has a serrated top coil which is offset into the parent material. This offsetting isrecommended because of the high temperature and high performance requirements of spark plug ports.The Heli-Coil SparkPlug Insert becomes an integral part of the cylinder head – providing high strength threads which exceed in surfacesmoothness, hardness and accuracy any threads that can be tapped in any material.

– WHAT THEY DO …n Permit easier spark plug removal because there is no possibility of corrosion between the spark plug and the hard

drawn, smooth surface stainless steel Heli-Coil Insert.

n Eliminate thread failure due to stripping, vibration and fatigue.

n Assure freedom from thread wear, even after repeated disassembly and reassembly.

n Greatly increase tapped thread strength under all operating conditions.

n Offer speed and economy in production salvage, providing greater-than-original thread strength.

– HOW THEY ARE USED …The design of a Heli-Coil Spark Plug Assembly follows conventional engineering practice.

Select the correct Heli-Coil Insert based on the plug length. In the event that a special plug length is being used, ourApplications Department should be consulted for a suitable Heli-Coil Insert.

AIRCRAFT ENGINESOriginal Equipment and Production SalvageUse the same basic procedure described on Page 2 when making installations in aircraft engines. However, because ofspecial engine performance requirements, location of spark plug ports, etc., special tools and additional procedures may berequired. Our Applications Dept. should be consulted for original equipment applications in aircraft engines.

RepairRepairs to damaged spark plug ports on aircraft engines should be made in accordance with the following:

Manufacturer’s Service Bulletin for each specific engine.

AF T.O. 44H1-117 (NAVWEPS 02-1-19).

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SIZE

: 14-

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SIZE

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Emhart TeknologiesCustomer Service50 Shelton Technology CenterP.O.Box 859Shelton, CT 06484 USATel. (877) EMHART-1Tel. (877) 364-2781Fax. (800) 225-5614

© 2011 Emhart Teknologies emhart.com HC804C (06/11)

Heli-Coil® is a registered trademark of Emhart Teknologies.

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