Guascor 7664604 / Siemens 7664653 ( old 7664765) and replacement pre-chamber for HGM560 and SFGM560 engines / GP2 & GP1

Guascor spark plug / Siemens spark plug

76.64.604 prechamber spark plugs available for Guascor HGM560 and SFGM560 gas engines. The new part number from 2019 was 7664765 (76.64.765) and traded under Siemens brand name however Siemens recently also changed the part number to 7664653 (76.64.653).

Guascor spark plug 76.64.604


This 7664GPH / 7664GP2 & 7664GP1 pre-chamber spark plug is specially designed for the Guascor HGM560 engines, but also can be used in the Guascor SFGM series. The unique design of this pre-chamber gives a better engine performance.  Other advantages of this exclusive spark plug are reduced (NOx) emissions, less blockage of the holes and longer plug life time which reduces maintenance and costs.

76.64.604 Guascor pre-chamber spark plug sleeve Guascor spark spark plug 7664604

These plugs were specially designed for Guascor HGM560 engines and can also be used in the Guascor SFGM series. The only requirement is the correct sleeve.


76.64.604 Guascor pre-chamber spark plug size


Unique technology based on producer's own patents

- Better engine performance thanks to a very efficient pre-chamber design
- Longer plug lifetime, reduces maintenance
- Lower gas consumption achievable
- Competitive pricing


Amplification of ignition energy level in main combustion chamber.

Fast and complete combustion process.

Reduced combustion pressure variations.

Improved engine efficiency.

Reduced NOx emission level.


Lower voltage requirement for the spark ignition.

High durability without maintenance.

Better engine performance due to lower wear rates.

The spark plug is produced in Austira therefore it represents the highest standard and reliability!


Spark plug user guideline

for GP2 & GP1 spark plugs (Guascor 7664604 / Siemens 7664653, 7664765)


Proper spark plug installation is very important to ensure optimal performance and safety on the engine. Please read these instructions carefully and always follow the instructions:


1./ Safety

Modem engine developments have led to more extreme engine running conditions, expressed in higher combustion pressures and temperatures. As a result of that, the latest ignition systems can provide higher ignition voltages and longer spark duration. This higher concentration of energy makes that nowadays a spark plug has to endure more severe conditions than ever before. Therefore, it is of the utmost importance to follow the guidelines below and the instructions that are provided by the engine manufacturer applicable when working around industrial engines.


These instructions should always be followed:

1.1./ Stay away from the spark plugs on a running engine

1.2./ Use the correct spark plug installation/removal tools

1.3./ Never over torque a sparkplug -to prevent damaging its construction

1.4./ Never under torque a spark plug – to prevent the plug from loosening

1.5./ Always use new spark plug gaskets to secure proper locking and sealing of the plug

1.6./ Never install spark plugs that have been dropped

1.7./ Keep spark plugs clean from grease or other contaminants during installation.


The installed spark plug type should be correctly chosen for the engine by either the engine- or spark plug manufacturer. Do not install different spark plugs if you are not certain that the plug is suitable for your engine application. Regularly check the physical con­dition of a spark plug to prevent premature failure.


2./ Installing spark plugs

Torque is one of the most critical aspects of spark plug installation. Torque directly affects the spark plugs' ability to transfer heat out of the combustion chamber.


A spark plug that is under-torqued will not be fully seated in the cylinder head; hence the heat transfer will be reduced. This will tend to elevate spark plug temperatures to unsafe levels, and pre-ignition and detonation will usually follow. Serious engine dama­ge is not far behind.


An over-torqued spark plug can suffer from severe stress to the metal shell which in turn can distort the spark plug's inner gas seals or even cause a hair­line fracture to the spark insulator, in either case, heat transfer can again be compromised and the above mentioned conditions can occur.


The cylinder head spark plug holes must always be cleaned and the good condition of the threads should be checked prior to installation, otherwise you may torqueing against dirt, debris or defective threads and the spark plug may actually end up under-torqued or improperly installed, even though your torque wrench says otherwise. Of course, you should only install spark plugs in a cool engine, because metal expands when it is hot, and installation may prove difficult. Proper torque specs for both aluminum and cast-iron cylinder heads are listed below.


Lubrication/ grease: Using grease is not recommended. However, if some anti-seize lubricant is used on the treads, then a small amount (pea size) should be spread uniformly on the clean threads and the specified installation torque should be reduced by approximately 10%. Also, if some dielectric grease is used on the ceramic insulator, then a small amount (pea size) should be spread uniformly after wiping clean the ceramic insulator with rubbing alcohol and a lint free cloth.


Spark PlugTorque

Spark plug type flat seat

Cylinder head steel

Cylinder head aluminum


30-38 Nm

28-36 Nm


40-45 Nm

44-48 Nm


3./ (Re)gapping

Passive pre-chamber spark plugs (PPC) cannot be regapped. If PPC plug stops performing it will need to be removed, using the correct removal tool and exchanged for a new plug.


4./ Tools and Maintenance

When re-installing a spark plug, always:

4.1./ Use a new spark plug gasket (see table).

4.2./ Remove dirt and debris from the threads and clean them dry.

4.3./ Remove dirt and debris from the ceramic insulator and wipe it dry

4.4./ In the case of PPC, check that the pre-chamber holes are free of dirt and debris. The cleaning of the pre-chamber holes should be such to prevent pushing any dirt or debris inside the pre-chamber (e.g. always hold the PPC vertically with the pre-chamber holes facing down)


5./ Warranty

Tue spark plug is warranted to be free of defects in manufacturing or materials as sold. It does not carry a service time warranty due to the uncertain nature of the application in which they are placed, and their normal operating service life may vary considerably per application. Damage due to non-conformance to the user guideline, physical abuse, exposu­re to excessive temperature or moisture conditions or misapplication is not covered by this warranty.


6./ Disclaimer

The spark plug manufacturer / supplier does not accept any responsibility for consequential damages from falling plugs in the engine, as a result of:

6.1./ Incorrect handling or improper installation of the spark plugs

6.2./ Uncontrolled (ignition / combustion) behavior of the engine

6.3./ Spark plug wear

6.4./ Any other impact including the quality of the product


Spark plug socket

Spark plug hex size

Socket part number

Socket length

M14 with 16.0 mm


6 cm

M14 with 16.0 mm


25 cm

M14 with 20.8 mm


6 cm

M18 with 20.8 mm


25 cm

M14 PPC, 6-teeth


12 cm

M18 with 22.2 mm


25 cm

Spark plug wrench, short version

10-60 NM, ½” square


40 cm


Spark plug hole conditioning tool

Spark plug thread size and reach

Tool part number


M14 – to 16 mm


later will be issued

M14 – over 16 mm


M18 – to 13 mm


M18 – over 16 mm



Spark plug gaskets

Thread size

Tool part number




Steel, zink plated



Steel, zink plated


Pre-chamber spark plug 71.018-02 to replace Guascor 76.64.604 / 7664604


Spark Plugs Replacement Guide

    1200rpm 1500rpm 1800rpm
FG/ FGLD natural gas 76.64.291     1250 IO-G-M-00-073 1000 IO-G-M-00-074
76.64.375     5000 4000
FG/ FGLD biogas (*) 76.64.292     1250 IO-G-M-00-073 1000 IO-G-M-00-074
76.64.375     5000 4000
SFGLD natural gas 76.64.375 4500 IO-G-M-00-067 3750 IO-G-M-00-065 3000 IO-G-M-00-066
SFGLD natural gas ISLAND 76.64.375 7500 IO-G-M-00-057 6000 IO-G-M-00-038 4500 IO-G-M-00-058
SFGLD natural gas PRIME 76.64.292         1000 IO-G-M-00-061
SFGLD natural gas STAND-BY 76.64.292         1000 IO-G-M-00-019
SFGLD biogas (*) 76.64.292 1250 IO-G-M-00-067 1000 IO-G-M-00-065 1000 IO-G-M-00-066
76.64.375 4500 3750 3000
SFGLD natural gas LCR 9,3:1 76.64.292 1250 IO-G-M-00-034 1000 IO-G-M-00-024 800 IO-G-M-00-035
76.64.375 5000 4000 3200
SFGLD natural gas LCR 8:1 76.64.292     2000 IO-G-M-00-024 1600 IO-G-M-00-035
SFGLD syngas (**) 76.64.292 800 IO-G-M-00-042 700 IO-G-M-00-003 600 IO-G-M-00-043
76.64.375 4000 3500 3000
SFGRD natural gas 76.64.292         1000 IO-G-M-00-062
SFGRD natural gas PRIME 76.64.292         1200 IO-G-M-00-063
SFGRD natural gas STAND-BY 76.64.292         1000 IO-G-M-00-064
HGM natural gas 76.64.604 3500 IO-G-M-00-072 3500 IO-G-M-00-070 3500 IO-G-M-00-071
HGM biogas 76.64.604 3500 IO-G-M-00-072 3500 IO-G-M-00-070 3500 IO-G-M-00-071
SFGM natural gas 76.64.685     3000 IO-G-M-00-068 3000 IO-G-M-00-069
SFGM natural gas ISLAND 76.64.685     4800 IO-G-M-00-051 4800 IO-G-M-00-059
SFGM biogas 76.64.685     3000 IO-G-M-00-068 3000 IO-G-M-00-069
SFGM propane 76.64.356     3000 IO-G-M-00-040 3000 IO-G-M-00-041
SFE ethanol 76.64.292         4800 IO-L-M-00-001

In case the engine is operating at variable speed always select your spark plugs in reference with the highest speed range.

(*) In case the variation of the LHV of the utilized biogas exeeds 10 per cent it is recommended to used 76.64.292 (S7664761) spark plugs.

(**) In case of very contaminated gas it is recommended to use 76.64.292 (S 76.64.761) spark plugs. 71.018-02


Verified 2022 January