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Old 02-14-2018, 12:02 AM
mw85gt mw85gt is offline
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Default 3 spark plug electrodes MIA

We put new plugs in the car hours before the Runoffs at Indy.
After the race, the plugs in cylinders 1, 3, and 8 were missing their electrodes.
The electrodes don't look melted, they appear to be fractured.
We were running NGK R5671A-9 plugs.
I am thinking about going with a cold surface gap style plug?
Suggestions gratefully accepted.
Thank you
Mark
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Last edited by mw85gt; 02-14-2018 at 12:08 AM. Reason: forgot important details
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  #2  
Old 02-14-2018, 07:52 AM
Ken Felice Ken Felice is offline
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Default spark plugs

Very common in the Ford engines. Ford has a harmonic that the rest of the engines don't have. We have talked to many plug manufactures they all say the same thing. A surface gap plug will stop this but you may have to put a little more timing in it. Hope this helps
Ken Felice
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Old 02-14-2018, 08:09 AM
Scott Sanda Scott Sanda is offline
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Have you checked seated plug to piston clearance? I donít know your geometry, or if itís even a worry on your car, but on my GTR I need to run spark plug spacers, if I do not, the electrodes and the pistons get biblical.
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Old 02-14-2018, 11:20 AM
fast2rev fast2rev is offline
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it appears the piston is hitting the electrode, make sure you have the right length plug for your type head, measure your piston to head clearance, you can remove the head and use clay or with the head on make a clay worm insert it in the sparkplug hole and rotate the motor by hand and measure the thickness, note which direction the electrode is pointing in the cylinders that did not break, shims are available to put on the plug to change the depth and locate the electrode to face your intake valve
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Old 02-14-2018, 11:52 AM
andy mcdermid andy mcdermid is offline
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The spark plugs break due to harmonics, clearance is not the issue. change you plug on a regulator basis. Same problem with us. I replace the plugs every other weekend.


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Old 02-14-2018, 04:35 PM
mw85gt mw85gt is offline
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Default 3 electrodes MIA

Appreciate the feedback from everyone, thank you
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