C5 Spark Plug Gap (ignition experts help!)
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Joined: Oct 2020
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From: California
C5 Spark Plug Gap (ignition experts help!)
Hello,
I am curious to know if an improper spark plug gap will make my motor lose power (obviously yes, but how much off the ideal number)? Will changing/fixing the gap improve it? My car feels different, it feels a bit slower and wimpy. Don't get me wrong it still has power, but it feels different. I don't know maybe it's just me.
I have a 2003 Z06 with a stock bottom end, Katech Torquer cam (with supporting mods), ported heads, stock exhaust manifold, stock intake manifold, stock coil packs.
I am running NGK TR6GP plugs, gapped to .040 - .045. I do not remember the exact number because I changed them a while ago, but I believe I gapped them to either .040 or .042.
I will pull a plug and check the exact gap.
I'm also thinking about switching to th Ruthenium NGK TR5AHX Plugs.
-Frankie
I am curious to know if an improper spark plug gap will make my motor lose power (obviously yes, but how much off the ideal number)? Will changing/fixing the gap improve it? My car feels different, it feels a bit slower and wimpy. Don't get me wrong it still has power, but it feels different. I don't know maybe it's just me.
I have a 2003 Z06 with a stock bottom end, Katech Torquer cam (with supporting mods), ported heads, stock exhaust manifold, stock intake manifold, stock coil packs.
I am running NGK TR6GP plugs, gapped to .040 - .045. I do not remember the exact number because I changed them a while ago, but I believe I gapped them to either .040 or .042.
I will pull a plug and check the exact gap.
I'm also thinking about switching to th Ruthenium NGK TR5AHX Plugs.
-Frankie
Last edited by C5Frankie; Oct 8, 2021 at 08:07 PM.
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Joined: Jun 2020
Posts: 116
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From: Colorado Springs
Not sure on NGKs...
OEM Delco Platinum were 0.060 per fender sticker. Installed new Delco Iridium with specified gap of 0.040. Changed this year at 89K miles.
Hope that helps.
I did notice 0.5 mpg less, BUT at the same time I had injectors serviced by injector experts (https://cleaninginjector.com/) who found two of my injectors were 25% insufficient in flow.
With the plug and wire replacements and now balanced flow, I noticed an increase in throttle response but also noticed the sacrifice of 0.5 mpg in town on a nearly daily driver.
Perhaps its also now because I can put my foot in it more and feel the pep!
OEM Delco Platinum were 0.060 per fender sticker. Installed new Delco Iridium with specified gap of 0.040. Changed this year at 89K miles.
Hope that helps.
I did notice 0.5 mpg less, BUT at the same time I had injectors serviced by injector experts (https://cleaninginjector.com/) who found two of my injectors were 25% insufficient in flow.
With the plug and wire replacements and now balanced flow, I noticed an increase in throttle response but also noticed the sacrifice of 0.5 mpg in town on a nearly daily driver.
Perhaps its also now because I can put my foot in it more and feel the pep!
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I run NGK TR6 plugs gapped at .035, but I have a supercharger and that is a cooler plug specifically for supercharged engines.
For a NA engine your plug gap should be .040
For a NA engine your plug gap should be .040
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Hello,
I am curious to know if an improper spark plug gap will make my motor lose power (obviously yes, but how much off the ideal number)? Will changing/fixing the gap improve it? My car feels different, it feels a bit slower and wimpy. Don't get me wrong it still has power, but it feels different. I don't know maybe it's just me.
I have a 2003 Z06 with a stock bottom end, Katech Torquer cam (with supporting mods), ported heads, stock exhaust manifold, stock intake manifold, stock coil packs.
I am running NGK TR6GP plugs, gapped to .040 - .045. I do not remember the exact number because I changed them a while ago, but I believe I gapped them to either .040 or .042.
I will pull a plug and check the exact gap.
I'm also thinking about switching to th Ruthenium NGK TR5AHX Plugs.
-Frankie
I am curious to know if an improper spark plug gap will make my motor lose power (obviously yes, but how much off the ideal number)? Will changing/fixing the gap improve it? My car feels different, it feels a bit slower and wimpy. Don't get me wrong it still has power, but it feels different. I don't know maybe it's just me.
I have a 2003 Z06 with a stock bottom end, Katech Torquer cam (with supporting mods), ported heads, stock exhaust manifold, stock intake manifold, stock coil packs.
I am running NGK TR6GP plugs, gapped to .040 - .045. I do not remember the exact number because I changed them a while ago, but I believe I gapped them to either .040 or .042.
I will pull a plug and check the exact gap.
I'm also thinking about switching to th Ruthenium NGK TR5AHX Plugs.
-Frankie
Majority of people here are stock setup anyways so most likely your gonna get stock specs
Last edited by My Vette Life; Oct 9, 2021 at 04:09 PM.
Drifting
Joined: Sep 2009
Posts: 1,862
Likes: 594
From: Prescott, Arizona
From the factory, many C5's had spark plugs gapped at 0.60. Later the factory changed the recommended gap to 0.40. My 2001 FSM says the gap should be 0.60.
When I changed plugs at about 77,000 miles on the car circa 2010, the original plugs did indeed have a very wide gap, around 0.060, but the new plugs I installed were gapped by the manufacturer at 0.40.
I noticed no difference in performance of the car.
43,000 miles, 11 years and 22 track days later.
When I changed plugs at about 77,000 miles on the car circa 2010, the original plugs did indeed have a very wide gap, around 0.060, but the new plugs I installed were gapped by the manufacturer at 0.40.
I noticed no difference in performance of the car.
43,000 miles, 11 years and 22 track days later.
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GM originally recommended .060 gap however several years ago they changed it to .040
A TR5 is pre gapped at .040 and a TR55 is pre gapped at .060
ALSO I would only use a TR6 plug on a boosted application--It is way to cold for a daily driver N/A engine even with a cam---Fouling can occur with such a cold plug as a TR6
You may have other issues Is it mis-firing ??? Check your wires as well----
If you are losing power it may be to "false knock " which occurs with large cams and LT headers
The knock sensors hear the new noises from the cam and thin walled LT's and interpret that noise as pinging- Very common to lose 4-5* of timing with false knock and will will hear No pinging either These engine only run about 25* at WOT and if you lose 5* that is huge
Data logging the knock retard is the only way to know for sure to see what's going on---
The fix is to have a tuner "desensitize " your knock tables to get rid of the false knock
Where are you buying your gas ???? make sure to only buy good gas from a popular station that always has fresh fuel Bad gas is sometimes the simplest reason for false Knock
A TR5 is pre gapped at .040 and a TR55 is pre gapped at .060
ALSO I would only use a TR6 plug on a boosted application--It is way to cold for a daily driver N/A engine even with a cam---Fouling can occur with such a cold plug as a TR6
You may have other issues Is it mis-firing ??? Check your wires as well----
If you are losing power it may be to "false knock " which occurs with large cams and LT headers
The knock sensors hear the new noises from the cam and thin walled LT's and interpret that noise as pinging- Very common to lose 4-5* of timing with false knock and will will hear No pinging either These engine only run about 25* at WOT and if you lose 5* that is huge
Data logging the knock retard is the only way to know for sure to see what's going on---
The fix is to have a tuner "desensitize " your knock tables to get rid of the false knock
Where are you buying your gas ???? make sure to only buy good gas from a popular station that always has fresh fuel Bad gas is sometimes the simplest reason for false Knock