sdpatt
Sr. SHO Engr.
I had read topics in this Forum previously about owners who thought they could improve the performance of their SHO engine by increasing the gap on the spark plugs to a larger than specified value. I replied to some of those topics with posts that the .042"-.046" gap range was specified for a reason: to provide the best combustion to provide the greatest power and efficiency.
The engine in my SHO is getting close to its sixth, yes, I said sixth, 60K service as it rolls over 318,500 miles. The last complete 60K was performed at 268,000 miles and I was planning for the next service at around 330,000 miles. At the current rate of 500+ miles a week, I was going to need a free weekend around Thanksgiving or Christmas.
Just to see how the plugs were looking, I pulled the boot off of cylinder #4. There was a small, but still disappointing amount of oil at the bottom of the plug well. Disappointing because I had replaced the valve cover and plug well seals at the last service. I removed the plug to check the gap. The insulator looked clean and light gray, but the gap looked a little big. The feeler gauge found .065" between the electrodes. I have always used the OEM AGSP32PP Motorcraft plugs and I have never seen that large of a gap before even after a full 60,000 miles.
I was short on time and checked the front bank plugs and the #1 plug that could be accessed with removing only the vacuum line. Plugs 4, 5 and 6 all had gaps in the range of .060"-.065". The #1 plug was still on the money at .045" after the original .042" setting at the time of installation. I suspect that the use of cheaper 89 octane fuel and the accompanying noticeable pinging may have had some effect on the plugs.
Starting the engine after resetting the four plug gaps revealed that the engine could tell the difference. She was running more smoothly and more evenly at idle and with less vibration at 2,000-4,000 as I turned the throttle by hand. On the road, the surging I had been feeling at 1,500-2,000 at light throttle was gone, replaced by a smooth pull. I covered 120 miles today after filling the gas tank last night. The fuel gauge was still pointing at the 7/8 mark. I usually get no more than about 100 miles by that point even with steady highway cruising.
The drive to work today was mostly highway, but with some very spirited motoring to make my way thorugh traffic. The GPS revealed a max speed of 92.2 mph. Yeah, I baby my SHO. That's how I got it to over 300,000 miles. Riiiigggghhhhht. I look forward to the 60K service to make sure the SHO is running at her best. The moral of the story: gap those plugs to the specified range of .042"-.046" - it will make you and your engine happy.
The engine in my SHO is getting close to its sixth, yes, I said sixth, 60K service as it rolls over 318,500 miles. The last complete 60K was performed at 268,000 miles and I was planning for the next service at around 330,000 miles. At the current rate of 500+ miles a week, I was going to need a free weekend around Thanksgiving or Christmas.
Just to see how the plugs were looking, I pulled the boot off of cylinder #4. There was a small, but still disappointing amount of oil at the bottom of the plug well. Disappointing because I had replaced the valve cover and plug well seals at the last service. I removed the plug to check the gap. The insulator looked clean and light gray, but the gap looked a little big. The feeler gauge found .065" between the electrodes. I have always used the OEM AGSP32PP Motorcraft plugs and I have never seen that large of a gap before even after a full 60,000 miles.
I was short on time and checked the front bank plugs and the #1 plug that could be accessed with removing only the vacuum line. Plugs 4, 5 and 6 all had gaps in the range of .060"-.065". The #1 plug was still on the money at .045" after the original .042" setting at the time of installation. I suspect that the use of cheaper 89 octane fuel and the accompanying noticeable pinging may have had some effect on the plugs.
Starting the engine after resetting the four plug gaps revealed that the engine could tell the difference. She was running more smoothly and more evenly at idle and with less vibration at 2,000-4,000 as I turned the throttle by hand. On the road, the surging I had been feeling at 1,500-2,000 at light throttle was gone, replaced by a smooth pull. I covered 120 miles today after filling the gas tank last night. The fuel gauge was still pointing at the 7/8 mark. I usually get no more than about 100 miles by that point even with steady highway cruising.
The drive to work today was mostly highway, but with some very spirited motoring to make my way thorugh traffic. The GPS revealed a max speed of 92.2 mph. Yeah, I baby my SHO. That's how I got it to over 300,000 miles. Riiiigggghhhhht. I look forward to the 60K service to make sure the SHO is running at her best. The moral of the story: gap those plugs to the specified range of .042"-.046" - it will make you and your engine happy.
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