I was looking at my 2003 Owner's Manual regarding the spark plug gap. This is what it states:

So...my question...when gapping the spark plugs before installing them, what do you use??? Does it matter really???

.052"?
.054"? <-- I'm thinking here right???
.056"?

See...my '76 390FE uses the .044" gap. Not a somewhere in between gap...

Thanks,

biz

 

Gaps get increasingly wider with age and wear

the tendency these days to list a span like you see 52 thou to 56 thou is so a tech trouble shooting can determine if the gap is too wide and needs adjusted or ignored as the fault

I always use the lower number, in this case 52 thou for my street cars.... when setting up for high performance I try to use the widest gap that stays stable... easy on a 2 cylinder motor cycle and too much pain in a V10 to screw with Grin

 

Biz, I gapped mine at .054" when I did them a few months back. The NAPA that I deal w/ on a regular basis told me that the gap was .054". I'm not going to say that it was right or by the book or anything, but it's what I was told and it's what I went with. It worked just fine for me. So far, so good. I'm sure if I'm wrong, I'll be told.....

Dave

 

Appreciate the replies!

So...I understand the thinking behind Fredvon4 post. Gap the spark plug at the closest recommended setting, so that over the 99,000 miles before doing a spark plug change the gap will widen, but in theory stay in the .056" max gap range. Makes sense!

However, with a wider gap...should provide a better burn. Right? So maybe the .054" is the best way to go, if the spark plugs will be changed sooner than later.

Any more opinions/facts here V10'ers???

biz

 

With the COP design and a low compression motor you can probably get away with a 60 thousandths gap, and still have a stable arc that won't "blow out" and cause misfires... generally speaking the "Hotter" the spark arc the more consistent the timing and fuel burn will be. But there is always a trade off and our fuels are not very precise.

You will not measure much if any difference on a dyno between a 0.045 to 0.060 gap on a stock tuned v10 motor

Indexed plugs, widest stable gap, and more aggressive ignition curve can probably get 5 to 15 more HP out of her... not worth the troubel for a stock tow haul machine

Use what ever gap you want and you can do with out having to stack feeler gage segments together. ( don't like "wire" type plug gap tools and only use fan out shim style feeler gages...being traind for decades on them is why... use what you know and you are good with)

0.054 is appropriate for 30-60 thousand mile planned plug changes but probably too wide for a forget about it 120,000 mile lazy person.

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The rest of this note is a rehash of crap I have posted over the years

Just some thoughts and observations from the last 10 versions of 2 and 3 valve V10s I have owned or screwed with

Those who know me can probably skip this
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When I changed the factory plugs on the 2001 2v V10 at 20,000 miles (blow out concern) I had a new set of MotorCraft with me. The factory plugs all were near perfect and gap only widened just a tad looser then 0.052.... I did not have a 0.053 and 0.054 was too tight. I set the new plugs to 0.052 and never gave it a thought. That truck got assassinated by me so I never got to follow their wear on my next planned re-plug at 50,000. But I did plan to do re-plugging every 30,000 based on amount of corrosion and deterioration of the plugs and COP "boots".

................(I also found a crack in one of the COPs so I looked at all ten under a 4 power lighted magnifier and saw many tiny cracks in the potting mixture that seals the units. I decided that getting water on a HOT COP would not be a good idea so I changed the way I "wash" this motor. Always, outside air temp cold motor, and never with any water pressure. Just hose end trickle to "flood" off the simple green soap I use, then a good dousing with a lot of WD 40, then a blow off with compressed air, then start for a normal operating temp dry out)

My 05 has 30K on her this week and I checked the plug torque at 5 thousand without removing any of the plugs... I simply recorded the "break away" Torque (175 inch pounds), loosened one full turn, and re-torqued to 165 inch pounds.

On the 01 at 20,000 miles I found three loose plugs. Any way, they were much too loose for my comfort being that I was not able to read the break away torque because the plug simply was that loose... probably could have removed it with my fingers if I could have got on to it good. And that experience was repeated on all 8 or our service company's small fleet of v10 powered trucks... each one had too loose plugs from the factory and one had a plug that I thought was going to twist off in the head...Lots of rust corrosion on that one plug from a coolant leak.


Final thought in case a few here doing a re-plug and have not read all of the good advice in this forum on the proceedure... you MUST blow out all the sand, rust, dirt and crap that IS down in each plug hole before you loosen the plug, then you must blow it out again before removing the plug...and you need all the other plug holes to have a plug in them when you do this tedious task...

This motor traps a LOT of crap in the plug recesses and if you just pull the plug much of it will fall into the cylinder and score the walls and make the ring seal fail or be real weak...

I would never let 80% of the service center and factory trained techs I know do this job...they are too much under the gun for time and will bypass this step most of the time

 

I agree here....... I used the number in the middle for the gap when I replaced my plugs, and very important is that recess that holds in all of that dirt. I used an air compressor with a basketball needle inflator tip to blow out all of that junk. And EVERY one had stuff in it! If I didn't learn that tip here on FTE, I would have probably just yanked them and all of that dirt would have fallen into the motor.