GT350 spark plug gap spec revised for 2019?

[rspec99]

I decided to pull my spark plugs out for inspection on my 2016 GT350. There was no spec quoted in the owner's manual or the supplement. When I measured my gaps, they were in the .050" range, which is about what the 5.0's spec is. Otherwise, the plugs seemed to read well as in dry, brownish/black, with no deposits. I am running oil separators, and my engine doesn't burn oil.

However, when I checked the 2019 GT350 owner's supplement, it states .035"-.039" for the spark plug gap spec. I replaced my stock plugs with NGK's and decided to gap them to the .037". Prior to replacing the plugs, my car would occasionally have a miss or hiccup at idle. After the new plugs and smaller plug gap, it idles smoothly and no miss. There is no other perceptible change in drivability or performance.

Just curious about others in the communities experience.

Sponsored

 

[Shift]

My 2016 engine did "hiccup" at idle, the new replacement 2019 engine, not so much.

 

[ZX3ST]

Interesting.

My 2018 Shelby supplement doesn't mention plug gap, but they do list SP-519 / CYFS-12Y as the replacement part (apparently SP-519 has since been replaced by SP-548). My google-fu tells me those plugs are intended to be gapped 0.049-0.053.

I wonder if that's a typo in the manual. 0.035-0.039 sounds to me a bit tight for N/A, and more appropriate for a F/I motor.

Which NGK part did you use?

 

[rspec99]

Agreed. That range seems more appropriate for a forced induction car. The new 2020 GT500 spark plug gap stated in the owner's supplement is .037"

If it is a typo, it's in the 2020 GT350 owner's supplement as well. Does anyone know a Ford tech or have access to the workshop manuals for the 2019+ GT350's?

 

[honeybadger]

FWIW - I've been using these per a recommendation from a gent that did a bunch of the testing for Ford when they were developing the Voodoo. They're 1 step colder than the OEM stuff. He recommended them for heavy track use. I ran 1 set of OEM plugs and then 1 set of these so far and have been more impressed with these than OEM.

NGK (6510) LTR7IX-11 Iridium IX Spark Plug

https://www.amazon.com/gp/product/B001RLTZ7A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[ZX3ST]

@honeybadger Are you running those at out-of-box gap?

Another data point here - Those are pre-gapped at 0.044 according to NGK.

 

[honeybadger]

@honeybadger Are you running those at out-of-box gap?

Another data point here - Those are pre-gapped at 0.044 according to NGK.

Yep. I was told to leave the gaps alone. They've been great and were consistent out the box when I measured them. Actually about to pick another set up for this weekend.

 

[SVTinAR]

Hadn't thought of that but a wide plug gap like that would seem a likely cause of that random, rare hiccup at idle. I had one of them yesterday on the way to work at a stop light. I know when I experimented with a wide plug gap on an transistorized ignition system in my 66 Corvette, that it seemed to have a similar random miss at idle until I set them closer to stock.

 

[JAJ]

Hadn't thought of that but a wide plug gap like that would seem a likely cause of that random, rare hiccup at idle. I had one of them yesterday on the way to work at a stop light. I know when I experimented with a wide plug gap on an transistorized ignition system in my 66 Corvette, that it seemed to have a similar random miss at idle until I set them closer to stock.

Going back to the OP question, the 2019 gap is indeed smaller than the spec for the 2016 (and probably through 2018). The 2016 service manual says 1.25 to 1.35 mm gap, and the 2019 gap in the Owner's Supplement above is from 0.9 to 1.0 mm.

BTW, for anyone interested in the NGK plugs that @honeybadger listed, the USA NGK site doesn't provide any technical information, but the Australia site does. According to the NGK part finder, the NGK OEM-spec replacement spark plug for the Voodoo is LTR6DP13, a platinum-tip heat-range 6 plug gapped at 1.3 mm. They recommend stepping up to an iridium-tipped LTR6IX-11, also a heat-range 6 plug. The next colder heat-range iridium plug is the LTR7IX-11 that HB is using. The "6" or "7" in the part number is the heat range (higher is colder) and the "11" indicates the factory-set gap of 1.1 mm.

 

[NoXiDe]

@JAJ, what do you use?

 

[JAJ]

@JAJ, what do you use?

My car still has the factory plugs. There's been no reason to change them so far.

 

[Balatgek1]

I decided to pull my spark plugs out for inspection on my 2016 GT350. There was no spec quoted in the owner's manual or the supplement. When I measured my gaps, they were in the .050" range, which is about what the 5.0's spec is. Otherwise, the plugs seemed to read well as in dry, brownish/black, with no deposits. I am running oil separators, and my engine doesn't burn oil.

However, when I checked the 2019 GT350 owner's supplement, it states .035"-.039" for the spark plug gap spec. I replaced my stock plugs with NGK's and decided to gap them to the .037". Prior to replacing the plugs, my car would occasionally have a miss or hiccup at idle. After the new plugs and smaller plug gap, it idles smoothly and no miss. There is no other perceptible change in drivability or performance.

Just curious about others in the communities experience.

Just talked to Ken at Ford Performance, after some research he said that for my 2019 Shelby GT350, the Motorcraft CYFS-12F-1X is the Spark Plug and Gap is 0.035- 0.039.
Well, when I pulled the plugs, they were all between 0.052 and 0.053 from the factory. Is it possible they opened up that much in 20K miles? Tried .038 and .052 gap (with the .038 gap I lost some fuel mileage) The new plugs or gap didn't solve my slight idle miss/hiccup issue. Dealer thinks something in the EVAP system. As far as the plug gap goes,

who knows, the manual and Ford Performance says one thing and the original plugs say different.

 

[galaxy]

So is this narrower gap retroactive for earlier years? Doesn't make any sense that the gap would be updated for newer engines and then pre '19 still using the larger gap.

NGK still lists the LTR6IX-11 at .052".

On a stock engine that's not tracked, is there a reason or benefit to go with that one step colder?

 

[galaxy]

Jump starting this thread becuase I ran across this extra little tid-bit of info doing spark plug homework (and never find an answer or guidance to the narrower gap being retro to the 15-18 years)...

For the stock heat range (6) NGK plugs, there's an additional part number. NGK has a 6509 and a 94374. Both of these part numbers are LTR6IX plugs -- confirmend with NGK they are identical. The only difference is the preset factory gap. The 6509 out of the box with .052" and the 94374 out of the box with a .032". Just a little bit of an add-on to the info @JAJ provided a few posts up.

Based on the new recommended gap, I suppose it's a coin toss between the two? Either need to open the gap on one, or close a little on the other? Thoughts?

Still debating on going with the prevously recommended 6510 (one step colder - 7) in the same plug for the tune. Lot's of 50/50 split recommendations between the heat ranges out there.

 

[WItoTX]

Based on this thread, and another one, I kept mine at .35-.39. Next set I'll go one step colder and keep the same gap, but try to keep everything closer to .35. The plan is a new set every track season.

I found two plugs out of spec when I pulled them (likely had never been replaced). Unsurprisingly, they were cyl 4 and 8. But timing looked great on all the plugs. For reference, I'm on a stock tune. I also had an ever so slight hiccup that went away with new plugs.

Sponsored