Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Workshop Note - Roadster S1 Spark Plug Inspection

Changed the 3 easy spark plugs today. Was surprised at the gap of those that came out. 1.30mm, 1.15mm and 0.83mm. No apparent difference in the idle on start up, still a bit of an occasional hunt. Will see how it feels once I've replaced the other side.

Unusual. Makes you wonder if the 0.83mm one was a replacement in more recent times.( I am guessing thats around the recommended setting. ) Did it look the same sort of age and make as the others?

Interesting point Deejay. I've now replaced the difficult ones. The left 3 are from the one side and have an orange staining on the ceramic. These were the. First lot in removed with the inconsistent gap. The right 3 were from the other side, do not have the staining, and had a more consistent gap (1.30, 1.27 and 1.23). They are all the same brand are in generally a good condition.

They've been changed at least once as originals would be FoMoCo

The ones above don't appear to have the very fine Iridium tip ??

No, just standard. I bought some platinum iridium hybrid one s off ebay, so maybe I'll see a difference when I next go for a spin. Checking my file, the one but last service before I bought it just cleaned them up. The service schedule for the engine recommends replacing after 60k miles, but from what I've read, quality plugs improve performance, fuel economy and emissions, so for the cost of a new set of decent plugs, it would make sense just to replace them rather than just giving them a clean.

So as a matter of interest, what is the correct gap for these engines…Online, I have seen 1.25-1.35mm for 3.7 v6 engines, but only 0.83mm for 3.0 v6 ?

Back on the day 25 thou or 0.6mm was standard plug gap and old style NGK 14mm plugs still come pre-set to this. Nowadays with modern individual coil packs they seem to have crept up to 35 thou or around 0.8mm. Since the gap will increase if anything with age (particularly with fine tip plugs) I still aim for the lower end if in doubt.

Thanks for that Richard; it confirms my original thoughts. Would have thought the 1.25mm figures would be more akin to a race spec engine possibly.

Don’t know if this helps but for the Focus Sigma engine I found information on the web that suggested the original gap specification was 1.25 to 1.35mm. This was then apparently reduced due to straining and failing the coil packs and 1.2mm is suggested. The original FoMoCo plugs that came out of my 4/4 were gapped at 1.2mm. NGK TR5B-13 are gapped at 1.3 out of the box and their suggested upgrade plug, LTR51X-11, is 1.1mm as the part numbers indicate. I fitted the upgrade Iridium’s straight out out of the box and they seem fine. Please don’t take this as gospel of course, usual disclaimer that you check this is correct etc.

The OE plugs that Ford fit are the fine tip Iridium, so you could currently be running on the wrong plugs, and the gap is WAY too big