View Full Version : plug gaps?

08-11-2002, 11:38 AM
I'm in the middle of putting p&p heads and intake on my 91 SC 5-speed. The only other mod is a flowmaster force II exhaust with test pipes in place of the cats. I can not find the gap specs in my Haynes manual. Any input would be greatly appriciated.


08-11-2002, 12:57 PM
I have had good luck with gapping autolite or motorcraft double platinum stock spec plugs at .048. I use autolite pro-fit or motorcraft wires exclusively. I am yet to misfire under boost and I have had my car with a virtually identical setup to yours so I don't see why it shouldn't work for you. A few guys have tried running a colder plug (late model 3.8 stang) something you may want to check into, I haven't tried it and really don't like giving advice unless I have personal experience.

Adam Mullen
The SC Kid

08-11-2002, 04:30 PM
I have motorcraft 32PP at .047

08-11-2002, 06:32 PM
I just got a set of Iridium plugs today, cool looking plugs. but they say DO NOT GAP on them, the electrode is very pencil thin so I see why they say not to GAP them, so I assume they take great care in making sure the gaps are all equal, I also ammuse they will be the stock gap, I have yet to open the package and check the gap on them.

Be interesting to see how they work, I have heard good things so far.

David Neibert
08-11-2002, 11:02 PM
Iridium plugs are great, however I re-gapped mine to .030. I only read the instructions when I get stuck.


08-11-2002, 11:54 PM
hehe so you re-gapped the Iridium pugs? Cool, maybe I'll try that later but so far the car seems to run fine so I'll leave them for now.

08-12-2002, 03:15 AM
I regapped mine as well..Put them in my 90 Izuz trooper and my 2001 Aprilia Mille R..I also did not read directions hehe,,But remeber...SO long as teh plug still fires...Teh wider the gap the more power..And Iridium supposedly gives off a hotter spark..Which in turn would allow you all things being equal a larger gap over a platinum plug..Me..I just got mine in for my SC ...colder plug..There goin in as is..One thing I didnt understand....Denso has 2 plug numbers for a 94 tbird with a v6..One for SC..one naturally asp....Im assuming the SC ones are the colder plug..BUT...The standard v6 plug was the same # as the 4.6 v8 plug..So the naturally aspirated motors used a colder plug?????...I need to look into that a little better...haha..Maybe I have my plug numbers backwards:O)~

David Neibert
08-12-2002, 10:53 AM
The only reason we put the Iridium plugs in mine was because the dyno operator (mustang speed shop) said my spark was blowing out. He said they had good luck using the Iridiums gapped to .030 on the supercharged mustangs.

It turned out to be some broken inner valve springs (9) that allowed the valves to float at 5200 rpms. We pulled the plugs after about 2000 miles (leaking HG) and they looked great. A little sooty but white at the electrode. We pulled them again recently trying to track down a hard starting problem and they still looked brand new.


08-12-2002, 12:30 PM
my plugs(double platinums) are gapped at .50, is this ok, I just put them in with new plug wires (motorcraft) to see if that was why the car is running so poorly. It didn't help, so next is the cam sensor because my tach is jumping around. Hopefully that does it.

Rob Noth
08-12-2002, 02:08 PM
I have the NGK iridium plugs (TR55-IX) and they also said not to regap, but the stock gap was huge, something like .066-.068. So I regapped them (very carefully) to .054 and everything has been fine.


08-12-2002, 10:46 PM
Rob, those are the same plugs I got and I checked the gap on all of them, they were all 0.54 or 0.55, so almost perfect so I left them alone, they seem to run fien so far.