• Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

spark plug gap for headswapped cars

  • Thread starter Thread starter RysRed96GT
  • Start date Start date Nov 13, 2004
Prev
  • 1
  • 2
  • 3
First Prev 3 of 3

tomustang

Psychotic Member
Founding Member
Jun 8, 2000
3,434
2
78
McLean Hospital
Nov 27, 2005
#41
  • Nov 27, 2005
  • #41
mrvax said:
My personal experience is that .035 is NO FREEGIN GOOD for a N/A Stang. When I gapped the plugs to the factory setting, the car ran MUCH better. I'm sticking with .053-.057.
Click to expand...
See when I done the swap with the stock gap I didn't feel any difference in power at all, didn't even notice anything. After I tried .40 I was sold and felt the gain.
 

CobraM23

Founding Member
Oct 16, 2002
266
1
16
Johnson City, TN
Nov 27, 2005
#42
  • Nov 27, 2005
  • #42
At first I had TR-55's in at .054 and I had detonation and missing every once in awhile. I gapped them down to .035 and the car runs a hell of a lot better, no detonation at WOT or missing to be heard of. It does ping going up a hill in OD but thats to be expected. My car runs better with the smaller gap.
 

tomustang

Psychotic Member
Founding Member
Jun 8, 2000
3,434
2
78
McLean Hospital
Nov 27, 2005
#43
  • Nov 27, 2005
  • #43
CobraM23 said:
At first I had TR-55's in at .054 and I had detonation and missing every once in awhile. I gapped them down to .035 and the car runs a hell of a lot better, no detonation at WOT or missing to be heard of. It does ping going up a hill in OD but thats to be expected. My car runs better with the smaller gap.
Click to expand...
What gas?
 

mrvax

Stay thirsty my friends
Founding Member
Nov 29, 1999
5,225
3
79
SN Moderator: Orlando, Fl.
Nov 27, 2005
#44
  • Nov 27, 2005
  • #44
tomustang said:
See when I done the swap with the stock gap I didn't feel any difference in power at all, didn't even notice anything. After I tried .40 I was sold and felt the gain.
Click to expand...

Are you saying you did the PI swap, gapped the plugs to factory specs and did not feel gains from the swap???
 

RysRed96GT

I like it FURRY!!!
Founding Member
Apr 9, 2001
3,207
0
56
Pasadena, MD
Nov 27, 2005
#45
  • Nov 27, 2005
  • #45
i at least recall for mine that it was smoother going from the .054 gap to .040. my current plugs, though they're a year old, are gapped to .040 and the engine purrs.
 

tomustang

Psychotic Member
Founding Member
Jun 8, 2000
3,434
2
78
McLean Hospital
Nov 27, 2005
#46
  • Nov 27, 2005
  • #46
mrvax said:
Are you saying you did the PI swap, gapped the plugs to factory specs and did not feel gains from the swap???
Click to expand...
Well the stock plugs were gapped to factory specs when I bought them
 

CobraM23

Founding Member
Oct 16, 2002
266
1
16
Johnson City, TN
Nov 28, 2005
#47
  • Nov 28, 2005
  • #47
tomustang said:
What gas?
Click to expand...

93
 

mrvax

Stay thirsty my friends
Founding Member
Nov 29, 1999
5,225
3
79
SN Moderator: Orlando, Fl.
Nov 28, 2005
#48
  • Nov 28, 2005
  • #48
tomustang said:
Well the stock plugs were gapped to factory specs when I bought them
Click to expand...


Yes but what I'm asking is are you saying you did the headswap and felt no gains until you gapped the plugs to .040?
 

tomustang

Psychotic Member
Founding Member
Jun 8, 2000
3,434
2
78
McLean Hospital
Nov 28, 2005
#49
  • Nov 28, 2005
  • #49
mrvax said:
Yes but what I'm asking is are you saying you did the headswap and felt no gains until you gapped the plugs to .040?
Click to expand...
Yes, It was more like a struggle feeling than a gain,
 

mrvax

Stay thirsty my friends
Founding Member
Nov 29, 1999
5,225
3
79
SN Moderator: Orlando, Fl.
Nov 28, 2005
#50
  • Nov 28, 2005
  • #50
This whole thing with the smaller gap doesn't make sence to me. You'd think that by having the larger gap, there would be a slightly longer burn time, much like the MSD (multi-spark-discharge) product. A short gap would have a quick burn.

Provided of course that you had enough voltage to carry the spark across the larger gap just seems like it would work better. I know it did in my case but I'm surprised by the people who say they felt .040 was better.
 
B

billyfe390

New Member
Aug 18, 2003
573
0
0
Nov 28, 2005
#51
  • Nov 28, 2005
  • #51
If you felt a gain by reducing the gap you have weak coils or bad plug wires.

If its NA you make the most power with the widest gap.
 

tomustang

Psychotic Member
Founding Member
Jun 8, 2000
3,434
2
78
McLean Hospital
Nov 28, 2005
#52
  • Nov 28, 2005
  • #52
mrvax said:
This whole thing with the smaller gap doesn't make sence to me. You'd think that by having the larger gap, there would be a slightly longer burn time, much like the MSD (multi-spark-discharge) product. A short gap would have a quick burn.

Provided of course that you had enough voltage to carry the spark across the larger gap just seems like it would work better. I know it did in my case but I'm surprised by the people who say they felt .040 was better.
Click to expand...
Higher compression runs better with a smaller gap 9.0:1 to 10.3-5:1

Something many do not know, is that with Higher Compression ratios and Superchargers as well as Nitrous, in many cases smaller spark plug gaps must be used as well as the use of a much hotter ignition system (see above). These higher cylinder pressures require more energy to jump the spark plug gap.
Click to expand...
http://www.centuryperformance.com/spark.asp

3. Gapping

Since the gap size has a direct affect on the spark plug's tip temperature and on the voltage necessary to ionise (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.
Click to expand...
http://www.ngkspark.com.au/tech_index.htm?http://www.ngkspark.com.au/pages/tech_content.htm

billyfe390 said:
If you felt a gain by reducing the gap you have weak coils or bad plug wires.
Click to expand...
That is also true.
 

DropTopPony

Noob Slayer
Founding Member
Aug 13, 2002
2,570
3
48
south jersey
Nov 28, 2005
#53
  • Nov 28, 2005
  • #53
My denso's are gapped at .055 but i do have Screamon Deamon coil packs and livewires for a hotter spark. That is what they suggested with denso plugs...Runs smooth.
 

CanadaStang

New Member
Sep 7, 2003
2,093
1
0
Mb
Nov 28, 2005
#54
  • Nov 28, 2005
  • #54
My 98' ran great after the Pi swap with the plugs gapped at .054. Idled and ran the same as before the swap only the power difference was day-night compared to before.
 
Prev
  • 1
  • 2
  • 3
First Prev 3 of 3
You must log in or register to reply here.

Similar threads

K
Resolved Weird sound coming from a freshly rebuilt 5.0L
  • karhoot
  • Jun 24, 2026
  • Fox 5.0 Mustang Tech
Replies
7
Views
199
Fox 5.0 Mustang Tech Jun 27, 2026
Mac131
A
1987 5.0 speed density Foxbody crank no start
  • Alan2204
  • May 23, 2026
  • Fox 5.0 Mustang Tech
Replies
10
Views
309
Fox 5.0 Mustang Tech May 30, 2026
Mcmahst
G
Fox Tire Size for 16" Pony Wheels on 1984 LX Convertible
  • gw7
  • Jun 24, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
2
Views
117
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Saturday at 7:13 PM
Qtrhrse23
Q
B
Screamin Demons Worth It N/A?
  • Blackout67
  • Oct 20, 2025
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
1
Views
273
1996 - 2004 SN95 Mustang -General/Talk- Oct 20, 2025
Noobz347
M
Misfire
  • Mike3
  • May 30, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
1
Views
94
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- May 30, 2026
Mike3
M
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?