• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

Thermo Plugs Arent Working

  • Thread starter Thread starter 1/4 Mile Style
  • Start date Start date Dec 7, 2009

1/4 Mile Style

New Member
Mar 13, 2004
36
0
0
Dec 7, 2009
#1
  • Dec 7, 2009
  • #1
So I got these plugs in for my heads that Sleeper suggested and they dont fit. Seem too big??

Any other ideas for plugging the emission holes on the back of the head or is there some trick to getting these in....

...this is the only thing holding me up from getting the car running now.


TIA, Jon
 

Vinnietbird

Member
Jun 2, 2005
584
3
19
Dec 7, 2009
#2
  • Dec 7, 2009
  • #2
I cut the ends off of the thermactor pipe,and tuned them backwards,used a little Permatwx,and bolted them on.No leaks for three years so far.Took about 5 minutes total.
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,177
17,879
224
Massachusetts
Dec 7, 2009
#3
  • Dec 7, 2009
  • #3
I beleive they are the same threads as spark plugs. I think i've heard of guys using two old plugs and breaking the porcelean head off.
 

liljoe07

5 Year Member
Feb 18, 2009
1,622
363
124
Cartersville,Ga
Dec 7, 2009
#4
  • Dec 7, 2009
  • #4
Should be 5/8-11 thread. You can get them at Home depot or lowes with and allen head. Just like a set screw. Make sure your not using the crossover tube mounting hole instead of the actual thermactor port.
 

4G-KDMP

10 Year Member
Jul 23, 2005
935
19
39
CA
Dec 7, 2009
#5
  • Dec 7, 2009
  • #5
The bolt is 5/8-11 thread the same as a spark plug. Sounds like there could be a lot of carbon build up on the threads, did you try cleaning the threads in the back of the heads?
 

1/4 Mile Style

New Member
Mar 13, 2004
36
0
0
Dec 7, 2009
#6
  • Dec 7, 2009
  • #6
Whats the diff between the thermo port and the crossover tube port? Theres only one hole on each head in the bottom outside corner on mine. The plugs I bought are the TF 5/8-11's but they definately dont thread in.

Just tried an old spark plug and that seems spot on but they are a little smaller than the therm plugs & are a fine thread v.s course.

I dont guess it matters if it crossthreads as these will never be coming out of my motor????
 

1/4 Mile Style

New Member
Mar 13, 2004
36
0
0
Dec 7, 2009
#7
  • Dec 7, 2009
  • #7
This pics shows that the therm plugs that I got are indeed a little bigger than the spark plugs....
 

1/4 Mile Style

New Member
Mar 13, 2004
36
0
0
Dec 7, 2009
#8
  • Dec 7, 2009
  • #8
Think I got it figured out. Used the broke off sprak plugs. These pupies are SNUG. I dont see any way theyre coming out.
 
You must log in or register to reply here.

Similar threads

Engine Suggestions on an engine rebuild. Stock cam/GT40Ps or aftermarket on both for a fun weekend driver?
  • MadSquirrelTech
  • Apr 28, 2026
  • Fox 5.0 Mustang Tech
  • 2
Replies
23
Views
606
Fox 5.0 Mustang Tech May 7, 2026
MadSquirrelTech
S
Fox '87 GT can't get to stay running
  • spilly
  • Mar 29, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
26
Views
574
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Apr 25, 2026
CAMTWO1070
M
Engine 1988 Foxbody - Overheating Summer
  • MDrisc
  • Oct 26, 2025
  • Fox 5.0 Mustang Tech
Replies
10
Views
492
Fox 5.0 Mustang Tech Nov 28, 2025
Mustang5L5
D
Engine Coolant and Radio Issues
  • Don7Up
  • Sep 14, 2025
  • Fox 5.0 Mustang Tech
Replies
17
Views
569
Fox 5.0 Mustang Tech Oct 4, 2025
Don7Up
D
Y
2004 Roush - Dome Lights and radio not working
  • Yurei
  • Nov 10, 2025
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
8
Views
360
1996 - 2004 SN95 Mustang -General/Talk- Nov 20, 2025
squeak93
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 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?