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

What is the ring-gap size for std 302?

  • Thread starter Thread starter 5ptslow
  • Start date Start date Apr 14, 2005
5

5ptslow

Founding Member
Oct 24, 2002
105
8
18
Westland, MI
Apr 14, 2005
#1
  • Apr 14, 2005
  • #1
what size is it? and do you also file down the oil rings?
have not put a motor together in a long time. thanks for the help
 

Jason 302

10 Year Member
Aug 9, 2003
685
71
68
Newark, Ohio
Apr 14, 2005
#2
  • Apr 14, 2005
  • #2
5ptslow said:
what size is it? and do you also file down the oil rings?
have not put a motor together in a long time. thanks for the help
Click to expand...

The oil rings are usually pre-fit, as long as you order them for your bore size. Gap the compression rings at 0.016-0.018 for a 4.00 bore, 0.018-0.020 for a 4.030 bore. Go about 2-4 thousandths bigger if you plan on running boost or nitrous.

The rings you get should come with directions on what to gap. My Speed Pro rings actually called for a larger gap on the second rings, which is opposite of what the rule has always been. They say a larger second gap lessens pressure build up between the two, making it less likely to lift the first ring off it's land. I just gapped both at 0.020".
 
P

peabody

New Member
Apr 6, 2005
1
0
0
Apr 14, 2005
#3
  • Apr 14, 2005
  • #3
What would happen if you just installed you rings without checking them?
 

Jason 302

10 Year Member
Aug 9, 2003
685
71
68
Newark, Ohio
Apr 14, 2005
#4
  • Apr 14, 2005
  • #4
The reason for gapping your rings is because the heat makes them expand. You have to have clearance between the ring ends to make room for this expansion. If the gap is too wide, it will hurt your compression and may make oil consumption an issue. If the gap is too small, the ring ends will butt into each other and gouge your cylinder wall, which, of course, isn't good. It could also make your ring break because of the pressure.
 
5

5ptslow

Founding Member
Oct 24, 2002
105
8
18
Westland, MI
Apr 14, 2005
#5
  • Apr 14, 2005
  • #5
well i put the rings about 1 1/2 inches into the bore and put a feeler gauge in the gap and i got .029 is this correct? or do i need to file em? oil ring seems way over sized.
 

Jason 302

10 Year Member
Aug 9, 2003
685
71
68
Newark, Ohio
Apr 14, 2005
#6
  • Apr 14, 2005
  • #6
5ptslow said:
well i put the rings about 1 1/2 inches into the bore and put a feeler gauge in the gap and i got .029 is this correct? or do i need to file em? oil ring seems way over sized.
Click to expand...

Did you use a piston to push it down in? This will make sure the ring is square in the bore for an accurate measurment.

Oil rings don't have to be as precise as the compression rings. I think Haynes calls for no more than 0.055 for the oil rings. Or are you saying the rings need to be filed. If so, just file them.
 
5

5ptslow

Founding Member
Oct 24, 2002
105
8
18
Westland, MI
Apr 15, 2005
#7
  • Apr 15, 2005
  • #7
well i did put them in square with a square and the reading i got was .029. so i guess im breaking out the file.
so i need it to be .050 to .055
 

Jason 302

10 Year Member
Aug 9, 2003
685
71
68
Newark, Ohio
Apr 15, 2005
#8
  • Apr 15, 2005
  • #8
5ptslow said:
well i did put them in square with a square and the reading i got was .029. so i guess im breaking out the file.
so i need it to be .050 to .055
Click to expand...

Your talking about the gap on your oil rings, right? No no, 0.055 is the max allowed. 0.029 is perfectly fine for oil rings.

Instructions with my Speed Pro rings.

TOP RINGS
0.004 for every inch of bore size (ie: 4.000 bore= 0.016")

SECOND RINGS
0.005 for every inch of bore size (ie: 4.000 bore= 0.020")

OIL RINGS
snug fit.

The oil rings don't take as much heat as the top two, so gap isn't as critical. I would say you would want it anywhere from 0.015-0.035.
 
5

5ptslow

Founding Member
Oct 24, 2002
105
8
18
Westland, MI
Apr 15, 2005
#9
  • Apr 15, 2005
  • #9
no thats the size that the top 2 rings .029
 

Jason 302

10 Year Member
Aug 9, 2003
685
71
68
Newark, Ohio
Apr 15, 2005
#10
  • Apr 15, 2005
  • #10
5ptslow said:
no thats the size that the top 2 rings .029
Click to expand...

You never did tell me what your bore size is. Either way, that's a lil wide, don't file them any more. If you plan on boost or nitrous in the future, your all set. (assuming the rest of your parts can handle it. lol)
 
You must log in or register to reply here.

Similar threads

Fox won't crank over and fuel pump won't kick on.
  • djj62478
  • Jun 7, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
16
Views
364
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 11, 2026
General karthief
H
Brand New Built 302 overheating
  • hassler
  • Sep 26, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
23
Views
1K
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Oct 26, 2025
Rcdgl
R
D
Engine HO cam in non HO roller block ‘93 f150
  • DanC1993f150
  • Mar 21, 2026
  • Fox 5.0 Mustang Tech
Replies
7
Views
344
Fox 5.0 Mustang Tech Mar 29, 2026
General karthief
X
Free VE Table Corrections — Drop Your MSQ and a Datalog, I'll Do the Rest
  • X-cam34
  • Apr 12, 2026
  • Digital Self-tuning Forum
  • 2 3
Replies
44
Views
1K
Digital Self-tuning Forum Monday at 1:31 AM
X-cam34
X
F
Fox 1990 Mustang GT 5.0 A9L – Engine suddenly shuts off but immediately restarts when key turned
  • FishermansFriend
  • Sunday at 9:39 AM
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
2
Views
48
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Sunday at 3:32 PM
AeroCoupe
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?