Piston ring end gap excessive on rebuild

91notchbk

Member
Nov 20, 2006
163
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16
Jackson Michigan
home.comcast.net
I am currently rebuilding my 306. I have issues with the valve guides and while the heads off I decided while I had it apart I would put in new bearings and new rings. I ordered rings from Summit and they are made by Hastings. Upon measuring the end gap I have .024 end gap on the top compression ring and .023 on the second compression ring. The spec according to Hasting is max of .022. Ideally I would like to run the gap at .018. It is naturally aspirated and puts out 318rwhp at the wheels. The bore measures 4.0315.

I am wondering if anyone has had this issue?

I am contemplating whether to run these rings, or order .040 rings and file them to fit???
 
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91notchbk

Member
Nov 20, 2006
163
1
16
Jackson Michigan
home.comcast.net
I have not recieved any responses. Apparently, most guys just put in the rings without checking the end gap.

Anyways, I called Hastings and they said that the rings sometimes are manufacturerd on the loose side. According to them this is better than having too little gap. In additon they said I will have no issues running the rings with the current gap even though it is a little above max spec. They also said according to a study it takes .040 above max spec to see any problems with oil consumption on a 4'' bore. So according to the study my max spec is .020, plus .040 is .060. So I would need like .060 to have an issue. So I will be fine at .024 end gap.
 

bhuff30

Founding Member
Dec 11, 2001
6,035
35
129
Olathe KS
I wouldn't worry about the extra ring gap. As you mentioned, the major concern is too little gap allowing the ring ends to touch under heavy load/high heat. You may want to check the piston clearance more carefully... the extra ring gap could be a sign that your bores are slightly bigger than you thought.

Last time I put the 2.3 together, I built it with a minimum gap of around .032 on a 3.810" bore. Even with 22psi of boost, I don't get any noticible blowby or oil burning.

I have not recieved any responses. Apparently, most guys just put in the rings without checking the end gap.

Anyways, I called Hastings and they said that the rings sometimes are manufacturerd on the loose side. According to them this is better than having too little gap. In additon they said I will have no issues running the rings with the current gap even though it is a little above max spec. They also said according to a study it takes .040 above max spec to see any problems with oil consumption on a 4'' bore. So according to the study my max spec is .020, plus .040 is .060. So I would need like .060 to have an issue. So I will be fine at .024 end gap.
 

EMW150

Founding Member
May 22, 2000
2,020
1
46
47
Roaring Spring,PA
This is why I always buy file fit rings. It's more work but worth it in my opinion. On the upside, if you decide to run nitrous down the road you won't have to worry about the ring gap being too tight. It'll be fine for N/A also.
 

2002BLGT

Well-Known Member
Dec 18, 2003
2,945
4
59
Bedford VA
www.dirtydirtyracing.com
Im running 24 and 22 gaps on my nitrous motor that I have yet to spray , 11.5 to 1 compression 306 , has ran a 7.67 in the eigth on motor so far , gonna try to spray it in the 6s if the tranny will hold it for a few passes
 

thumper460

Founding Member
Jul 24, 2000
3,022
0
56
Orange Park , Fl
Thumperoforangepark.com
The second ring gap has been found that it will stop ring "Flutter" if it is wider than the top ring!! Ie: .024 top then a .026 second ring. This has been the norm on performance ring sets for a few years now!! SOOooo... check it out, yes??

Just me...........

Thumper
 

EMW150

Founding Member
May 22, 2000
2,020
1
46
47
Roaring Spring,PA
The second ring gap has been found that it will stop ring "Flutter" if it is wider than the top ring!! Ie: .024 top then a .026 second ring. This has been the norm on performance ring sets for a few years now!! SOOooo... check it out, yes??

Just me...........

Thumper
Same here, I always go wider 2nd gap because just like Thumper said, the gas trapped between the top and 2nd ring can cause the top ring to lift and leak compression. The old school said to go tighter on the top ring because it's exposed to direct combustion.
 
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