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Piston Ring Gap [Merged 5-7] gapping rings pistons end filing

wortdog

Proven Member
172
4
Jun 23, 2003
Champaign, Illinois
I set mine to around .0195 on top and .0230 bottom, but the motor is still sitting on the stand awaiting time to put it in.
 

SnowBird

Proven Member
528
0
Jul 9, 2006
Cleveland, Ohio/Tampa, Florida
I checked all the other rings and the #1 ended up being .020 so they are significantly smaller than the .029 of the bottom one, if anything this will just be safer? I read somewhere that its sometimes better to open up the bottom ring a little more. If this isnt true I just sound stupid.

And I ended up just pulling the rings out with my hands, no where near as smooth as the pistons pushed them down, but nothing to worry me.
 

2alpha

Proven Member
51
0
Aug 15, 2006
Fairbanks, Alaska
I seem to be having a lot of excessive blow-by. I just rebuilt my motor. Right now i have my piston rings gapped at .018 inches top, .014 inches 2nd, and .018 inches oil ring and I haven't done a compression test yet because if the gap aren't correct, theres no reason because i'll have to rip it apart again. What you guys think?

[Nice search job.]
 

TwoLiterLaser

Proven Member
588
11
Jul 20, 2005
Cincinnati, Ohio
How many miles do you have on the engine since the re-build? The two engines I have rebuilt took a little bit of mileage to break in completely. I had blow-by like you are saying also.

As far as the ring gaps, I do not have access to my manual right now, but I do know that the gap size can depend on your pistons and what rings you use. So, did you follow a manufacturers recommendations? Or use stock ring gap?
 

AK_4g63t

Proven Member
100
1
Apr 21, 2007
Fairbanks, Alaska
Alright, I did some research for you. After reading and reading I found out that if you plan on running your big evoIII at about 20psi I would have put the top at around .018inches, the middle at around .022 inches and to not gap the oil ring. Also, yes.. how many miles are on that motor cause it has taken some people 500+ miles to seal those rings.
-Donny
 

2alpha

Proven Member
51
0
Aug 15, 2006
Fairbanks, Alaska
I have roughly 1000 miles on the engine. I was working on it today and i experimented with the PCV and noticed that my hose was slightly kinked. So I cut it and eliminated the curve with a piece of piping at a 90 degree angle. Also i noticed that my oil was as dirty as it is when it needs to be changed after 3000 miles. It only has 500 on it and its already been changed twice. And i know i have a leak in the turbo area...so let me run this by.
If i had a leak big enough in my turbo to make me a quart low on oil every 4-7 days, could it be possible that oil lubricating the turbo is being pressurized back to the crank case by the turbo itself, causing the added pressure there?
 

AK_4g63t

Proven Member
100
1
Apr 21, 2007
Fairbanks, Alaska
I say a bad piston ring seal with the cylinder and you are getting exhaust in your crankcase and causing it to get dirty, all while cause excessive blow-by. Am I correct anyone? If you want to do a compression test I've got the goods but I'm sure your dad has the tools. Come by my work one day, I want to check out "the beast"
-Donny
 

2alpha

Proven Member
51
0
Aug 15, 2006
Fairbanks, Alaska
Its possible for sure. He actually told me to take a pressure gauge and hook it up to the blow-by and see how much pressure there is and go from there. He suggested removing one spark plug from each cylinder at a time and then running the car to see if the pressure goes down. If it never changes, then you know its not a ring. Does that sound right to anyone?
 

Maglin

Proven Member
872
13
Apr 30, 2004
Wichita, Kansas
That will give you what cylinder is causing the excessive blow by.

Alpha your second ring of .014" is way to small. You top ring is correct as per Weisco but you 2nd ring should be .020" gap. With the second ring gap less than the top you are going to experience top ring flutter and actually end up wearing out the ring land and it probably won't seal as well either. Also if you install the oil ring expander incorrectly you can get excessive oil consumption. The oil control rings don't need gapped. Here is a link to help everyone with ring end gap.

Ring Gap PDF
 

want_a_gsx

Proven Member
257
2
Apr 3, 2006
Milwaukee, Wisconsin
Ok so I just got done researching ring gap suggestions (including the 8 page thread) and figured out the suggested ring gap is:

top ring- .017-.019"
#2 ring- .021-.023"

I contacted the rebuilder who is in charge of rebuilding the motor and he told me that he gapped the top rings at .015-.016" from what he remembers, but still has to double check where he wrote it down. The bottom end is completely assembled. I was wondering if this ring gap would be fine to run around 20 psi on a hx35, or 360ish whp. I tried conveying him that the gap needs to look like ^^^ but he insists that stock ring gap will do just fine.

My current mods are not up to date, since none of them are on the car yet (motor isn't in car obviously). Mod list will look like this:

-255 lph
-850cc inj
-Keydiver & SAFC
-hx-35 w/ BE housing
-sbr exh mani
-Lan fmic
-act 2600
-ferrea valves, guides
etc...

What do you guys think? Does the gap need to be increased to the recommended size by the fellow tuners?
 

RichCaccese

Proven Member
98
1
Jul 7, 2003
Staten Island, New_York
Here is a good read:

Author Larry Carley

.....some engine builders who have switched the rings they use to a set that includes a "gapless" top compression ring say they've gained three to five percent more horsepower with no other changes. Gapless rings are available in popular sizes with various wear-resistant face and side coatings. On some engines, the second compression ring can be eliminated if a gapless top ring is used. Getting rid of the second compression ring cuts friction and adds horsepower, too.
SMOOTHER, FLATTER....

If you actually read this then you would see that the opinion of the author is to have a larger 2nd ring gap on an engine like the modified 4G63. I would agree.

Jake H

I'm glad i found this informative thread.

I purchased a set of Total Seal (gapless top) rings. I also have the Wiesco rings that came with the pistons. I am considering installing the Total Seal set, but the whole 2nd ring elimination idea makes me worry. Anyone have ideas about this "trend"? Any suggestions, ideas or thoughts will be appreciated.

btw, putting together a wiesco/eagle 2.0 @ 9:1, looking to run an FP3565, goal= 500whp.
 

phillabaum03

Proven Member
851
3
Nov 28, 2005
sharpsville, Pennsylvania
How far off would the gap have to be to cause massive blow by.. Like plugs covered in oil. Oil coming out of exhaust leaks..
 

tsunari

Proven Member
1,029
32
Feb 12, 2003
Jessup, Maryland
How far off would the gap have to be to cause massive blow by.. Like plugs covered in oil. Oil coming out of exhaust leaks..

You sure it's blow-by? With that much oil, perhaps you have bad valve stem seals?
 

Enraged78

Proven Member
728
13
Jul 17, 2002
South Windsor, Connecticut
How far off would the gap have to be to cause massive blow by.. Like plugs covered in oil. Oil coming out of exhaust leaks..

Do a compression and leakdown test. I had something similar with large amounts of oil consumption, in the neighborhood of 1 quart every 400 miles. Now, I gapped my rings fairly loose (according to the Ross formula, I gapped for 600HP and added a thousandth) I did a compression and leakdown test, and the results were great. 176 across all four, and 2% leakdown. This led me to believe the problem wasn't rings. I pulled the head (which an unnamed shop had "rebuilt" for me) and had it checked by an independant shop. Turns out that there was substantial egg-shaping of the valve stems, and the valve guides were out by over three thousandths. Basically, all the shop did was to clean the head, deck it, and stick new seals in. They never checked the valves or guides. The head easily had 150,000 hard miles on it.

Long story short, do a compression and leakdown test. If it's good, there's a strong indication that you should look elsewhere, such as the turbo or the head. Also make sure that you have plenty of room to vent your valve cover. Excess crankcase pressure from loose rings can cause all kinds of issues. Oil can back up the turbo drain tube and force itself into the compressor, fouling your intake track and making its way into your combustion chamber.

Hope this helps,
Matt.
 

SlickPyro

Proven Member
226
6
Jun 5, 2008
South Euclid, Ohio
I am bringing this thread back from the dead cause I have a huge problem. I stock rebuilt my six bolt and bought topline .020 over pistons and ring set. The bore is .020 over just to clear up any confusion. I put the rings on and put the pistons in and put the engine in. The engine is ready to fire. Just a few more things like boost gauge and wideband to hook up. My friend asked me today what I set my ring gap to. I said whatever they came as. I didnt know you had to do that. So my question to everyone is will it be ok or should I not even bother firing it and the pistons should be pulled back out and the rings gapped? Thanks.
 

alexg1323

Proven Member
263
7
May 11, 2004
na, Michigan
topline comes pre-gapped it will be with stock specs. Its a low performance OEM replacement. Though its definatly good practice to check your specs before final assy. you will be fine im sure. High performance rings come gapped below specs so the builder can gap them to there specific performance needs. Manufactures like wiseco, JE, etc.
 

SlickPyro

Proven Member
226
6
Jun 5, 2008
South Euclid, Ohio
Well thats good to hear. I am going to do a bit more research to make sure that they are going to be ok so I don't crack one. I don't plan on throwing much at these pistons. I did a stock rebuild, 14b and in the long run I'm only gonna run 15lbs. I'm going to start at wastegate pressure for a few weeks and then 10lbs and then 15. Thanks for the help alex.
 

DSM_PWR

Proven Member
2,459
18
Oct 12, 2007
Austin, Texas
Actually, since you got the block bored .020 over its a REALLY good idea you double check...

Different machine shops will bore at different thousands of a tenths and its always best to check the ring gap to make sure everything is within spec
 

alexg1323

Proven Member
263
7
May 11, 2004
na, Michigan
as long as your block was bored within stock specs which should have been measured infront of you at the machine shop with a depth mic if you didnt have the tools yourself then i guarenttee you the rings will be fine. I have used topline rings in builds in the past and they are always dead on to stock specs around .16 ring 1 i believe its been awhile since ive built. Reguardless topline also swears by them being pre gapped. call them up and speak with tec support over it. I would certainly not tear the engine back apart to check from parinioa the retorquing of the head gasket alone would outweigh that decision for me. I think your fine and you will be able to abuse that engine as much as a stock engine with those rings all other things considered
 

alexg1323

Proven Member
263
7
May 11, 2004
na, Michigan
read my post from 2 years back #167 where i talk about topline ring gap in a 020 bored over situation. I am actually complaining there pre gapped rings they sent me were on the lose side of the specifications. This is with a 020 bore balanced perfectly in its tolerances.
 

1990gsx1781

Proven Member
190
1
Jun 28, 2008
Lynn, Massachusetts
ok so i got a really nice new set up but not gonna lie when it comes to piston rings i suck so i had the machine shop do them when i got them back the gaps seemed a little big... its a .020 bore block with stock crank manely rods, wiseco coated pistons and the top gap is .021 and the second ring gap is either .020 or .021 also does this seem right thank you guys
 

crimsondragon

Proven Member
4,301
50
Dec 17, 2006
Phillipsburg, New_Jersey
I know. That's what I heard as a selling point for Wiseco. But since you sent it off to the machine shop they might have ####ed with them. Do you know if they changed the gap?
 
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