Gapping LS piston rings for boost
Thread Starter
Teching In
Joined: Jun 2014
Posts: 3
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From: Salisbury, MD
I have a 5.3L block on the stand with the crank installed. I was thinking I could gap the rings for 8-10 lbs for since I have the opportunity.
I read that some here have used .026 top & .027 2nd, and .025/.025 2nd. Denmah probably wouldn't care.... but like I said I have the engine on the stand and its cheap insurance that doesn't cost much.
This is my first LS build, I've built mostly 2nd Gen SBCs. I want to build to a street friendly NA 5.3 that will be boost-friendly down the road, without changing anything inside.
I read that some here have used .026 top & .027 2nd, and .025/.025 2nd. Denmah probably wouldn't care.... but like I said I have the engine on the stand and its cheap insurance that doesn't cost much.
This is my first LS build, I've built mostly 2nd Gen SBCs. I want to build to a street friendly NA 5.3 that will be boost-friendly down the road, without changing anything inside.
I set them at .030 on top and .028 on the bottom. Seems most do that if they plan for 15 lbs or more boost. 8-10 lbs your are probably ok with stock ring gap, but you know you're going to want to turn it up at some point.
As others have said, leave it at factory. Many, including myself have been more then double what your looking for and for me I had nitrous on top of that. Leave it alone and let it ride.
.026 top .028 2nd. you will not stay at 8-10lbs for long.
it don't take much time or subtract any real performance and it opens up your tuning window for the inevitable mistakes if you're tuning it yourself.
it don't take much time or subtract any real performance and it opens up your tuning window for the inevitable mistakes if you're tuning it yourself.
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Depends on the fuel and tune. I've never butted a ring and run .022 top .024 bottom on quite a few engines. Thats intercooled on E85. Currently running the same gaps on a non-intercooled e85 setup at 9lbs or so.
Usually 100k+ motors are around .022 on the top anyway which is why leaving them alone most of the time is fine. I say always check them. I've seen some as tight as .016 on the top.
I can see going with .024 or so on the top for a pump gas setup for some extra room. More than that seems excessive. I go .002 larger on the 2nd ring.
Usually 100k+ motors are around .022 on the top anyway which is why leaving them alone most of the time is fine. I say always check them. I've seen some as tight as .016 on the top.
I can see going with .024 or so on the top for a pump gas setup for some extra room. More than that seems excessive. I go .002 larger on the 2nd ring.
If the engine is already apart then there's no sense in not gapping the rings.
.025/.027 seems to be the middle ground of what guys are doing.
I've read several guys on here say that the factory gaps can be all over the place so I say check them.
Also to say your gonna stay at 8-10lbs. on a 5.3 isn't gonna happen either.
I'm running 12lbs. on a SBE LS1 with a beat up piston lol.
.025/.027 seems to be the middle ground of what guys are doing.
I've read several guys on here say that the factory gaps can be all over the place so I say check them.
Also to say your gonna stay at 8-10lbs. on a 5.3 isn't gonna happen either.
I'm running 12lbs. on a SBE LS1 with a beat up piston lol.
some motors ive opened up were like .015 on the top ring, and some were .030 or more. they are indeed all over the place. whatever numbers you go with, it won't hurt to take a peek at the turkey.
I get its a JY engine but I'm not in the habit of blowing up engines so I'd check it and have piece of mind.
OEM pistons aren’t going to swell like some of the race alloy forged stuff. A 3.78” bore OEM piston shouldn’t’ need the .025-.030 gaps we hear thrown around in build threads all the time. Esp. on a mild boost build. When’s the last time we’ve heard of a failure due to ring butting in the forced induction section?
I’d bet there’s a good 20-30hp lost by over gapping combined with reusing old rings and not honing the used LS stuff. Bottom line is you give up power with poor ring seal and excessive gap. Sure gambling with excessively tight rings can bite you, and you can make good power either way. But why give up free power? I also had what I consider excessive blow-by with a .028 gap. I've heard of others that did not have this problem, but I sure did.
If you have something torn down completely, I’d hone it with new rings. .050-.055 x bore is plenty on OEM pistons IMO.
Stock48’s stuff is a good example. Pretty sure I recall his SBE 6.0 stuff was gapped at .018, and that’s on the 4” bore. He also used new GM rings and made sure of a good bore/hone.
Some more big power guys with .017 top gaps here on the bigger bore motors.
https://ls1tech.com/forums/forced-in...l#post19628281
I’d bet there’s a good 20-30hp lost by over gapping combined with reusing old rings and not honing the used LS stuff. Bottom line is you give up power with poor ring seal and excessive gap. Sure gambling with excessively tight rings can bite you, and you can make good power either way. But why give up free power? I also had what I consider excessive blow-by with a .028 gap. I've heard of others that did not have this problem, but I sure did.
If you have something torn down completely, I’d hone it with new rings. .050-.055 x bore is plenty on OEM pistons IMO.
Stock48’s stuff is a good example. Pretty sure I recall his SBE 6.0 stuff was gapped at .018, and that’s on the 4” bore. He also used new GM rings and made sure of a good bore/hone.
Some more big power guys with .017 top gaps here on the bigger bore motors.
https://ls1tech.com/forums/forced-in...l#post19628281
Last edited by Forcefed86; Jul 21, 2017 at 12:22 PM.
OEM pistons aren’t going to swell like some of the race alloy forged stuff. A 3.78” bore OEM piston shouldn’t’ need the .025-.030 gaps we hear thrown around in build threads all the time. Esp. on a mild boost build. When’s the last time we’ve heard of a failure due to ring butting in the forced induction section?
I’d bet there’s a good 20-30hp lost by over gapping combined with reusing old rings and not honing the used LS stuff. Bottom line is you give up power with poor ring seal and excessive gap. Sure gambling with excessively tight rings can bite you, and you can make good power either way. But why give up free power? I also had what I consider excessive blow-by with a .028 gap. I've heard of others that did not have this problem, but I sure did.
If you have something torn down completely, I’d hone it with new rings. .050-.055 x bore is plenty on OEM pistons IMO.
Stock48’s stuff is a good example. Pretty sure I recall his SBE 6.0 stuff was gapped at .018, and that’s on the 4” bore. He also used new GM rings and made sure of a good bore/hone.
Some more big power guys with .017 top gaps here on the bigger bore motors.
https://ls1tech.com/forums/forced-in...l#post19628281
I’d bet there’s a good 20-30hp lost by over gapping combined with reusing old rings and not honing the used LS stuff. Bottom line is you give up power with poor ring seal and excessive gap. Sure gambling with excessively tight rings can bite you, and you can make good power either way. But why give up free power? I also had what I consider excessive blow-by with a .028 gap. I've heard of others that did not have this problem, but I sure did.
If you have something torn down completely, I’d hone it with new rings. .050-.055 x bore is plenty on OEM pistons IMO.
Stock48’s stuff is a good example. Pretty sure I recall his SBE 6.0 stuff was gapped at .018, and that’s on the 4” bore. He also used new GM rings and made sure of a good bore/hone.
Some more big power guys with .017 top gaps here on the bigger bore motors.
https://ls1tech.com/forums/forced-in...l#post19628281
I've got a Gen IV 5.3 that I picked up some 4.8 flat top pistons for and I'm on the fence as to reuse the stock rings or bottle hone the bores and buy new rings.
I really don't want to sink a bunch of money into a short block I'm only into for $200 lol.
man i just cant keep up with the trends on here anymore.
run tr6's NO DONT RUN TR6's
gap your rings wide open with stock pistons, no run small OEM gaps
run tall rearend gears, no run some short gears dont be a dummy!
im just gonna stick to what im doing lol
run tr6's NO DONT RUN TR6's
gap your rings wide open with stock pistons, no run small OEM gaps
run tall rearend gears, no run some short gears dont be a dummy!
im just gonna stick to what im doing lol
Its a Gen IV with 130K on it, good rods and pistons.
That's what I'm thinking though, reuse as much as I can and see what it makes.
With CNC ported 317 heads, LJMS Stage 2 cam and a T7875 feeding it 18 lbs. of boost I'm shooting for 750ish rwhp on 92 pump swill with a little meth if needed.
What grit flex hone do you recommend?
No ***** given JY build don't gap it and if it blows throw another short block in it.
OR
Yeah its a JY build but I still don't wanna blow it up so I'll do the little stuff that doesn't incur additional costs.
At least that's how I see it, I'm the latter btw lol.
Originally Posted by truckdoug
man i just cant keep up with the trends on here anymore.
run tr6's NO DONT RUN TR6's
gap your rings wide open with stock pistons, no run small OEM gaps
run tall rearend gears, no run some short gears dont be a dummy!
im just gonna stick to what im doing lol
run tr6's NO DONT RUN TR6's
gap your rings wide open with stock pistons, no run small OEM gaps
run tall rearend gears, no run some short gears dont be a dummy!
im just gonna stick to what im doing lol