Urgent Piston Ring Gap - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums
 
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post #1 of 11 (permalink) Old 02-10-2010, 10:32 PM Thread Starter
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Piston Ring Gap

I am starting the reassembly of my engine. Its an LT1 bored .030 over with forged pistons, rods, and crank. Anyways its also gonna eventually see some nitrous.....an occasional 100-150 shot. So my question is what should I gap my piston rings at? What is the stock gap at......and if its just a little nitrous every now and then, should I worry about going with a wider gap?


Also can someone throw out a link with all the torque specs on all the bolts/fasteners for a rebuild.......I know, I'm lazy.

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Last edited by Formula4Fast; 02-10-2010 at 10:35 PM.
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post #2 of 11 (permalink) Old 02-11-2010, 09:12 AM Thread Starter
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Anybody? Kinda waiting on an answer before I move forward in my build...

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Forged 355ci LT1, Ported Heads w/ Bullet 2700R valve springs, CC503 cam, Moroso CAI, TrickFlow Elbow, TB Foil, Ported MAF, MSD Coil, MSD Opti, MSD Wires, LT Race Headers, 3" true dual exhaust/x-pipe/magnaflow mufflers, !EGR/!Air, LT4 KM, Transgo shift kit, Tuned By Trifecta.
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post #3 of 11 (permalink) Old 02-11-2010, 09:49 AM
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You should contact your ring company to find out about the gap when using nitrous.

According to the GM 96 FSM, here are the stock ring gaps:

TOP COMPRESSION PRODUCTION: .010-.016 IN
2ND COMPRESSION PRODUCTION: .018-.026 IN
OIL RING GAP PRODUCTION: .010-.030 IN

Jake

My son, Ryan M. Cameron, graduated from West Point on 22 May 2010! He was commissioned as a 2nd Lieutenant and I pinned on his first pair of "Butter Bars" PROUDEST DAY OF MY LIFE!!

1996 Vette, 388 CID LT1 (3.75" X 4.060"), Eagle Internally Balanced Forged Crank, Eagle 6" Forged Rods, SRP Forged Pistons, CompCams XFI 467 Cam (230/236 @ .050), Scorpion 1.7 RRs, AFRs ported to 212 ccs (304 cfm @.600), Match Ported LT1 Intake, SVO 30# Injectors, BBK 58mm
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post #4 of 11 (permalink) Old 02-11-2010, 10:50 AM Thread Starter
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Thanks for the info, but would stock ring gaps apply to an engine thats bored .030 over?

Mods List....
Forged 355ci LT1, Ported Heads w/ Bullet 2700R valve springs, CC503 cam, Moroso CAI, TrickFlow Elbow, TB Foil, Ported MAF, MSD Coil, MSD Opti, MSD Wires, LT Race Headers, 3" true dual exhaust/x-pipe/magnaflow mufflers, !EGR/!Air, LT4 KM, Transgo shift kit, Tuned By Trifecta.
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post #5 of 11 (permalink) Old 02-11-2010, 11:39 AM
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Quote:
Originally Posted by Formula4Fast View Post
Thanks for the info, but would stock ring gaps apply to an engine thats bored .030 over?
Yes. Use of nitrous can call for more though.

Jake

My son, Ryan M. Cameron, graduated from West Point on 22 May 2010! He was commissioned as a 2nd Lieutenant and I pinned on his first pair of "Butter Bars" PROUDEST DAY OF MY LIFE!!

1996 Vette, 388 CID LT1 (3.75" X 4.060"), Eagle Internally Balanced Forged Crank, Eagle 6" Forged Rods, SRP Forged Pistons, CompCams XFI 467 Cam (230/236 @ .050), Scorpion 1.7 RRs, AFRs ported to 212 ccs (304 cfm @.600), Match Ported LT1 Intake, SVO 30# Injectors, BBK 58mm
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post #6 of 11 (permalink) Old 02-11-2010, 12:35 PM Thread Starter
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K, thanks for the info. It is greatly appreciated!

Mods List....
Forged 355ci LT1, Ported Heads w/ Bullet 2700R valve springs, CC503 cam, Moroso CAI, TrickFlow Elbow, TB Foil, Ported MAF, MSD Coil, MSD Opti, MSD Wires, LT Race Headers, 3" true dual exhaust/x-pipe/magnaflow mufflers, !EGR/!Air, LT4 KM, Transgo shift kit, Tuned By Trifecta.
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post #7 of 11 (permalink) Old 02-11-2010, 03:23 PM
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Quote:
Originally Posted by JAKEJR View Post
You should contact your ring company to find out about the gap when using nitrous.

According to the GM 96 FSM, here are the stock ring gaps:

TOP COMPRESSION PRODUCTION: .010-.016 IN
2ND COMPRESSION PRODUCTION: .018-.026 IN
OIL RING GAP PRODUCTION: .010-.030 IN

Jake
I'm not sure what piston/ ring setup your using but the rings I have for my forged pistons call for a lot less gap then what factory is I can't remember what the specs were but I do remember that with a 200+shot they only needed .009-.010 for the top and thats on the low side for stock so I highly suggest you contact the ring manufacturer

94 Z28: 383 12.5:1 forged 4340 crank, forged H beam rods, forged -5cc Mahle pistons, H series bearings all around, B&M flex plate, keyed hub, LE2 heads, custom LE grind, LE ported intake, BBK 58mm, LS7 lifters, comp hi-tech push rods, 1.6 nsa Pro mags, patriot golds, 42lb green tops, ARP bolts all around, canton 6qt pan, pacesetter coated long tubes backed by a magnaflow

93Z basically a car in a box...well three boxes ... one box down
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post #8 of 11 (permalink) Old 02-11-2010, 09:41 PM
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depends onwhat rings you are going to use, and a .030 over bore will call for a hair more gap. the gap is figured depending on the material and the total bore, bigger hole, bigger piston, bigger ring = more gap. smaller bore, smaller hole, smaller piston, smaller ring = less gap. the more ring face or bigger ring has more material and has to have more room to grow

nitrous is like a slut you want hit it but your afraid of the aftermath, 94 z28,m6,1.6 rr,riased guide plates,moroso cai,airfoil,jet babyback,7.2 hardend pushrods,pacesetter coated lt and ory,eld. sdt cat back,2000 camaro rear with 4.10,17x10 and 17x11 1/2 torqe thrust, slotted and crossdrilled on all corners, brigth red with hard top. bmr extreme tourqe arm, bmr cromoly lca's and panhard, iceman with shark nozzle, and msd programable dig 7 waiting to be installed.
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post #9 of 11 (permalink) Old 02-12-2010, 12:29 PM
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Here's an interesting experiment I did with ring gaps.

Many years ago i decided to try tighter end gaps to see what gives. my thinking was that tighter gaps would improve ring sealing, lessen blow-by and make the car quicker and faster. So I freshened a 8 second BB engine and set the top and second end gaps at .010"/.010".

MPH fell off a little so I tore down the engine to have a look-see. Using my magnifying glass I could see indications that the ends were butting, so I knew that "plan" didn't work.

There's a rule of thumb on gaps, .004" per inch of bore for the top ring and .005" for the second ring. The second ring gap "constant" was changed some years ago after testing showed that setting the second ring gap wider than the top ring gap improved ring sealing. Before that change, the second ring gap was always set tighter than the top gap.

For engines running nitrous or chargers, it's recommended the gaps be wider - .005"/.006" per inch of bore. This is because the higher heat created by the power adders results in greater ring expansion calling for more gap to prevent butting.

Here are some more gaps; this time taken from the 1986 (eighty-six) GM Vette FSM:

Top Compression Production: .010"-.020"
Second Production: .010"-.025"
Oil Production: .015"-.055"


Hope this helps.

Jake

My son, Ryan M. Cameron, graduated from West Point on 22 May 2010! He was commissioned as a 2nd Lieutenant and I pinned on his first pair of "Butter Bars" PROUDEST DAY OF MY LIFE!!

1996 Vette, 388 CID LT1 (3.75" X 4.060"), Eagle Internally Balanced Forged Crank, Eagle 6" Forged Rods, SRP Forged Pistons, CompCams XFI 467 Cam (230/236 @ .050), Scorpion 1.7 RRs, AFRs ported to 212 ccs (304 cfm @.600), Match Ported LT1 Intake, SVO 30# Injectors, BBK 58mm
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post #10 of 11 (permalink) Old 07-05-2019, 02:23 PM
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Sorry to bump an old thread, but I have a question pertaining to this issue.

97 LT1 with 104k being rebuilt. I honed the cylinders with a borrowed tool from O'reilly.

So I bought engine-tech rings from Rock-Auto and I'm putting them in the cylinders and checking the gaps. Top and second ring are both .025. Second ring, that is barely within specs on the high end. Top ring is bigger than it calls for. If it were tight, I could open it up. But nothing I can do to tighten it in.

Haynes manual says the gap being big isn't a huge deal as long as it's not over .040, which I am well under. Should I just go head, assemble it, and send it? Or should I buy larger rings? I'm guessing it's the 104k miles wear and hone that have slightly enlarged the bore, but I don't get why the ring gaps are the same on both rings. Especially considering the bottom ring is shorter when the two are lined up in hand. Once in, it SHOULD be a larger gap. Not the same.

Any advice before I proceed?

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post #11 of 11 (permalink) Old 07-06-2019, 05:24 AM
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Honing the cylinders, unless you went crazy on them, should not increase the size of the cylinder that much. My thought is defective ring set. Quality control is not what it used to be.

I suggest getting a dial bore gauge and measure cylinder bores. Be sure to get one that reads 0.0001 inch. That's ten thousandths of an inch reading capability. See how much you took off the cylinders. Compare to bore size in 96 factory service manual

Did you cut the ridge off the top of the cylinder, before honing them? Ridge reamer is tool used. Having the ridge still on top of cylinder will break the top rings in short order. So with bore gauge, measure top, middle & bottom of cylinder. By bottom of cylinder, I mean the lowest level that rings touch at bottom dead center.

Actual bottom of cylinder will be unworn as rings don't touch there. Read post #9 for rule of thumb on ring gap.

Last edited by cocobolo95; 07-06-2019 at 05:32 AM.
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