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#2291588 - 04/21/17 12:47 PM Thin vs. Thick Piston Rings
PurpleBeeper Offline
mopar

Registered: 07/05/11
Posts: 505
Loc: Chicago
I'm starting to look for forged pistons for a new motor with nitrous. Most of the forged pistons I see use 1/16", 1/16" 3/16" piston rings. I believe the stock pistons (& some forged) use 5/64", 5/64", 3/16" rings.

On a mainly street nitrous motor, what top/middle ring thickness is better? Why?

What other general knowledge about rings can you guys give me?
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70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"

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#2291603 - 04/21/17 01:11 PM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
Cab_Burge Offline
Too Many Posts

Registered: 08/23/03
Posts: 29720
Loc: Bend,OR USA
The thinner the ring pack the less drag on the cylinder walls, less friction = more power shruggy
On your deal you need to make sure the pistons you buy are for street NOS, not stock or SS racing where the ring lands are raised way up to increase the compression ratio twocents
Are you planning on running a vacume pump? If so then look at the really thin racing rings like 1Mm or the .043 rings with minimal tension twocents Those size rings make a huge difference on the ring drag up
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#2291624 - 04/21/17 01:37 PM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
madscientist Offline


Registered: 09/17/14
Posts: 1689
Loc: Washington
There is never a reason for 5/64 rings on anything automotive anymore.

It was overkill in 1970.


A 1/16 ring pack is as thick as I'd use in a street engine today.
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#2291743 - 04/21/17 05:26 PM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
PurpleBeeper Offline
mopar

Registered: 07/05/11
Posts: 505
Loc: Chicago
I don't plan to run an evac system since this is a 99% street motor. It definitely makes sense that thinner rings = less friction. I've got 1/16", 1/16", 3/16" rings in the current engine with "low tension" oil rings. I swear my rings took 5000 miles to seat! One of the rings is chrome molly, if that matters.
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70 Roadrunner convt. street car 440+6, NOS, 4-spd, SS springs '96 Mustang GT convt. street car '04 4.6 SOHC, NOS, auto, lowered "Officer, that button is for short on-ramps"

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#2291927 - 04/21/17 11:55 PM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
Cab_Burge Offline
Too Many Posts

Registered: 08/23/03
Posts: 29720
Loc: Bend,OR USA
I found out the hard way a long time ago to not use low tension oil rings on any motor that didn't have a vacume pump or dry sump oil system on the motor, especially STREET motors tsk
Stick with the 1/16,1/16 and 3/16 standard tension oil rings and set the end gaps on the wide side, not on the tight side tsk twocents
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Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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#2291936 - 04/22/17 12:15 AM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
FastmOp Offline
master

Registered: 01/20/03
Posts: 4918
Loc: Hot Rod Ridge
Call totalseal

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#2291969 - 04/22/17 02:21 AM Re: Thin vs. Thick Piston Rings [Re: FastmOp]
Jeremiah Offline
master

Registered: 03/03/03
Posts: 8006
Loc: Rogue River, OR
You don't want moly rings for nitrous. As Cab said use standard tension oil rings. How much nitrous are you planning on hitting it with?

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#2291989 - 04/22/17 07:04 AM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
dthemi Offline
master

Registered: 10/31/04
Posts: 2600
Loc: back in Georgia
Rings are getting thinner still. Most new production stuff is 1mm 1mm 2mm. The race stuff is even thinner.

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#2292205 - 04/22/17 03:18 PM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
HotRodDave Offline
master

Registered: 01/29/05
Posts: 9469
Loc: Kalispell Mt.
I am building a 5.7 eagle motor for my truck and the rings are paper thin and with 300,000 it still used no oil and there is no discernable bore wear when feeling it up, cross hatch right up to the top of the bore. One important thing though is the oil drainbacks on the outside of the head keep a lot of oil off the crank and therefore off the cylinder walls. A vacuume pump and good windage control can work towards the same end and the less oil on the walls the less ring tension needed.

On my 410 stroker I ran 1/16 rings low tension all around with a dykes 2nd ring and it has no blowby and no oil use at 11.5 compression on iron heads.

A nitrous motor may have slightly different requirements but I am no longer afraid of the thin low tension rings on the street or strip. I bet the hellcats are running a very thin ring also and giving you a warranty with it.
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#2292213 - 04/22/17 03:30 PM Re: Thin vs. Thick Piston Rings [Re: HotRodDave]
ek3 Offline
super stock

Registered: 06/04/12
Posts: 771
Loc: MYRTLE BEACH SOUTH CAROLINA
thinner ring sets are lower in drag yes. the important thing is to use a very good piston. this is because it is what keeps the rings seated "squarely" aginst the cyl. walls with all your new found pressure! good ring lands and a tight clearance and round cylinders will keep things from leaking. je makes a hardend ring set for nitrous and a great piston . I am biased to the mahle brand products myself. ditto on std. tension oil rings. and pleanty of end gaps...


Edited by ek3 (04/22/17 03:33 PM)

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#2292228 - 04/22/17 03:49 PM Re: Thin vs. Thick Piston Rings [Re: PurpleBeeper]
EV2Bird Offline
On Vacation

Registered: 06/23/14
Posts: 2956
Loc: Kansas Roads Between 0 and 140...
The newer ring packs are awesome but as mentioned it requires some very good modern machine work, and the new ring packs are not cheap either $300 and up.

After the last 3 builds being with the .043 .043 3mm rings im doing a std. 1/16 std. tension the drag is almost bothersome, with the thin ring packs and tight fitting pistons I could turn the assembly by hand on the crank snout easily.

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#2292289 - 04/22/17 05:31 PM Re: Thin vs. Thick Piston Rings [Re: EV2Bird]
MR_P_BODY Online   content
Master

Registered: 06/13/03
Posts: 50340
Loc: Romeo MI
Being that the blocks are harder now days you can
put in thinner rings and a bit less tension on
them.. try to do this 40 years ago and you would
have a 1/8" or deeper ring groove.. better quality
parts on all the stuff now days.. hell 40 years ago
a long life on a engine was 100K.. now days thats
just broke in... LOL
wave
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