Ring gaps
Thread Starter
Pro
Joined: Nov 1999
Posts: 509
Likes: 0
From: lantana,fl.
Ring gaps
Ring gap question?
Instructions say " bore x .0045 top ring
" bore x .0050 2nd ring
For street strip use.
I have a 4.155 bore math comes out to top .0187 top .020 2nd ring
Engine builders say 18thou top 14 2nd
What gives??
How come the 2nd ring gets wider, top ring is ok.
Instructions say " bore x .0045 top ring
" bore x .0050 2nd ring
For street strip use.
I have a 4.155 bore math comes out to top .0187 top .020 2nd ring
Engine builders say 18thou top 14 2nd
What gives??
How come the 2nd ring gets wider, top ring is ok.
Pro
Joined: Mar 2002
Posts: 511
Likes: 0
From: St. Louis MO
I went by the instructions, I figured the ring manufacturer knows best about how much thier rings will grow. Typically if you have the better rings (not cast rings), then top ring is a chrome alloy with a plama coating, the second ring is typically a cast ring and then the chrome oil ring pack. The difference in the numbers your given and what the manufacturer states have more to do with the materials they use.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by 442olds
I went by the instructions, I figured the ring manufacturer knows best about how much thier rings will grow.
RACE ON!!!
Burning Brakes
Joined: Feb 2005
Posts: 894
Likes: 91
Originally Posted by 74droptop
Ring gap question?
Instructions say " bore x .0045 top ring
" bore x .0050 2nd ring
For street strip use.
I have a 4.155 bore math comes out to top .0187 top .020 2nd ring
Engine builders say 18thou top 14 2nd
What gives??
How come the 2nd ring gets wider, top ring is ok.
Instructions say " bore x .0045 top ring
" bore x .0050 2nd ring
For street strip use.
I have a 4.155 bore math comes out to top .0187 top .020 2nd ring
Engine builders say 18thou top 14 2nd
What gives??
How come the 2nd ring gets wider, top ring is ok.
Team Owner
Joined: Sep 2003
Posts: 88,393
Likes: 2
From: eville in
Originally Posted by GOSFAST
New rules!! More propaganda? Maybe, but personally we send all street units out still with .018" top and .014" second (file-fits). No problems. Mfr's. claim better ring seal from top ring with wider gaps on second one. However, having a SB (N.A.) make 736HP on pump-gas (89 octane) we figure we have plenty of ring experience behind us, therefore we don't buy into their theories just yet. It may change but not now. Thanks, Gary in N.Y.
Thread Starter
Pro
Joined: Nov 1999
Posts: 509
Likes: 0
From: lantana,fl.
Originally Posted by GOSFAST
New rules!! More propaganda? Maybe, but personally we send all street units out still with .018" top and .014" second (file-fits). No problems. Mfr's. claim better ring seal from top ring with wider gaps on second one. However, having a SB (N.A.) make 736HP on pump-gas (89 octane) we figure we have plenty of ring experience behind us, therefore we don't buy into their theories just yet. It may change but not now. Thanks, Gary in N.Y.
Sorry I left out some info,pistons are ross flat top forged,rings are JE/SRP
file fit. Instructions talk about different style rings and shapes but the gap measurements cover all applications. I pretty sure the top ring is moly and second is iron.
So do the gaps need to change? I don't want to bind anything,and I don't want a bug fogger either!!!
Burning Brakes
Joined: Jan 2003
Posts: 755
Likes: 32
From: Roswell Georgia
Originally Posted by 74droptop
Instructions talk about different style rings and shapes but the gap measurements cover all applications. I pretty sure the top ring is moly and second is iron. So do the gaps need to change? I don't want to bind anything,and I don't want a bug fogger either!!!
Normally, file-fit ring gap recommendations usually will vary somewhat by manufacturer, e.g., Total Seal vs SpeedPro, as well as the ring material, e.g., ductile iron versus cast iron. For performance-oriented engines, the second ring's gap is usually smaller than the that for the first ring. Scoggin-Dicky's parts catalog has an excellent piston ring end gap guide that's too long to reproduce here. You can get it along with other good tech tips for the DIYer's by following this link for a free catalog.
Hope this helps!
- Greg Smith, Perpetual Corvette Mechanic
Pro
Joined: Dec 2001
Posts: 708
Likes: 0
From: Renton Wa
My understanding of why they are now requesting that the second ring be gapped larger than the top ring is to simply allow those gasses that escape past the top ring a faster exit to the crankcase. To me it does make sense. Under high rpm if there is not enough gap on the second ring then pressure will build up and cause the top ring to lift. Besides if the gas gets past the top ring, then whats the use of that gas anymore. It's not going to aid in combustion, so help it find it's way out of there so it does not hamper with anything else.
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Cruising
Joined: Oct 2005
Posts: 12
Likes: 0
just be certain u have enuf end gap. very small power loss with bigger gap. gap shrinks as temp increases,insuf gap and ring ends eat grooves in block. common error usually most obvious in #3 hole,if ur new eng is coloring #3 plug black u know why. if in doubt ASK MFR.
Large Impressive Member
Joined: Jul 2003
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Go with the piston manufacturer's specs for your bore, application, fit and end use. They know how much their pistons will grow and how hot they'll get for a given purpose and so what gaps are needed. A bit too much gap is much better than not enough.
