Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - over sized rings on standard pistons
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Old 12-12-2012, 05:10 PM
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painted jester painted jester is offline
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So you have it bored to .030" over and you hone and get a bore Gage reading larger and the ring gap is over tolerance with the rings you got for your pistons. you need a longer circumference ring to close the gap you then order .035" file gap rings and file fit! That is the reason most performance builders use file fit ring packs. For every .001 increase in bore size you get about .003+ increase in ring gap for Hasting rings!

What ever rings you get, you should ask for tech papers they are free, your Jobber can down load them for you! Different manufacturers have different recommendations for their specific designs!!

Your service books for Ford, G.M., etc. give you their specs, don't set aftermarket rings at Auto manufacturers specs they may differ a lot, and you can screw up your build! these specs I'm giving are for Hastings Only as examples and don't cover all Hasting rings either. The different make up of materials and expansion rates change the specs from ring set to ring set manufacturer to manufacturer

Jester

http://www.hastingsmfg.com/Master_Ca...er_Catalog.pdf

From Hastings Tech papers:
The chart below gives the proper oversize rings to install for various oversize cylinders.
CYLINDER BORE DIAMETER........................ USE RING SIZE
Std. to .010" ................................................ST D
.020" to .029" .............................................. .020"
.030" to .039" .............................................. .030"
.040" to .049" .............................................. .040"
.060" to .069" .............................................. .060"
.080" to .089" .............................................. .080"
.100" to .109" .............................................. .100"
.120" to .129" .............................................. .120"


CHECKING COMPRESSION RING GAPS
RECOMMENDED
AUTOMOTIVE COMPRESSION
RING GAP CLEARANCES
Cylinder .............................Ring Gap
bore Diameter............... Ring Gap Tolerance
1.0000" to 2.3624".......... .006 to .014
2.3625" to 2.9524".......... .008 to .016
2.9525" to 3.5424".......... .010 to .020
3.5425" to 4.3299".......... .012 to .022
4.3300" to 5.1174".......... .014 to .026
5.1175" to 5.9049".......... .016 to .030
5.9050" to 6.8899".......... .020 to .035
6.8900" to 8.9999".......... .024 to .041

An important fact to remember is that these tolerances are rigidly adhered to by the manufacturers and that the ring gaps are inspected in gauges accurate to .0001" at the cylinder diameter the ring is manufactured for. Any
increase in the diameter of the cylinder the ring is being used in, over the designated size, results in an increase of approximately .003" in ring gap for each .001" increase in cylinder diameter.

STANDARD BORE TO .010 TAPER USE STANDARD RINGS.

A common practice in racing applications is file fitting piston ring end gaps. Most Hastings Racing Rings are available in file fit (+.005") oversizes. Professional racers and high performance engine builders understand that the exact setting of the ring end gaps by file fitting is beneficial to obtaining the precise engine efficiency desired.
Today’s performance piston designs are moving the top compression ring higher for optimum performance. This creates even higher operating temperatures, therefore requiring a larger top compression ring end gap. Also, improved thermal efficiency of a hypereutectic piston alloy keeps more usable heat in the combustion chamber with less heat moving down through the piston onto the piston skirt and into the oil.



File fit high performance application:
Formula: bore x ring end gap factor = minimum ring end gap.

FUEL APPLICATION RING END GAP FACTOR:

Street Normally Aspirated .0065"
---------------------------------
Drag Fuel and Alcohol .0075"
---------------------------------
Street Nitrous, Supercharged .0080"
Street Towing; Circle Track .0080"
Unrestricted & Alcohol; Marine .0080"

Last edited by painted jester; 12-12-2012 at 05:17 PM.
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