Piston Ring End gap.
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Piston Ring End gap. I have a 98 block that was honed out .005. I have another set of of pistons that were flycut with total seal rings on them that have only 150 miles from another block that spun a bearing. Is it okay if I use these pistons and rings from the other block in the current block I have? I put the rings inside the bore and the end gap is about .028 where spec is .009 - .014. I guess it not safe to use these rings because it may leakdown too much? I dont know how forgiving it will be. Thanks guys!
Well, if you honed it .005 you may want to do more than check the ring gap. If your rings and pistons are for a stock bore you're in trouble. You might have excessive piston to wall clearance. Check that before you go any further. You might need new pistons, and with new pistons will come the proper rings. I'd take the pistons you plan to use and your block to a machine shop and have them check the clearances.
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I dont think you need new pistons just for a hone job. If they did any boring then yes but you cant bore a 98 block more than .005. I dont think they honed it .005 its just my guess because thats the max on it. They just cleaned up the cylinder walls. Im just not sure if that end gap is tolerable even out of spec... kinda stupid I Know.
I've rebuilt several tractor engines and such growing up as a kid on a farm. I've also built a few SBCs and I rebuilt my LS1. .005 can be a huge deal if you are dealing with a small bore engine like a LS1. Here are the specs for a stock bore/piston LS1.
Piston Outside Diameter at Size Point 3.8962 - 3.8969 inch
Piston Out-of-Round Service Limit 0.0007 inch
Piston to Bore Clearance Production 0.0007 - 0.00212 inch
Service Limit (Maximum) 0.0007 - 0.00212 inch Note: (Maximum)
If the bore to piston clearance is close you need to go with bigger pistons unless you want a "slapper" motor. Don't assume, always know!!!
Piston Outside Diameter at Size Point 3.8962 - 3.8969 inch
Piston Out-of-Round Service Limit 0.0007 inch
Piston to Bore Clearance Production 0.0007 - 0.00212 inch
Service Limit (Maximum) 0.0007 - 0.00212 inch Note: (Maximum)
If the bore to piston clearance is close you need to go with bigger pistons unless you want a "slapper" motor. Don't assume, always know!!!
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I wanted to add this also. If it was just a cleanup hone, ok that's what it was. BUT you still need to check your clearances. When a block is honed you still sometimes lose .001-.002 of material. If your motor was already on the high side of things you are way out and that would explain why you have stupid huge piston ring gaps.
PS. GM manual calls for ring gaps as follows
(Measured in Cylinder Bore)
Piston Compression Ring End Gap Production-Top 0.009 - 0.0149 in
Production-2nd 0.0173 - 0.0251 in
Piston Oil Ring End Gap Production 0.007 - 0.0271 in
Piston Oil Ring Groove Clearance Production 0.0004 - 0.00866 in
PS. GM manual calls for ring gaps as follows
(Measured in Cylinder Bore)
Piston Compression Ring End Gap Production-Top 0.009 - 0.0149 in
Production-2nd 0.0173 - 0.0251 in
Piston Oil Ring End Gap Production 0.007 - 0.0271 in
Piston Oil Ring Groove Clearance Production 0.0004 - 0.00866 in
Last edited by kossuth; Sep 3, 2006 at 02:01 PM.
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Verdad Gallardo Ok, also wanted to add this. Ring gaps are the way they are for one purpose only. Rings expand from heat. This is why you have to have a gap. The engineers that design the engines know that certain materals expand at a certain rate and thus build that into their models. The reason why nitrous motors and blower motors use a larger ring gap is because the heat generated is alot more. Street motors and NA motor tend to have tighter gaps than nitrous or forced induction motors for this reason. A ring gap that is too tight can actually bind up the ring and ***** up your cylinder walls. A ring gap that is too large will cause excessive blowby.
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The reason why the gaps are stupid big was because the rings were in another engine. I will check my clearances when I get to the shop but I am pretty certain it will be okay. This is the first time its been rebuilt so everything should still be within servicable specs. I'm just going to buy new rings and check my clearances. Thanks for the help!
