Hi, I'm rebuilding my 4.3L Vortec from 2003 Chevy Astro Cargo Van. When I bought it a year ago it had ~26.000 miles. The engine was knocking and I couldn't get rid of that annoying sound - tried to clean up lifters through the push roads and by "seafoaming". It didn't work out, so I just decided to pull the engine out and rebuild it, because I also wasn't sure if that was the accurate mileage. Anyway, I disassembled the engine - it looked perfect to me. I sent it to the machine shop, they also said that it's in very good shape, they didn't bore it, just honed. So it appears that the mileage is correct. Now closer to the subject - time to rebuild the engine. Per service manual, the cylinder bore size is 4.0007"-4.0017". Most sources tell that in order to calculate top ring gap you have to multiply 0.004 per inch of bore for street applications. Which gives that well known 0.016" gap (either way if I use 4.000" or 4.0017" as a base bore, the formula gives me 0.016" - 0.0160068" gap). I bought first set of rings - Clevite MAHLE 41786, standard, since machine shop guy said bores are standard. Inserted a top ring, slightly pushed it with the piston, measured the gap and it was ~0.026". "Way to much" - I thought, but measured few other rings and put them in different cylinders - results were pretty much the same. I though that probably machine shop guys did something wrong. So I bought a set of micrometers and telescopic gauges. Measured bores - 4.0022". That still keeps us in the range of 0.016" (0.0160088" to be exact). Then I thought, well, perhaps bores out of round. So I bought a bore gauge and checked all bores - all perfectly rounded (variation in 0.0005" which corresponds to the production Out-Of-Round specs). Then I thought - maybe it's just a bad rings set. So I returned that Clevite Mahle rings set. I bought another one - Sealed Power E920K (standard) set and received it today. Checked the gap, it was 0.027" - 0.029" (depends on how deep you push a ring with the piston plus how perfectly perpendicular you do this). So it looks to me that the manufacturers are cheating by making such a large gap so the rings fit both cast AND hypereutectic pistons. In my case, I'm reusing my stock standard pistons. Now here is the question. What would you do - return these rings and buy "file to fit" rings and make 0.016" gap, or install these 0.028" rings? P.S. I found TONS of priceless info on this forum, thanks.