replacing the piston rings on my 455. do i need to break in the motor at all? use break in oil? or just start it up as if nothing is new?
Short answer, no, not if it is only new rings. Break in oil (typically loaded with ZDDP and made from mineral stock) helps metals with contact friction, like a flat tappet cam and creates a "sacrificial" barrier at a molecular level on the wearing/load bearing surface. Sort of a "surface hardening". You want the rings to have friction as that is how the high points of the cylinder hone marks are "knocked down". Break in oil will not hurt, but it will not do anything significant for ring break in. (it will provide protection to cam, tappets and valve train wear points, for a while) When in doubt, run the break in oil. But if you have been running high ZDDP oils, you should be fine without the break in oil. If you are running synthetic, switch to mineral/break in oil for to seat the rings. And, you need to run it to warm up, let it cool, then start, warm up and take it out and do half a dozen moderate pulls, (like getting on the freeway or passing someone) to seat the rings, and then you should be good to go. No need to change the oil, just drive it normal oil change interval.
thanks larry, that was helpful one more question, ive been having a heck of a time finding new rings for my motor because it is bored .20 over and everyone has discontinued the .20 over ring sets. i found some place in NJ that said they have a set, i just received them, but the end gap is about .047 (in the cylinder) and the old ones are about .025. is this eng gap too big?
https://www.summitracing.com/parts/slp-e-243k20/make/buick https://www.summitracing.com/parts/hsn-661020/make/buick
thanks matt, i tried T.A they dont have anything. the sealed power number i have is E289K-20 which i cant find anywhere. im a newbie at this, but the bore size you posted is 4.145 then .02 over bore. i need 4.312 then .20 over bore or 4.332 total. (am i wrong?)
Your issue also in finding rings at .020" over is there width! You may need to rebuild the motor with new Pistons just for the sake of being able to get rings, and of course if your going that far you might as well just overbore it the added .010" to get it to .030" over and then have a better selection of rings.
Hastings Manufacturing Company 325 N. Hanover St. Hastings, MI 49058 USA +1 800 776 1088 info@hastingsmfg.com
The only thing I have been able to turn up would be if you can find a old TRW set of T8265M - std rings. These are for a 4.342" Bore and would start you off with a .010" gap from what I can tell. The next best ring set would be a Sealed power set R-9224+.005" for a Bore of 4.325" which would start you off at about a .007" gap Both of these sets are double Moly and 5/64 5/64. And 3/16".
Tomahawk... T.A no longer stocks .020 over rings. They were my first try Stevem.. this is a re-ring, not a fresh bore. So everyone is saying that moly wont seal, and I should use cast iron, but if I cant find any I'll maybe try these, you think i should do the smaller gap (.07)
Modern moly rings are prelapped so if things where freshly rebuilt the term break in applies to the cylinder wall finish, not the rings!! Since your bores are used if they still show signs of the Hone pattern then your good to stuff in new Moly face rings, if not then get or borrow a 320 grit ball Hone and run it up and down each Bore 4 times, then wash the hell out of each Bore until surgically clean, then lube the walls up with very very light oil like 3 & 1, assemble the motor and fire it up. Here's how noted engine builder David Vizard prep's his fresh cylinder walls.
Stevenm. I actually did that already (ball honed the glaze off the walls). The engine was rebuilt only 3 years ago and the cylinder walls still have a good cross hatch. So if you think I could get away with a set of molly rings, which set would you go with those trw, or sealed power?
You want to go with the set that starts off being closest to the ring gap that the Bore size calls for. The more you need to file any ring, the more it goes out of round!