Im having my block (L98) bored .030 over. I'm putting in a set of new pistons. If i put in oversized pistons, do I use a standard ring or .030 ring? My guess is an oversized ring, but i just need to make sure. Could i keep a stock piston size and just use a bigger ring or is an .030 piston the "right' way to do it? Thanx.

 

You must use a .030 over size set of rings with the .030 over size pistons. You can't use stock rings on the oversize pistons, or stock pistons with oversize rings. They have to match.

When I did my last engine I got "file to fit" rings. These are slightly over the .030 size so you custom taylor the end gaps for less compression loss.

 

get the whole kit from TRW or SpeedPro. you can usaully get forged pistons bearings ring etc etc etc in a whole kit. i dont really think file fit rings are nessacary unless your running a very thin ring with alot or rpm and compresion. however when building you engine you will still have to check the ring gap. as for the file fit rings being oversize not quiet but close. there not truly oversize. they just dont have a clearance built into them. there desinged to be perfectly sized to each bore. so unlike a pistons which might actually be 0.0298 the ring is realy 0.30 overbore. this allows it to actaully stay round while closing the gap for better compresion and seal. this will help on 2 fronts. better ring seal usually leads to better vacum at idle and will help reduce oil consumption. also when gapping rings open the second ring up another 0.005 than the top one. the latest ring theory ive been reading alot on suggests that a larger ring gap improvesprimary compresion ring seal by keeping the gas pocket from forming under the compresion ring to start with. the larger ring gap allows the escapping cumbustion gas to get by. this of course improve ring seal and reduce flutter at high rpm. all of this will help promote HP and TQ production. At anyrate get in touch with a reputable engien builder like marcelli brother on harford road. or even pual hoage machine. there are booth reputabel shops that turn out good quality work. as for teh secondary ring gap there are varying thoerys. the data ive seen from sevral machinist seminars and the imorvments ive seen real world froma larger second gap point to the latter to be true. a larger secondary ring gap will help compresion. its basically and oil scrapper anyways. youve got my email i can refer you to sevral reputabel machine shops that do good work.