I took my 1.3 block to have it bored and they went to 30 over and marked it 75mm.  My question is shouldn't 30 over be 74mm and if so what would 75mm work out to?  Thanks. c

I'm a little puzzled by your question - stock a G13 has a 74mm bore (73.97~73.99).  Suzuki does not offer a 30 thou oversize piston (only 0.25mm & 0.50mm - if I'm correct, roughly equivalent to 10 & 20 thou oversize) which would work out to 74.220~74.230 & 74.470~74.480 respectively (these figures are being transcribed from the FSM) - that would make your 75mm bore roughly 40 thou oversize.

I'm also puzzled as to why you're asking the question - did you not purchase the pistons first and have the block bored to suit?

I took my block to the machine shop and they bored it to 75mm to clean it up and told me that it was 30 over. As you said I could not find 30 over pistons and ring till I found a set on eBay. When I called the guy who had them he also told me 75mm bore was also .30 over stock. I'm really hoping I don't have the wrong pistons coming.  Thanks for the help. c

I'd say you went about it the wrong way - if you bore the block and then buy the pistons you run the risk of excessive piston to wall clearance.

Step 1 - MEASURE the block.
Step 2 - Purchase the piston & ring set
Step 3 - Bore to suit the pistons.

Unless the block has suffered some sort of trauma, the machine shop should be able to 'mike' the block and tell you what size pistons you need, based on the difference in diameter between the worn & unworn portions of the cylinder wall - they should also have given you the same advice I'm giving you now.

What I've just outlined is not always possible - but even when it's not - the machine shop should be able to guide you.  I have a 1.3 block here (consider it a spare that I picked up a few years back) where the engine dropped a valve in the #3 bore, and the valve got bounced around some and that one bore has some pretty good nicks in the cylinder walls - there's no way to measure the depth of those nicks, although an experienced machinist can "guesstimate it" with a finger nail.

My machinist has already told me he thinks a 30 thou oversize will work, and given me the option of boring to 30 thou or sleeving that one hole and boring to whatever I need, but he's not going to bore unless I have the pistons for him to measure.

Thanks for the help Ford,I guess when I get the pistons in I'll take it all back to the machine shop and put it in his lap as to if it's a go or not. c