Hello,

I had an offer from a local mechanic to rebuild my LO3. He stated that he would bore my motor out 30 over for 1200.00 and stated it would give me 30 horses. Sounds impractical and expensive. What kind of gains can I aspect? Thanks in advance.

Not much you bore to clean the cylinders up, you stroke to gain power/ displacement.

Sounds astronomically high to rebuild a 305. Im still looking for someone to haul away my L03 for nothing. Shows you how much a worn out 305 is worth A new stock 350 shortblock from GM goes for less then that at some places.

FWIW, ideally with the same parts on each, the 350 could potentially make 15% more horsepower.

Never rebuild a 305. You only need to rebuild an engine if there's something wrong with it, like losing compression in cylinders or spun bearings etc. If your 305 is burning out, pick up a 350 and rebuild that, it would end up being cheaper in the long run anyways.

I agree. For $1200 you can get a new L98 shortblock. There is no point in spending money on a 305 when it costs the exact same (most times cheaper) to build a 350.