I'm looking at a couple of four bolt 350's '69 and '70 and know that one has already been bored .30 over. Am I good if I want to rebuild (bore) and machine again, or even stoke? What is the max advisable to bore a good '69 block? I've heard that .60 over is too much?My plan is to at some point build a strong 12 second motor for my '77 camaro and possibly spray at some point.

Thanks,

Tom

 

they bore 0.60 all day long.i have heard of 0.80,i think that is pushing it.dirt track cars are on a 0.60 over 350cubic inch limit and they turn 6500-7000 rpm's all night long and all season long.a couple might have issues but that's part of racing.i wouldnt be afraid of a 0.60

 

Some blocks can be bored more than others it depends on core sift and the quality of casting most 350s will eaisly go beyond .030(its not .3 )but to be safe especially with nitrous I would have it sonic checked. Remember one thing just bore enough to clean it up you gain very little increasing bore size.

 

.060" is too much unless you have the block sonic checked. Most all builders will tell you to stop at .040" unless you have the block checked. The ones on the dirt tracks are sonic checked and they still have problems sometimes. Seen one on the dyno that had almost $30,000.00 wrapped up in it and it left go on the dyno. Expensive explosion... The one problem you will almost definitely have with a .060" over is heating which will show up quickly on a street car with traffic.