I just put a Precision 72mm in my 306 cu/in 5.0L stock block and I'm wondering how much boost I can run in it? I know after 500HP the blocks tend to split, so I am concerned about that, it already made 329HP at the wheels before I put the 72mm in it! Any constructive feedback is appreciated!
Im in same position. Planning on 8lb to be safe. But from all research, getting the tune spot on is the biggest factor. Plenty of guys running in mid 500s to 600 stock bottom ends.
There is no hard limit on the stock block. It's just luck of the draw. That's an old wife's tale from decades ago when no one knew anything about tuning. These blocks aren't hand crafted works of art individually sculpted by a tradesman, they are mass produced sand cast pieces punched out quickly with a bunch of flaws in them. You have to be careful picking up a stock crankshaft, because it has so many unfinished casting ridges, it will cut your hands up. Some crack at 350hp, some are pushing almost 1000hp pass after pass. You are taking your chances either way, but if you want to do your best to keep the block from splitting, keep the RPM as low as you can, and get the best tune you can. My last engine went 10 years and 85,000 miles at 500 RWHP on nitrous (which is way harder on the engine than forced induction) before it had a bearing failure; block was fine.