I was asked," whats the difference between 2,4, and a splayed bolt block" on a normal chevy engine with 4 bolt main caps the caps look like this, notice the front cap is a two bolt main cap which is normal even on four bolt block where all the other caps have four bolts the better machine...
garage.grumpysperformance.com
factory OEM blocks are very thin wall casting's
the aftermarket blocks are cast of better material and made much thicker.
HOW FAR CAN YOU BORE A BLOCK? before you begin to have a engine block bored more than about .030 over size its a good idea to have the blocks bore walls sonic tested Have your machinist sonic check the block before you bore it. calculate the remaining bore wall thickness, and if its not thick...
garage.grumpysperformance.com
the answer depends on what your intending to do with that engine build and your budget.
think through your choices carefully.
chevy rates the two bolt SBC blocks at 350hp, but everyone has seen two bolt blocks built to produce 450 hp,
and stand up to that power level for short term stress.
the stock two bolt main cap block works ok up to about 400-maybe occasionally 450hp, if its only run hard occasionally.
adding splayed main caps aids the lower end rigidity, but its likely to cost you over $600 in parts and machine work costs
and might allow that original block to handle 500hp-550hp
(yeah I hear all the screams about guys who swear they build 500 hp sbc engine with two bolt main caps all the time)
theres a huge difference between hitting 6000 rpm plus occasionally vs regularly, and pushing 500 hp every once in awhile,
and running an engine hard/frequently at that power level like a dirt track cars engine! STRESS IS CUMULATIVE
if your intention is to build a daily driver , get main cap studs and use the block,
if your intention is to run the crap out of the engine added splayed main caps and spending $600 plus on caps and machine work might make sense, if your goal really exceeds 500 hp or you want a heavy use of nitrous buy a
Dart or BOWTIE 4 bolt block
DART blocks are built with better quality cast iron, higher nickel alloy and have much thicker castings
yes you'll constantly see videos showing stock blocks built to very respectable power levels,
but again, stress is cumulative, and the longer the blocks stress level exceeds about 400 hp and the higher the stress,
the more likely it will eventually fail, I've sure seen plenty of guys that had spun bearing's or cracked heads within weeks of boosting power levels on stock block's
again AFTERMARKET DART blocks and SCAT or similar 4340 FORGED rotating assembles ,
have FAR greater strength and can regularly handle 600-700 hp