Skypilot797

Which combination is better for a NA build of around 550 rwhp?

A 427 with a 4.125" bore and 4 inch stroke?

Or a 427 with a 4.185' bore and a 3.875 stroke?

Hows the Dart sbc short block holding up for a 550 rwhp NA 427 build? Reason I am asking is I am shopping and seeing these offered at what seem very reasonable prices.

allblowdup

The normal ls3 block has issues boring them over 4.100 unless you get them sleeved. You can do a 4.065x4.125 stroke that works but the machine work needs to be good for that long of stroke and pistons made for that combo.

nobreaks254

iTrader: (50)

Cant tell which is better, but I'm just starting a 4.125 bore 427 with a sleeved LS2 block

WKMCD

iTrader: (2)

The shorter stroke MAY allow you to rev higher with lower piston speeds. With either bore there should be minimal valve shrouding so that's a wash.

It really depends how it's put together, how it's cammed and what intake configuration you're going to run as to which is better.

Just my $.02

QuickSilverNA

Do the 4.125 bore/4.000 stroke. Pistons are more readily available. If its a street car with hyd roller cam then your probably not going to turn over 6800-7000rpm anyways so the 3.875 stroke will be almost pointless.

Build the 4.125/4.000 combo and focus on getting some great heads. Engine is an air pump, gotta have good heads to make the power.

3.8redbird

iTrader: (3)

Dart makes and lsx block now? I know they have their gen 1 sbc (SHP and little M) blocks but besides the billet stuff I wasnt aware...

COPO9560

Original 427 had 4.251 bore and 3.76 inch stroke - back when over square was cool.

These days I'd go with the 4 inch stroke - parts are easier to come by and there is always room for an overbore later. For a street car, you might consider the larger bore and 4 inch stroke. Can't call it a 427 but 44x cubes would be a great engine with the right heads.