BigRich954RR

iTrader: (1)

If building 2 engine that both come to 402 Cube one with 4.125 bore and one 4 inch bore. which one will put less stress on head/head studs and gaskets.

i know everything will not be the same. trying to build a smaller cube engine around 402 ci or stock 370 but thinking add ci will make my goal little easier.
to push 18-20 psi of boost into. trying to pick the best way to build a ls2 motor to handle it

keep stock sleeves if staying with 4inch bore but thinking they will flexs alot under pressure. then dry sleeve or wet sleeve ls2 block to add strengh and able to do 4.125 with stock stroke crank or 4 bore with 4 stroke. thats alot stiffer

also better to have 20psi of boost at 6500-6700 rpms with power maxing near there or rise the max rpms to 7000-7400 with boost around 16-18. if both made same power just at different ways. which should lower cylinder pressure. but stress the moving parts mor

TT632

iTrader: (3)

For equivalent pressures the larger bore with have a greater force acting against it, F=P*A. For a comparison a 4.030" bore will have an 1.5% additional force acting against the head and into the bolts/studs.

Old SStroker

Are you assuming that both engines produce the exact same power curve? If not, it would be very diffucult to figure the difference, and any comparison would be virtually meaningless.

FWIW, head gaskets see total cylinder pressure while the head studs/bolts see loads resulting from the cylinder pressure times the bore area. You might conclude that loads from the cylinder pressure times the gasket area (diameter times thickness) on the larger bore gasket on the 4.125 are less than the loads on the smaller bore gasket. If the smaller bore gasket was about .002 thicker and the cylinder pressure was the same for both the smaller bore gasket would then be more highly loaded.

The point is that there only minor differences and other factors are much more important.

I suggest that the LS9 does not have a smaller bore than the LS7 because of this thread's subject, but for block durablility.

BigRich954RR

iTrader: (1)

i know everything will not be the same. trying to build a smaller cube engine around 402 ci
to push 18-20 psi of boost into. trying to pick the best way to build a ls2 motor to handle it

dry sleeve or wet sleeve ls2 block to 4.125 with stock stroke crank or 4 bore with 4 stroke.

also better to have 20psi of boost at 6500-6700 rpms with power maxing near there or rise the max rpms to 7000-7400 with boost around 16-18. if both made same power just at different ways. which should lower cylinder pressure. but stress the moving parts more.

racer7088

The smaller bore engine will be easier to keep head gaskets on but its a small difference as Oldsstroker says.

Stang's Bane

iTrader: (22)

FWIW a stock stroke 4.125 bore engine is ~387-388 CI. I am sure you already knew this, but others readign the thread may not. Good luck.