Drag Illustrated Issue 151, December 2019 | Page 59

DART BLOCK CHART
BLOCK PN BORE DECK
HEIGHT MAIN
CAPS MAIN
JOURNAL PAN
RAIL*
SHP Iron
SHP Iron
LS Next Iron
LS Next Iron
LS Next SHP Pro Iron
LS Next Aluminum Skirted
LS Next Aluminum Skirted
LS Next Aluminum
LS Next Aluminum 31867111
31867211
31837111
31837211
31867112
31947211
31947221
31937212
31937121 4.00
4.125
4.00
4.125
4.000
4.125
4.125
4.125
4.000 9.240
9.240
9.240
9.240
9.240
9.240
9.450
9.240
9.450 Steel
Steel
Steel
Steel
Steel
Steel
Steel
Steel
Steel Std.
Std.
Std.
Std.
Std.
Std.
Std.
Std.
Std. LS
LS
Conv.
Conv.
LS
LS
LS
Conv.
Conv.
Up from that is the LS Next iron non-skirted
race block, which uses a conventional 4-bolt,
splayed cap in the center three and oil pan rail
position that allows kick-out oil pans where chas-
sis clearance is available. This block also features
220 BHN material and will accept up to 4.200-
inch maximum bore diameter. Additionally, the
LS Next iron non-skirted race block is capable of
receiving the LS Next 2 upgrade, which incorpo-
rates larger main caps and 1/2-inch main studs.
This is the ultimate cast-iron LS Next block for
the highest horsepower applications.
Moving into alloy materials, the LS Next alu-
minum blocks are available in either skirted or
non-skirted configurations. All Dart aluminum
blocks use ductile iron sleeves and extra-thick
cylinder walls. At the top rung are custom billet
aluminum blocks that are for the highest tiers
of racing. Enhancing these standard cast block
offerings are multiple custom options such as
raised cam locations, cam journal sizing, lifter
bore bushing/resizing, stroke clearance, piston
oil squirters, 1/2-inch main studs and many more.
The main advantage to aluminum blocks is
their reduced weight. A typical iron non-skirted
LS Next block will weigh in at 227 pounds, while
an aluminum version of that non-skirted block
will come in at between 115 and 127 depend-
ing upon bore size. This offers an immediate
100-pound weight savings.
Dart was the first to eliminate the deep skirt
with the iron LS Next block in an effort to mini-
mize windage issues that have shown to be a sig-
nificant impediment to making high rpm horse-
power. The goal with the non-skirted block was
to create a pan rail position similar to the original
small-block Chevy.
All Dart LS Next blocks employ a priority main
oiling system. This is a critical upgrade because
the factory LS oiling route forces the oil through
the hydraulic lifters on its way to the main bear-
ings. Dart’s priority main circuit creates a sepa-
rate channel that directs oil equally to both the
mains and lifters, ensuring that lubrication is
unrestricted to the mains and connecting rod
bearings
The other major Dart design improvement is
the 0.375-inch longer cylinder bore sleeve length.
December 2019
On the surface this might not sound like a big deal,
and for stock stroke engines, it isn’t. However, if
you’re contemplating investing in an aftermarket
block, why not add some displacement at the
same time and keep the piston in the cylinder
bore at the bottom of the stroke.
When adding stroke, this increases the dis-
tance the piston travels. A long stroke LS package
will tend to pull the lower half of the piston skirt
completely out of the bore at bottom dead center
(BDC). This forces the piston to rock over center,
which can damage the piston skirt. Dart’s longer
sleeve length prevents this issue, yet there is still
plenty of clearance for up to a 4.100-inch stroke
on any of the LS Next blocks.
Speaking of bore size, LS Next aluminum and
cast iron blocks start at 4.00in and 4.125in ver-
sions, and can be bored as large as 4.185. The LS
Next iron, non-skirted race blocks can be bored as
large as 4.200in while the cast-iron SHP blocks
have a max bore of 4.185in. An LS Next block will
offer a minimum of 0.275-inch wall thickness at
a 4.185-inch bore diameter.
Moving to the bottom side of the block, both
the iron and aluminum blocks use steel main caps
with the outer bolts splayed on the center three
caps to increase strength. On the skirted blocks,
these caps eliminate the need for the small, hori-
zontal bolts used on production LS blocks. The
Dart splayed cap design is intended to increase
the common area between the cylinder cavities to
reduce windage issues and maintain solid main
webbing without communication windows. Dart
also offers a windage tray that is designed to work
with the Dart splayed main caps.
Even with all these improvements, the Dart
LS Next blocks retain the OE provisions for the
stock LS front and rear covers along with the LS
pan rail bolt pattern. On the side of the block,
the stock LS four-bolt motor mount pattern has
been retained along with the Gen III bellhous-
ing pattern.
The LS small-block architecture offers plenty of
opportunity to make big power with an LS engine
and this new LS Next generation of Dart blocks
will make sure that the foundation is strong and
more than capable of making the kind of power
you have in mind. -JEFF SMITH
This production iron LS block reveals how the area
near the main webs is very restrictive and how this
contributes to windage problems especially with
longer stroke engines.
If your LS plan calls for boosted cylinder pressure,
all Dart blocks come with six head bolt pattern per
cylinder over the stock 4 bolts. If the additional bolts
are not needed, no special accommodations are
required – a stock head and gasket will work just fine.
Which main cap fasteners would you prefer? Stock
LS engines use 10mm (0.393-inch) fasteners while
the Dart block uses 7/16-inch (0.4375-inch) fasteners.
If big power is anticipated, Dart offers an upgrade to
½-inch (0.500-inch) studs.
Non-skirted Dart LS blocks can still accept stock-style
oil pans with the help of billet aluminum adapter rails.
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