Modifying the LS for more power is as easy as falling off a log, to a
point, then some tough issues arise, especially if you are building a
high-rpm race engine. But until you reach that point, the LS responds
nicely to boring and stroking, improved cylinder head flow and they
respond especially well to power adders.
The only real chink in the LS armor is that GM’s cylinder head
designers didn’t leave any room for a proper high-lift, high rpm
valvetrain. It’s essentially the same problem the Gen III Hemi’s have −
no room under the valvecover. The stubby LS rocker is just about
standing on end at lifts above .650?, and there’s not enough real
estate to install a longer pivot length rocker and shaft assembly that
provides good rocker geometry. Some companies like Mast Motorsports are
taking matters into their own hands and designing heads like its Mozez
that has a larger rocker area and uses an SB2 small-block valvecover.
But that’s okay, especially if you decide to build for torque instead
of rpm. The LS engine readily responds to stroker crankshafts with
corresponding cylinder heads capable of feeding the increased
displacement. The LS has always been thought of as a replacement for
the small-block because of the similar 5.7L displacement, but in
reality, the engine responds more like a big-block. You rarely hear of
anyone with a truck complaining that they want their old 454 back in
place of their new 6.0L LS, because he 6.0L tows almost as well with a
lot better fuel mileage.
Speaking of displacement, GM has built several production versions of
the LS ranging from a 4.8L truck engine to the 7.0L Z06 Corvette rated
at 505 naturally aspirated horsepower. They did this with two
generations of engine blocks Gen III ’97-’05 and Gen IV ’05-’11),
available in both aluminum and iron. GM even produced a front wheel
drive version, the LS4 that has a unique bellhousing bolt pattern, so
be aware of that one when scrounging the salvage yards for cores. Gen
III engines were built with three different bore sizes 96.01mm (4.8L
and 5.3L truck blocks), 99mm (LS1, LS2, LS6) and 101.6mm (6.0L truck
blocks). Gen III stock stroke cranks were 83mm (4.8L truck) and 92mm
for both LS1-LS6 and 6.0L truck engines.
The LS series of engines uses a cam position sensor that provides the
ECU with timing information. Part of this system is a reluctor wheel
attached to the crankshaft. It is important to take note of the
reluctor wheel tooth count as most Gen III engines (up to 9/05) used
24-tooth reluctor wheels and 58X-tooth reluctors for the Gen IV
engines. There’s actually much more involved than tooth count because
the reluctor wheel is ECU specific. How and where the cam position
sensor is mounted, and with which type sensor 1X, 2X or 4X, adds to the
confusion. If your customer is converting to drive-by-wire, it adds
another layer of complexity. We don’t have room to completely cover
this subject, but there is lot of information available on the LS
forums like LS1Tech, LS2.com and others. Just understand that this is a
critical consideration with any LS engine build.
In 2005 Gen IV engines were introduced with now recognizable
performance icons like the LS3, L98 and the awesome LS7. A couple of
things that could trip up the average engine shop is that some of these
engines came from the factory with variable valve timing (VVT) and/or
active fuel management. So do your research when building a stroker
engine for a customer and make sure you know what you are dealing with.
Gen IV blocks came in four sizes 96mm (4.8L and 5.3L truck), 101.6mm
(LS2, LS98 and 6.0L trucks), 103.1mm (LS3, L92 and L99) and 104.8mm for
the LS7. Stroke selection remained the same as the Gen III with 83mm
and 92mm, plus the addition of a 101.6mm stroke for the LS7.
Another LS block from GM worth mentioning is the aftermarket LSX iron
block with a raised cam and deck height that accepts bores and strokes
to 108mm x 114.3mm (4.25? x 4.5?). These blocks are capable of handling
2,500 hp with the proper rotating assembly, cylinder heads and power
So with a better understanding of the different LS engines produced by
the factory, let’s take a look at stroking them for more performance.
We contacted Horace Mast of Mast Motorsports for some advice as his
company is dedicated solely to engineering and supplying complete LS
engines to the aftermarket. His best advice is limiting the stroke to
101.6mm (4.00?) in any standard deck height LS block. (Horace says that
most of his engines end up with a 9.230? deck height after surfacing.)
This will provide up to 416 cid for an LS3 and 427 cid in an LS7. He
has built LS3 and LS7s with 4.100? stroke cranks, but says that the
have poor long-term durability, and he doesn’t recommend them,
especially for daily driven street cars.
The problem with strokes in excess of 4.00? in a LS motor is that the
piston skirt is not properly supported at the bottom of its travel,
causing a lot of rocking and premature wear. In fact, Mast’s 4.00?
stroke engines use specially designed Mahle pistons to minimize this
problem and to provide a more stable ring package. Horace maintains
that the same holds true when using the taller deck LSX block Mast
limits displacement to 454 cid even though 511 cid is possible. Even
then Mast warns its customers about using these engines as daily
drivers because there are too many compromises in the area of piston
Other companies like Flatlander Racing who sell K1 stroker kits for LS
engines agree with Mast on the 4.00? stroke for normal deck height
motors, but are more aggressive on the LS7 putting the limit at 4.120?
stroke and 4.250? for the LSX blocks.
Another issue with LS engines is making sure that your bore size is
compatible with the cylinder head you will be using. Most companies
selling stroker kits do a good job at listing what heads will work with
which kits. However, if you are unsure, take a little time to research
what combination will work for you. It’s just one of those quirky LS
things that you didn’t have to worry about with traditional 23-degree
So let’s look at what’s available in LS stroker kits from some of the
aftermarket’s top vendors. Prices vary widely from top shelf U.S. made
components to lower priced imported components. Another contributor to
price is the completeness of the rotating assembly, and whether it
comes balanced or not. You can piece together your own assemblies
sourcing a crank from supplier X and pistons from supplier Y, but by
the time you are done with ordering, shipping and deadlines, you are
money ahead sourcing a complete rotating assembly from a single source.
Virtually all of these kits contain forged cranks, forged rods and
pistons plus complimentary rings, bearings and pins.
Eagle has a large number of rotating assemblies for sale that cover a
wide range of displacements and compression ratios. Its kits for
standard LS engines feature 4340 forged cranks in 3.622?, 4.000?,
4.100? and 4.125? strokes, which depending on the block and bore size
can net engine sizes from 347 cid to 434 cid. They all use 6.125?-long
forged H-beam connecting rods with either Mahle or Arias forged pistons
in various compression ratios. They also offer 4.250?-stroke rotating
assemblies with 6.460?-long rods for GM LSX tall-deck blocks for up to
454 cid, and 4.250?-stroke cranks with 6.560?-long rods for World
Products Warhawk tall deck blocks.
Lunati offers engine assemblies for LS1, LS2 and LS6 applications in a
variety of bore and stroke combinations. All of its assemblies feature
Lunati Pro Series non-twist forged cranks and Wiseco Forged and
CNC-profiled pistons. They are available in the following
displacements: 347 cid, 383 cid, 395 cid, 408 cid and with a 4.125?
bore block − 427 cid. You also have a choice of the more expensive
I-beam or less expensive H-beam rods, all 6.125? long.
Scat breaks its LS rotating assemblies down into two groups: street and
strip and competition. They also offer these kits balanced or
unbalanced, you decide. They offer three different stroke 4340
crankshafts at 4.000?, 4.125? and 4.250? strokes. Two different rod
styles, forged 4340 H-beam and forged 4340 Pro Comp I-beam 6.125?-long
are included depending on the kit. Forged pistons, rings, pins and
bearings are also included. Displacements from 365 cid to 461 cid are
K1 is part of the Wiseco/JE/SRP piston group and has collaborated with
Wiseco to build a really comprehensive catalog of LS rotating
assemblies, plus they have the advantage of designing components as a
unit, which reduces mass and results in assemblies that are easier to
balance. The K1 cranks are forged out of 4340 steel, core-hardened and
nitrided for journal surface hardness. K1 connecting rods are offered
in two styles forged 4340 and billet 4340. They are weight-matched
within a gram and come with pin bushings for improved friction
reduction. The pistons are all forged lightweight Wisecos with metric
ring packages. K1 offers kits from stock stroke 3.622? as well as
4.000?, 4.125? and 4.250? stroke cranks. Rod lengths vary from 6.098?
to 6.365? depending upon stroke and compression height. Displacements
range from 347 cid to 471 cid.
Probe has divided its LS rotating assemblies into two categories its
Dominator series features lightweight forged I-beam connecting rods and
its Pro-Street series features forged 4340 H-beam rods. Both series use
forged SRS pistons in a wide variety of compression ratios with tool
steel pins for the Dominator kits. The forged Probe rods come in 6.125?
or 6.200?-lengths depending on the assembly. The forged 4340 steel
cranks are available in 3.900?, 4.000? and 4.125? strokes. All kits are
complete with rings, bearings and piston pins.
While these manufacturers are just a sampling of what’s available for
LS stroker kits, it gives you an idea of just how many combinations are
available so that you can build almost exactly what your customer wants
Going to really long strokes and huge displacements require the
aftermarket blocks mentioned previously. The choices are GM’s iron LSX
block, RHS’s LS Race Block and World Product’s LS Warhawk block. Let’s
look at GM’s LSX engine first introduced by GM Performance Parts at the
2006 SEMA show. The LSX is an all-new cast-iron racing block based on
the LS7 engine. It was designed with help from drag racing legend
Warren Johnson. It offers displacements ranging from 364 cubic inches
to 511 cubic inches (4.25? (108 mm) bore x 4.5? (114.3 mm) stroke) and
is capable of withstanding 2,500 hp. This block incorporates two extra
rows of head-bolt holes per bank for increased clamping capacity. The
six-bolt steel main caps are the same ones used on the LS7 engine. If
you can handle the weight penalty of an iron block over aluminum, the
LSX is a good value.
Racing Head Service’s (RHS) LS Race Block is cast out of A357-T6
aluminum with press-in spun cast iron liners that are available in two
bore sizes 4.125? and 4.165?. The raised cam position can handle up to
a 60mm cam core and a relocated oil galley provides room for a 4.600?
stroke crankshaft and directs oil to the main bearings first. Two deck
heights are available: standard (9.240?) and a tall version at 9.750?.
The RHS block is chocked full of other features like multiple engine
mount options, dry sump connections and access to the two additional
head bolt hold downs per cylinder.
World Products Warhawk LS Race Block is another max effort block
capable of handling huge power numbers. Cast out of 357-T6 aluminum the
Warhawk features beefy 1045 steel cross-bolted main caps retained with
massive 7/16? main studs and cross-bolts. The Warhawk comes in two deck
heights, a tall 9.800? and the standard 9.240? deck. Optional head bolt
hold-downs (two per cylinder) help seal combustion pressures on highly
boosted engines. Two bore sizes are available 4.000? and 4.125? and
there is room inside to clear a 4.500? stroke crank. Like the RHS
block the Warhawk has several engine mount locations.
As you can see there is virtually limitless ways to build a large
displacement LS engine. And when you consider the plethora of
aftermarket cylinder heads, intake systems, and power adders, it makes
sense that the LS engine is going to represent a big piece of any
performance shop’s business. We hope this brief look into LS stroker
engines has whetted your appetite to build a few large LS derivatives.
Hot rodders are stuffing these engines into anything they can get their
hands on because the combination of lightweight and big power is too
hard to resist. With very little effort you can get old fashion
big-block power in a tight little package.
To download stroker kit charts, click here (Stroker Charts.pdf)
For a complete list of stroker kit suppliers, click here (Stroker Suppliers.pdf)
LS Stroker Sources:
K1/Wiseco Performance Products
Eagle Specialty Products