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2010 Stroker Engine Guide: Building a Late Model Hemi Stroker

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What is the purpose of stroking a motor? The answer is simple: to
obtain more cubic inches. And in today’s economic times, it’s always
best to achieve “more” with less – as in less money. The key word to
many stroker enthusiasts today is “budget”.

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However, the word “budget” has a way of being interpreted
differently by different people. The original point of stroking a motor
with a bigger crankshaft is to keep the original block in order to keep
the expense down.

Enthusiasts have, over the years, found a way to stroke whatever
engine they could, and some of the combinations have been downright
interesting. As explained in Dave Sutton’s article, it’s amazing what parts are available. These days, late model engines are gaining popularity in stroker builds.

Steve Bowman, owner of S&S Mopars in  Winston-Salem, NC, came to me
with a personal request to help him build a stroker for his 1969
Barracuda. Because he and his wife, Sheila, have been drag racing for
years, Bowman was interested in an alternative restoration that could
be used both as his weekend cruiser and drag machine.

His shop specializes in a full line of restoration services and
parts distribution, including various Mopar engine builds from stock to
blown alcohol Hemis. So, while the idea of putting a Mopar stroker
under his Barracuda’s bonnet wasn’t all that surprising, why would we
choose a Late Model Hemi stroker?

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When compared to the Chevy-based LS engines and the late model
Modular Fords, conventional wisdom is that there’s nothing out there
for the Hemi. After doing some research, it did seem as if there are
only a few specialty engine shops that have dabbled in the Hemi market.
Where can you find aftermarket parts if you’re interested in doing it
yourself? In the spirit of discovery, we decided to try to answer the
questions many people have asked of us. We wanted to expose the Hemi
engine to the aftermarket, find some resources for aftermarket parts,
and see what kind of power potential we could pull from our
combination.

The Hemi

In 2003, Daimler Chrysler made an awesome move in the automotive
industry and reintroduced the Hemi. Originally introduced in 1951, the
“double-rocker shaft V8” made a lot more horsepower than the other
motors available at the time. Three different families of Hemis were
built between 1951 and 1971, from a 241 cid Dodge to the legendary 426
NASCAR motor of the late ’60s. However, during the fuel-saving ’70s,
Chrysler shelved the motor.

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Luckily, in 2003, the 5.7L Hemi returned in the Dodge Ram pickup. A
bigger version – the 6.1L followed in 2005 in several of the other
Mopar monsters.

Today, the 6.1L can be hard to find in a rebuildable state – and likely
to be quite pricey. The 5.7L is somewhat easier to find. After doing
significant research we managed to find several 5.7L Hemi engines
available to be purchased across the country.

Keeping in mind that you can purchase blocks, cranks and most of the
accessories you’ll need to build a Hemi stroker (including complete
crate motors) directly from Mopar, critics might ask why we didn’t just
do that. In the spirit of the project, we decided to stick to the
aftermarket and try to stick to a budget by rebuilding a 5.7L Hemi. We
actually found a used engine online at a Mopar Parts Web site for
approximately $500. It was tired and in need of a rebuild, but it was
complete.

Here is a quick rundown of our 5.7L Hemi engine. It came with a bore of
3.92? and a stroke of 3.58?, which yields a displacement of 345 cubic
inches. It has a block height of 9.25?, cross bolted mains, 6.25? rods,
85 cc combustion chambers, 1.65 ratio rocker arms, plastic intake
manifold with a 80 mm throttle body that is electronically driven,
9.6:1 compression, one coil pack per cylinder firing dual plugs, and
firing order of 1-8-4-3-6-5-7-2. In factory form this engine made 345
hp @ 5,600 rpm and 375 lb.ft. of torque @ 4,400 rpm.  

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It gets its name from the shape of its combustion chambers.
Hemispherical chambers allow significant advantages with regard to air
flow.

The design and shape of the cylinder head eliminates the valve
shrouding found on other designs such as the LS Chevy and Modular Ford.
These design advantages right from the start mean we have a potent
cylinder head for the build.  

That’s a good thing, because aftermarket Hemi heads have proven to be
impossible for us to find. Luckily, the stock heads were serviceable.
The stock valve sizes for the 5.7L Hemi are 2.00? intake and 1.55?
exhaust. A small amount of porting seems to yield high flow at low lift
with very little effort. After replacing the stock valves with 2.02?
intake and 1.6? exhaust valves from Ferrea, as well as some porting,
you can see the comparisons. See the flow bench data in Chart 1.

Of course, there are companies that offer CNC porting for the Hemi
cylinder heads, and that’s certainly an approach you can take, but to
keep with the budget build, we opted to do it ourselves.

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Since we already had our block to build our stroker, the next step
was to add the crankshaft. Callies Crankshafts in Fostoria, OH, offers
a 4.050? stroke crank that will fit either the 5.7L and 6.1L block.
This turns out to be a pretty slick fit when you do the math. If you
put it in a 5.7L, you’ll get a 392 cid motor. If you install in a 6.1L
you’ll yield 426 cubic inches. So, by installing the crankshaft in
either block you’re able to take on some of the Hemi heritage.

With this 5.7L combination we needed a connecting rod that was
6.125? in length. The stroker crankshaft has a rod journal size the
same as a small block Chevy, which is 2.100?. We decided to use a
complete rotating assembly. As with many stroker suppliers you can
order it with private label parts or nationally recognized brand names.
Our package included the Callies crankshaft and small block Chevy rods,
with Mahle pistons and rings with Clevite rod bearings balanced and
ready for assembly. A set of Federal-Mogul main bearings made sure the
rotating assembly kept rotating.

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Chrysler does offer its version of a 392 Late Model Hemi, but does
so using a 6.1L block. This engine has a bore of 4.055? and a custom
stroke of 3.795?. It is offered in two different versions from Mopar –
either a 525 hp or a 540 hp version. Both engines have 10.5:1
compression with other changes along the way for the horsepower
differences.

So, can we make 540 hp from our stoker Hemi? We obviously won’t have
the same bore and stroke, but we’ll still have the same cubic inches.

Remember three things when it comes to engine building: heads, cam and
compression. This axiom is true today and will still hold true
tomorrow. We will keep our engine at 10.5:1 compression for pump gas
reasons. We have ported the cylinder heads and you can see the
differences between the stock heads and our ported version.

Because we really wanted to cut down on valvetrain weight without
going to titanium, the Ferrea valves we’re using are top of the line
small block Chevy valves which are .100? longer and hollow-stemmed. We
also upgraded to a set of Ferrea’s beehive valve springs, which replace
the beehive spring found in the stock Hemi version.

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Engine manufacturers have started using this style of spring in late
model engines because they are lighter and as you compress them they
become more aggressive. They also take up less space, this means you
can run them with many hydraulic roller applications without all the
spring hassle and still have a lighter valvetrain weight.

We found there are only a few companies grinding camshafts for the late
model Hemi. After doing some math and taking into consideration the
head flow numbers with the amount of compression we would be running, I
knew the grind that I wanted. The problem was that no one offers it.
So, I contacted Trent Goodwin at Comp Cams, who took a look at the
numbers and, to my surprise, had a camshaft ground in two days. Comp
also supplied the retainers for our beehive springs.

My hat is off to Trent for the hard work in grinding the camshaft and
I’m sure that he’ll soon be making numerous grinds for different
versions of this stroker build.

Keep in mind that there still aren’t too many parts on the shelves
for the late model Hemi, although the market has stepped up to the
plate in the past couple of years with increasing frequency.

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Although many of the internal components were accounted for, there
were still several pieces needed to finish. By looking for a supplier
with a long history of service to my performance business I was able to
find many of them in one stop. Since we were building a modified engine
it was a relief to find that Elgin Industries provides a broad range of
products for the late model Hemi. We sourced the oil pump, timing kit,
valve guides, and pushrods from Elgin. In a project like this, customer
service is key, and theirs has always been awesome.

The Hemi’s oiling system looked pretty good in stock form, but we
were concerned about what may be available in the aftermarket. Moroso
has been in the oil control business for a long time and they offer
some nice pieces for the late model Hemi, including an aluminum pan and
pickup tube made for some serious performance applications. The pan can
be used for wet sump systems with an 11 quart capacity. Wait – did you
just read 11 quarts? Because of the design of the Hemi heads and the
amount of oil retained in the top end, this capacity is necessary.

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The pan includes additional features such as a bung for an oil level
sensor or for possible use as a location for an oil heater. It also
features built-in trap doors and baffles for oil control and a location
for an oil drain if used in a turbocharged application. We also found a
great looking set of Moroso machined aluminum valve covers. They are
coated with a “black crinkle” finish with the center of the valve cover
left in a machined form, and the look really emphasizes the Hemi
heritage in a modern design.

And we required modern sealing techniques to keep it all together.
We selected a complete set of Fel-Pro gaskets from Federal-Mogul for
our late model Hemi. The set includes everything from the one-piece
rubber oil pan set to their ordinary line of seals to a state of the
art MLS head gasket. We used Fel-Pro head bolts to replace the stock
torque-to-yield bolts used during manufacturing. For the rest of the
engine assembly we used ARP studs and bolts.

For our top-end, including the fuel system and the intake, we used
replacement Mopar parts because of their availability. However, in
keeping with the spirit of the build, we’re working on sourcing
aftermarket upgrades to the induction system. We’re still trying to
keep to some sort of budget!

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Dyno numbers were not complete at press time, but this engine is
coming together nicely, proving that even a stroker no one thinks is
available can be built using aftermarket parts, on a budget and with
great results.

To download stroker kit charts, click here (Stroker Charts.pdf)

For a complete list of stroker kit suppliers, click here (Stroker suppliers.pdf)
Keeping in mind that you can purchase blocks, cranks and most of the accessories you
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