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Magazine article - "Building a Late Model Hemi Stroker"

Posted: Fri Jun 04, 2010 1:40 am
by mart
Magazine article - "Building a Late
Model Hemi Stroker

I came across this and thought it might be
of interest to some people here. Some of
the informationis in the article is pretty
basic, but there's also some very useful
and 'very late-Hemi specific' information
too. Enjoy!

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Engine Builder Magazine

Building a Late Model Hemi

Enthusiasts have, over the years, found a
way to stroke whatever engine they could,
and some of the combinations have been
downright interesting.

By Bob McDonald

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”.

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

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

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.

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.

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.

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.

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

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.

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.

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 their's 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

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

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!

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. Look for the wrap-up to this article in
an upcoming issue of Engine Builder.
Pics 1,2 & 3 of 6

Additional Pics -"Building a Late Model Hemi Stroker"

Posted: Fri Jun 04, 2010 1:47 am
by mart
Additional Pics -Re "Building a Late Model
Hemi Stroker

Pics 4,5 & 6 of 6