
Flow Testing
Mondello
Technical School
Want
to learn how to port heads from the master
himself?
Joe teaches a hands on head porting school
out his facilities in Paso Robles, CA. The
five day, nine hours per day, course teaches
you the theories behind porting and shaping
cylinder heads. Learn to use top of the line
equipment, including the 620 Superflow Flowbench
and a computerized cam profiler. You'll also
learn how to select the proper cam, intake,
and carburetors to achieve maximum results.
Food and lodging provided. He's also got a
Davenport small engine dyno for testing Briggs
and Stratton engines, for you go-cart and
junior dragster fans.
For more information:
http://www.mondellotwister.com/
1-888-MONDELLO
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We
decided to have a reputable and independent source
test the heads for us. Who better than legendary head
designer Joe
Mondello. For those of you who don't know, Mondello
is arguably the worlds most definitive source on cylinder
heads. Having worked for Caroll Shelby back in the
'60's, then helping design GM and Olds heads for most
of his career, Mondello heads have been on everything
from Lemans winning Cobras, to the NHRA and IHRA record
holding Top Fuel dragsters. Today Joe passes his knowledge
of cylinder head and engine building through the Mondello
Technical School, a fully equipped facility based
in Paso Robles, Ca (see side bar). Joe was gracious
enough to offer his services and facilities so we
could put together this article. In fact, what may
be more remarkable than Mondello's cylinder heads,
is his patience. Due to the problems mentioned above,
we rescheduled the test day at least six times over
as many months, mainly due to one manufacturer promising
heads but not delivering. Fortunately Joe accomodated
our schedule and we finally made it down to the school.
Joe and his assistant Shawn Corchero spent the day
with our Technical Editor Jim Langley, and we finally
got all the heads tested.
Test Procedure
We
felt it was important to test exactly what the consumer
would receive, so we explicitly specified the heads
must be in box stock form, no porting, polishing,
or additional machine work was allowed. The only modified
heads we tested were some of our home ported stock
heads, to see how they fare against the aftermarket
heads. All the heads were tested on a state of the
art, industry standard, Superflow 600 flowbench. Each
head was tested at a standard pressure of 28-in. of
H20. To simulate actual transitions, the intake side
was fitted with a clay lip, and the exhaust port was
fitted with a 1 7/8" diameter pipe, approx. 4" long
with a 90 deg. bend. The bore size used was 4.030".
The end chamber was tested on each head. Both the
intake and exhaust side were flowed in .100"
lift increments, to at least .600", or until
max flow was reached.

The
head fixtures: note the clay lip on the
intake port, the 1 7/8" header tube
on the exhaust side. The head sits on a
4.030" bore fixture.Inside the bore
is a honeycomb fixture to measure "swirl"
of the intake air as it exits the intake
valve.
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Shawn
Corchero of the Mondello Technical School
runs the Superflow 620 flowbench or us.
Testing over a dozen heads took about eight
hours.
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Fixture
used to measure intake air swirl into the combustion
chamber. |
Swirl
An added feature was this computerized intake port
swirling attachment,
which
measures the velocity and direction of airflow into
the combustion chamber. The use and value of swirl
numbers are still being researched, and while we
got numbers for all the heads we tested, we don't
know how to interpret them. The theory is that high
swirl numbers (rpms) offer better fuel distribution
and increase combustion chamber burning efficiency.
However, as the data shows, some of the best performing
heads in terms of flow, had seemingly poor or inconsistant
swirl numbers.
The stock heads, as well as the GT40X head, had
high swirl numbers. Keep in mind also that a flow
bench is only measuring dry air flow, so there may
be other factors involved affecting swirl when a
true air/fuel mixture is passed through the head.
The
Heads
We split the heads up into three categories, simply
to allow us to organize the results. Once
again this is not a complete listing of all the
heads on the market. However it does cover the vast
majority of popular heads.
Stock
(Factory castings, any size valves)
|
Street
(Valve size up to 2.02"/1.60")
|
Strip
(Valve size greater than 2.02"/1.60")
|
Stock
5.0 (E7 casting)* |
Edelbrock
Performer / RPM |
Trick
Flow R Series |
Stock
289 (C6 casting)* |
Holley
Systemax |
Edelbrock
Victor Jr* |
Home
ported 289 (C6 casting) |
Brodix
5.0 |
Brodix
Track 1 |
Stock
351W (D0 casting)* |
World
Windsor Jr. |
|
Home
ported 351 W (D0), stock valves |
World
Windsor Sr. |
|
Home
ported 351 W (D0),
Chevy valves |
Trick
Flow Twisted Wedge |
|
Power
Heads 289 (C6) |
Ford
Racing GT40X |
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Ford
GT40 P* |
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*Heads
marked with an astericks are ones which we did
not test at the Mondello technical school, but
obtained data from another reliable external
source.
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Stock refers to a factory cast head. We chose
the most popular factory castings. To determine
the value of home porting a stock head, we also
threw in a home ported 289 and 351W head, both done
by editor Jim Langley.
Street: This is the really the category of
interest as it consists of the most popular aftermarket
replacements. Street is a generic category, but
we defined it by aftermarket castings with valves
no greater than 2.02"/1.60".
Strip: This category consists of heads with
valves larger than 2.02" / 1.60", and
heads which may require custom modifications, such
as headers. However the heads in this category are
offered completely assembled and machined. If we
had the time we would have added a Race category
which would cover the top end heads, such as the
Edelbrock Victor, Brodix Neal, and Ford Racing Yates.
However testing those heads becomes difficult since
they are offered bare and require machining. Not
to mention that rarely are the heads used without
any porting work.
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