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Flow Testing

Mondello Technical School

Joe MondelloWant 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:

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.

Shawn Corchero of the Mondello Technical School runs the Superflow 620 flowbench or us. Testing over a dozen heads took about eight hours.

click for larger image!
Fixture used to measure intake air swirl into the combustion chamber.

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.

(Factory castings, any size valves)
(Valve size up to 2.02"/1.60")
(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
Ford GT40 P*


*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.

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.

(Flow Results.
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