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Discussion Starter · #1 · (Edited)
Who has seen these heads off the car? Does anyone have pictures of the intake and exhaust and side by side with a Navi or pre-03 head? What's the flow on the stock 03 heads intake and exhaust v/s stock Navi and pre-03 What about the FR500? - John

According to www.modularperformace.com, my Extrude Honed Navi heads flow:

Lift 25* 28*
0.1 91.3 97.3
0.2 167 177.5
0.3 214.9 228
0.4 229.9 247.1
0.5 244.4 258.8
0.6 247.4 262.1

Are these good flow numbers? How do they compare to the flow numbers of the FR500 and 03 Heads?

I did a small bit of polishing to my heads, but haven't had them flowed again.
 

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I don't have flow numbers, but am interested. I thought they were Navigator heads and cams.
 

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03 heads are different. Best flowing 4V head yet.
 

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Discussion Starter · #6 ·
Thanks Chris! Yeah, send the pictures when you get a chance. Are the valve sizes the same? I hope they are because I just ordered Ferra valves in stock sizes, and if 03 heads are better I'm getting a set. - John
 

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And the 03 heads susposedly flow just as good if not better than the FR500 heads from what I've read. I'd guess they used alot of the FR500 head design in the 03 head. Wouldn't be the first time. The 5.0 GT40 heads ending up powering 5.0 Explorers years down the road.

The Aviator and Mach 1 have the same heads, I think the Maurader uses them too. The exhuast cams are the same, the truck cam. But I think the intake cam on the 03 is different.
 

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Valve sizes

Take your flow numbers at 28" and divide by the square inch of valve area minus the stem area. That will give you CFM/sq in. That is the basic criteria of a better head.

A sewer pipe gives good flow numbers. 96-100CFM/sq. in. is a reasonable number. 110-120 CFM is excellent. It is important that the valve lift point is below peak flow. Peak flow numbers are meaningless. //Michael
 

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IWRBB said:
The Aviator and Mach 1 have the same heads, I think the Maurader uses them too. The exhuast cams are the same, the truck cam. But I think the intake cam on the 03 is different.
The Navigator and the 03 Cobra use the same cams, both intake and exhaust.
 
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