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4V Heads - which are better?

There still are no aftermarket heads for the 4V Modular, besides the FR500 heads from Ford.

Here is a list of the current offerings
  • 93-98 Cobra/Mark VIII heads (I believe they are the same head
  • 99-01 heads
  • Navigator heads
  • 03 Cobra heads
  • FR500 heads

With that being said, which heads are the best? Do some work better with blown applications? I have been told the 99 heads flow less but have more velocity than the early model Cobra/Mark VIII heads. I have also been told that the 03 heads are best out, they have rectangular ports instead of oval ports. Also, does porting help these heads much?

This seems to be a really good topic, and I hope some of you modular gurus out there can help answer the questions here, and possibly back up your answer.
 

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don't consider myself a mod motor guru. but i read just about everything i can get my hands on and listen to just about every conversation that i come across concerning them. so take this for a grain of salt....

have heard the same thing regarding the 98 heads vs the 99+ heads. that the 98 have more flow and flow potential, but the velosity on the 99's are superior. now I was once told by J.Stewart that that made the 98's better in all out race applications.
I don't know too much about the navigator heads. and I am only familiar with one car online that is running them.
have heard that the 03 heads are almost exactly the same to the fr500 heads. but haven't seen any of them side by side to compare. if its true i would like to compare prices....for future upgrades.
if the fr500 aren't the same I would say they are about the best out there. but like i said its all heresay....so the grain of salt applies.
 

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I would have to agree on Joe's comment about the '98 heads. We have a guy here who ran a 10.0 on his cobra with stock heads. Which proves to me that porting your heads vice hp gain is a lose situation. Unless of course, 10's are not enough.
 

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forgot this part. when i heard the part about the 98heads being better for race apps then the 99+ heads the fr500 heads weren't out yet....

food for thought.....TBP's SSO car is using fr500 heads.
 

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interesting I had no idea..... wouldn't the navigator heads require different exhaust manifolds? I would think that they would require a different intake manifold too.
 

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just for a reference, my 99s flowed 304I and 254E @.5. they were done by TEA. If I had the money to build an all out race car then I would invest in the best possible that would fit my intake. I just dont think that buying another set of heads and then having them ported is worth the cost.
 

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My navigator heads should be on the car in about a month or so on my 4.6. It requires a custom intake but I have been told over and over that my longtubes that were on my 96 cobra 4v heads will work just fine. Boss 330 did my intake. It is awesome. The heads are being ported to the max so I will let you know how it turns out. The differences between the FR500 heads and Navigator heads are supposedly negligible from what I have heard and from what Haywood said there isnt much difference I guess.
 

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This is from the giant 5.4 thread on the corral. The question was.. Which head, FR500 or Navigator would work best on a 5.4.


Lets start with the chamber...They both average 52 cc and have the same shape, So.... The same.
Intake port on the 5.4 head has a much larger port entrance and more volume. This added volume is needed with the added displacement or high rpm. The problem in a 5.4 head is the very flat floor and almost no short turn radius. This causes the air to "overshoot" the intake valves at high lift and high air speeds. This makes the port think the valves are smaller than they really are.
The FR500 head has a standard 4.6 size port entrance and fairly small volume. The improvement comes from a raised roof and floor with a real short turn, This helps the moving air to use more of the valve area. However the heads i have seen have a rough poorly formed radius and need some work.
The 5.4 has a thick divider in the exh port that allows coolant to flow through this very hot spot. This divider also hurts flow by taking up space in the port. The FR500 head has a thin dry divider and better flow as a result.
The bottom line....keep your 5.4 navi heads. The bigger intake port is a plus and the better cooling in the exh port is a big deal on a boosted engine...As they both have 37/30mm valves, That becomes the limit just as much as the other factors.....Al

Further.. I have a '03 cobra engine here. It is still assembled so i haven't had a close look but... The intake port is the same size as a '99-'01 cobra and about the same shape as a FR500 intake port. The exhaust is a rectangle and quite a bit bigger than any of the production heads including the FR500.
 

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Boss 330 keep us posted on the 03 heads. I am sorry for not keeping up with the HUGE forum on the corral. i am simply intimidated by the 667 posts that i would have to sort through. tell me you have catalogued the info somewhere. :( just curious though what is the going rate on a set of navigator heads.

Boss 330 could you pm me with the cost on your intake for these heads. already have a hci intake if that makes a difference. i am curious if i upgraded how much either choice would cost.
 

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I looked into this for my project, and after many coversations with builders (including Boss), I will be sticking with my Navi heads.
 

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I do have to say the exhaust side of the Navi heads need work. Here is a PIC of a race ported exhaust port on a 01 Navi head. This guy goes by JR - who was building this engine, so questions on this head can be asked via his e mail ([email protected]) . As you can see they have potential. - John
 

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I have seen all year heads make exceptional power. Until one person runs both heads on the same combo in different applications, I will be skeptical. People I have talk to rate them in this order from worst to best. 96-98 swirl port, 99-01 tumble port, Navi heads, then the 03 heads, then the FR500's. All these heads have ton of potential, I would just run what I had.
 

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No one has been able to prove that the FR500 heads are any better than the Navi heads, but the 03 Cobra heads are supposed to have solved the piss poor exhaust ports. I will know soon enough as my set of 03 heads will be here soon.
 

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From what I have seen and from talking to various people, seems as though you can't go wrong with either head when it comes to a power adder combo. Randy Haywood has shown who far one can go with Navi heads and Tim Palmer has gone very far with unported swirl port heads. For n/a applications the tumble port style heads(FR500, 99-01 Cobra, Navi) seem to work a lot better than the swirl port heads. All the big powered n/a cars are all using a tumble port style head. I'm no expert by any means but those are just some of my observations. :)
 

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Someone needs to make pictures of the 03 Cobra heads, FR500, and 01 Navi heads, and compare Intake/exhaust measurements etc. Also flow test them all in stock trim, then dyno them all on the same engine to see real world hp/tq gains/losses. Someone step up to the plate, inquiring minds want to know the best DOHC heads. - John:D

Let's mail MM&F and 5.0 & Superfords Magazine with the above so we can finally stop guessing!
 

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MM&FF... Mod motor experts. In the modular dohc story they said the valve train was arranged so the pushrods didn't interfere with the ports.

Someone needs to make pictures of the 03 Cobra heads, FR500, and 01 Navi heads, and compare Intake/exhaust measurements etc. Also flow test them all in stock trim, then dyno them all on the same engine to see real world hp/tq gains/losses. Someone step up to the plate, inquiring minds want to know the best DOHC heads. - John
There is a real reason why you will most likely never see that happen. The type of testing you propose is extremely expensive. It would require a built engine, specific intake and exhaust manifolds/headers and a superflow engine dyno set up with a fuel system to support a mod motor. Labor costs for a month's worth of time .Etc....
Magazines are fed by advertiser dollars. All the parts mentioned are oem parts. The aftermarket manufacturers have no reason to support it ,I really can't see ford putting up $50-150,000.(they already know how the heads stack up) Their interest seems to be in focus stuff, It's been three years and we still dont have a real FR500 package. Check out the frpp catalog There is almost a whole chapter of focus stuff.
 

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Probably right, but if enough people wanted it, then I think one of them would do it. Look at all the 5.0 heads and intakes, superchargers, etc, that have been tested. Not all those heads and intakes are the same port shape. They just need to stop screwing around and start testing these heads in any way possible to compare them for the readers.

I know it bothers people when the same questions get asked over and over, but I'll probably ask this again later down the road. I hope maybe "later" someone will have gotten flow #'s, or something to compare these heads by. It's irritating to look at all the information and stuff for 5.0's and 5.8's, but we can't get simple answers to questions like the one in this thread.

FYI - I think the exhaust port on those Navi heads I have suck. That's why I'd like to see the other heads compared. If they have comparable intake flow and better exhaust flow, I think I'd buy a different head.

Not flaming - John
 
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