Head Questions Answered!!!

[Shifty]

For all my brothers that have ever questioned or wondered about Cobra Heads:

Note: This info comes from one of the most knowledgeable and respected guys on cobra heads - NASVT (he is a H/I god)

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Ported 99/01 heads are far better than stock 03/04 heads.

Stock 99/01 heads would be better than ported 96-98 heads.

Ported 03/04 heads would be the best (except for the FR500s)

Porting is the great equalizer and can make most any head better than the next, well, except for making a 96-98 head better than the 99/01s or the 03/04s. The newer heads will always be better than the 96-98s.

Also, the newer heads use a much better intake manifold. The 96-98 intake is not a good design and I can't think of an rpm range or use for which it's suited.

If you are changing heads, go with the either of the newer heads. I personally would go for ported 99/01s because they are available and much cheaper than the 03/04s.

As for that B-head stg 3 port job providing 45hp gains, that's BS. Maybe a port job combined with aggressive cams. That goes for the stg 2 port also, another BS. If the engine is n/a and they should not make the ports bigger, tehy are already too big. Enlarging the ports will reduce low rpm power and put the peak power rpm out of reach for any stock shortblock. The port should only be reshaped and the bowl areas cleaned up, especially on an engine that is not going to see over 7K. Definitely no gasket matching as this will increase port volume significantly.

Now, if you do have ports that are enlarged greatly, you have to run cams that can use that port volume efficiently. The cams would have a lot of duration and a narrow lobe center which would result in a lot of overlap. Not what you want for the street. This would require at least a 4.56 gear because you would have no power below 5k. JimsSVT's car has heads that have been polished and cleaned up only. His cams are aggressive but don't ahve too much overlap and he makes 380rwhp. This proves you don't have to go crazy with the porting on B-heads.

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The problem with that "oh so sexy" intake is that it stinks. The design is just awful and in no way do the inner workings of it resemble a power producing intake.

I stayed with my B heads because I'm a cheap bastard. I learned from that but have since found a way to make them work in a "not so bad" way on my n/a motor. It's compromise that doesn't have to be made with the C or 03/04 heads but nevertheless, its still a compromise and cost me more in the long run. Still got me over 350rwhp with unported B heads though.

Sticking with B heads will be a compromise on an FI engine also. You will still not have the low end provided by the newer heads nor will you have the increased power provided by the newer heads. The Bs will be closer up top but at the low end will be much lower. Now, if the supercharger of choice is a positive displacement blower then the shortfall of the B heads could be overcome by the added boost in the low rpm range, but then again, none of the positive displacement blowers for the B heads have an intercoooler so boost would be limited due to intake charge temps.

So, with the vortech and B heads expect a soggy bottom end like you have now and that cannot be overcome by adding more gear because you ahve a supercharger.

With newer heads and the vortech you can expect more power at the low end and also the upper rpm range.

It all comes down to money you have to spend, how much power you want and where you want the power to be.

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'B' Heads:

http://img94.imageshack.us/img94/9599/tabresbowls1.jpg

'C' Heads: MISSING!

03/04 Heads:

http://img682.imageshack.us/img682/495/03headbowl.th.jpg

http://img682.imageshack.us/img682/6229/03cobraport.th.jpg

Notice the difference in the port shape between B heads and 03/04 heads(or C heads). Two distinct ports(Square Port gets covered by the IMRC until 3250 RPMs) versus one large oval that splits into two. Another downside to the B heads is revealed here, they get dirtier in the Square port faster than the Round, due to the fuel injector only "washing" the round port. Gunking of the IMRCs is a common problem as well. So switching to a later head or simply making IMRC deletes will reduce maintenence as well(but you lose much needed torque, to optimize these heads the IMRCs should actually open closer to 4000rpm).

^^^No way another noob should EVER ask if a damn M112(03/04 Eaton Supercharger) will fit on 96-98 cobra.

Edited July 17, 2012 by Shifty

[Shifty]

Mach 1, 03/04 Cobra, Aviator, Marauder, Navigator

Intake: 184 deg @ .050/.397" lift (measured duration)Exhaust: 196 deg @ .050/.397" lift

114 LCs

The lincoln intake cams I checked have 184 deg duration also.

96-98 Cobra

intake PN#s F6ZE-6A270-AB crosses to F6ZZ-6250-AA

F6ZE-6A271-AB crosses to F6ZZ-6250-BA

Intake: 202-204 deg @.050/ .397 lift (measured durations varied between cams with the same part number and the primary and secondary lobes have the same durations and LCs)

Exhaust: 196 deg @.050/.397 lift

114/114 LCs

99/01 Cobra

Intake: 200 deg @.050/.397 lift (measured duration)

Exhaust: 196 deg @.050/.397 lift

114 LCs

FR500 (M-6550-T46)

intake: 212 deg @.050 /.472 lift (measured duration)

exhaust: 208 deg @.050 /.472 lift (measured duration)

109 LCs

GT Cams: (actual as tested numbers, not Ford specs)

Intake: 189 @ .050"/.424 lift (measured duration)

Exhaust: 190 @ .050"/.448" lift (measured duration)

The centerline is up for debate as this set tested at 122/118 but I think Ford states the LCs as 114/114

Cobra R cams:

Intake: .515'' lift 212 deg dur @.050

Exhaust: .468'' lift 212 deg dur @.050

B/Swirl Port: (93-97 Lincoln Mark VIII, pre 99 Lincoln Continental, 96-98 Cobra).

The only production Ford head with two (square primary, round secondary) intake ports per cylinder, these swirl port castings arrived first in the ’93 Lincoln Mark VIII. Aptly named, due to the way they promoted the incoming air to swirl into the combustion chambers. full sink.

Through the years these heads have proven themselves to be excellent performers for power adder applications--since their tremendous combined intake port cross sectional area and volume (when combined, a full 55cc more than any other 4.6L head design) provide for exceptional power production in the upper regions of the tach. Ironically, it’s those same big, beautiful, twin ports that also prove to be the B head’s largest inherent design flaw. The extra intake port size has a tendency to kill low/mid rpm intake port velocity and power production—hence the use of Ford’s first IMRC (intake manifold runner control) intake on the 96-98 Cobra. By allowing air to reach only one of a B head’s twin intake valves, velocity, and therefore low/mid range torque production was restored in situations under 3250rpm. Later head designs are clearly superior in this regard, which happens to be the one of the most important considerations for those wanting a stout street motor.

There is also some controversy over the single fuel injector/dual intake port setup. Some claim insufficient air/fuel mixing because of the compromised design, however, others contest that the ability to make 1000+rwhp with only minor porting and some form of power adder is testament to the contrary. Whoever you believe, there is little doubt that even after as little as 8,000 miles, carbon and other deposits tend to form on the secondary ports, causing a major airflow impedance, as there is no fuel present to clean them. B heads feature a somewhat small stock exhaust port that really hinders flow in power adder applications. Major gains from porting come with a quality valve job, some pocket and lots of exhaust work. There really isn’t a lot of material to remove from the intake ports themselves.

The Bottom Line: B heads aren’t the best choice for a naturally aspirated street motor. In order to really shine, they need to be paired with a power adder and a short block that can sustain high horsepower and rpm levels. These, the oldest heads, may still be a great choice for full race applications.

Stock Intake Choices: ‘93-‘97 Lincoln Mark VIII, ‘96-‘98 Cobra.

Aftermarket/Modified Stock Intake Choices: short runner

B head dimensions: Combustion Chamber: 52cc, Intake Port Vol.: 107cc primary (square), 115cc secondary (round). Intake Port Entrance: 1.500x1.300” primary (square), 1.660x1.400” secondary (round), Valves: 37mm Int., 30mm Exh.

C/Tumble Port: (99/01 Cobra, 99 Lincoln Continental).

These second-generation Ford DOHC heads feature a single intake port per cylinder with a smaller cross sectional area that boosts incoming airflow velocity compared to previous years. To understand how C heads earn their “tumble port” designation, try to imagine an Olympic high diver doing repetitive front somersaults before cleanly entering a pool at the bottom. This controlled tumble allows for better air/fuel mixing than in the earlier swirl port heads. The new port design allowed for both substantial increases in midrange torque, and superior horsepower production under 8000rpm when compared with earlier heads. Combustion chamber size is also up 2cc.

The design downfall of C heads, and their larger (5.4L Navigator) cousins, is the relatively flat floor and utter lack of a short turn radius in the throat of the intake port. As such, the incoming air tends to overshoot the valves, making the port think the valves are smaller than they actually are. Some ‘99/’01 Cobra owners reported a “ticking/pinging” noise coming from the drivers side head of their cars. This is due to insufficient cooling around the #6, 7, and 8 cylinders that allowed the valves to overheat and therefore seat improperly. Ford remedied the situation by issuing a TSB to remove and replace the affected heads with a version that featured altered coolant flow.

C heads feature a small exhaust port much like Ford’s earlier swirl port heads, but unlike in B heads, both the intake (throat region) and exhaust ports can see extensive porting work. However, removing too much material from the intake port (mouth region) of a tumble port head will kill velocity very quickly, so make sure your head porter knows what they are doing!

The Bottom Line: C heads remain a viable performance upgrade for those looking for more punch in their street driven 4.6L four valve, without having to pay new part prices for the ’03 DOHC or FR500 versions. The increased midrange torque production and greater overall area under the power curve (when compared to swirl port heads) will enhance the performance of a street/strip driven (8,000rpm and under) modular regardless of application.

Stock Intake Choices: ‘99/’01 Cobra, ‘03/’04 Mach 1 & Aviator, ’03 Marauder, FR500.

Aftermarket /Modified Stock Intake Choices: short runner/ported ‘99/’01 Cobra, Sullivan intake, FR500, Aviator

C head dimensions: Combustion Chamber: 54cc, Intake Port Vol.: 177cc, Intake Port Entrance: 1.960”x1.350”, Valves: 37mm Int., 30mm Exh.

Navigator: (98+ Lincoln Navigator)

These 5.4L DOHC heads feature essentially the same intake port design as C heads, however they have a much larger intake port volume than 4.6L castings. Despite the fact these heads feature a relatively small exhaust port, the extra intake port volume could be very beneficial in helping fill a motor of greater displacement—think 5.4L. Expect slightly better midrange torque, and sub 8000rpm horsepower production than even C heads, however the larger intake port size leaves a slim selection of intakes to choose from when utilized on a 4.6L block. Forced induction fans take note, Navigator exhaust ports feature a thicker exhaust divider (while keeping the same overall exhaust port size as B,C, and FR500 heads) that allows coolant to circulate through this vital area. Conversely however, the larger divider can also hurt flow by utilizing additional space in the port.

The real downside to Navigator heads, when used on a 4.6L based motor, is the severe limitation they impose on intake selection. The physically larger 5.4L heads don’t leave a lot of room (when installed on a 4.6L block) between them for an intake plenum to sit—though they do bolt right up. Remember that since Navigator intake ports are essentially clones of those of C heads (just on a larger scale), they too suffer from the same intake port flaws that plague the earlier tumble port design--no short turn or floor in the throat of the intake port.

The Bottom Line: The extra port volume the Navi’s possess could be very beneficial in filling a motor with greater than 281 cubic inches of displacement, or in high rpm N/A street/strip or boosted combinations. Fans of boost should remember the cooled exhaust port divider. Lack of intake availability is the real downfall of this otherwise wonderful casting.

Stock Intake Choices: None (4.6L), 98+ Navigator (5.4L)

Aftermarket/Modified Stock Intake Choices: short runner 99 Cobra (4.6L), sheet metal

Navigator head dimensions: Combustion Chamber: 53cc, Intake Port Vol.: 184cc, Intake Port Entrance: 2.290”x1.400”, Valves: 37mm Int., 30mm Exh.

’00 Cobra R: (’00 Cobra R)

Cobra R heads are bar none the best Modular heads available today. However, their extremely scare supply makes them both ridiculously hard to find, and unbelievably expensive.

Initial performance results are understandably hard to obtain, however Al Papitto reports that with only 25hrs of port work into the his new ‘00R heads, they have already eclipsed the performance of his old Navigator heads with months of labor in them. These heads feature larger intake and exhaust ports, +1mm larger exhaust valves, and a dry exhaust port divider. Cobra R heads also require the use of a specific valvetrain not shared with any other modular application due mainly to their overall physically larger size. Al also claims R heads have too much port volume for a street/strip 4.6L application; only consider them with a larger 5.4L motor or a serious 4.6L race application paired with some form of power adder.

The Bottom Line: The best heads you can or can’t find for a Modular four valve motor.

You are as likely to come across a set of these Modular “Godfather” heads as you are to be Brittany Spears’ next uterus masseuse. Though based on their performance abilities, you may want to start saving, just in case…

Stock Intake Choices: None (4.6L), ’00 Cobra R (5.4L)

Aftermarket/Modified Stock Intake Choices: Sheet metal

’00 Cobra R head dimensions: Combustion Chamber: N/A , Intake Port Vol.: N/A , Intake Port Entrance: 2.370”x1.300”, Valves: 37mm Int. 31mm Exh.

Stock Intake Choices: ‘00R

Aftermarket Intake Choices: Sheetmetal.

FR500: (FRPP)

The sole “aftermarket” offering of the bunch, these high flow heads feature a modified C head intake port combined with the smallest port volume of the group—it seems Ford meant to design these heads for high performance naturally aspirated applications. With the same small standard exhaust port as most other DOHC heads you will still have to remove a decent amount of material from the exhaust ports. Port entrance shape/size remains identical to C heads so finding an intake isn’t hard. These heads are capable of producing power beyond 8000rpm, where earlier versions of the tumble port castings begin to lose their luster. FR500 heads are prone to the #6,7, and 8 cylinder cooling problems as well. Major intake port differences between these and earlier tumble port heads include a raised intake port roof, and a real short turn radius that better directs the incoming air into the combustion chamber; not over the valves like in earlier versions of tumble port heads. These heads also feature a dry divider in the exhaust port, which allows for greater flow, but also higher temperatures. Though improved, the heads can still use some TLC from a quality porter to smooth the roughly finished and newly implemented short turn radius, and the standard exhaust treatment.

The Bottom Line: Outstanding performance heads, with exceptional low and mid lift flow capability. The FR500s only real fault is that the newer ’03 DOHC heads provide near identical performance capability (much better on the exhaust side) paired with a cost differential that is approximately two-thirds less than the FRPP castings. Still a great choice for any application, the heads readily pair to a wide variety of stock and aftermarket intakes.

Stock Intake Choices: ‘99/’01 Cobra, ‘03/’04 Mach 1 & Aviator, ’03 Marauder, FR500.

Aftermarket /Modified Stock Intake Choices: Al Papitto short runner/ported ‘99/’01 Cobra, MP/Sullivan carb intake, FR500, Aviator.

FR500 head dimensions: Combustion Chamber: 53cc, Intake Port Vol.: 160cc, Intake Port Entrance: 1.960”x1.350”, Valves: 37mm Int., 30mm Exh.

‘03 DOHC head: (‘03+ Aviator, Marauder, Cobra, Mach 1, Australian Boss 260/290)

Featuring a nearly identical (though 17cc larger in volume due to the fact that they are also used on the much larger Australian Boss 260/290 5.4L DOHCs) intake port to the FR500 head, but combining it with a newly designed, larger and more rectangular exhaust port, these may be the best all around DOHC Ford heads ever manufactured. The improvements made to the intake port shape over previous years include a raised port roof and the introduction of a short radius turn in the throat of the intake port that helps assure the incoming air charge finds the combustion chamber. For those with a forced induction street/strip motor, these are without question the best heads available, and as with the FR500s, they should produce great power up to and beyond 8000rpm regardless of application. ’03 DOHC heads also feature higher quality head castings from the supplier, which is at least partially responsible for the modest increase in flow vs. earlier castings--chalk that up to Ford’s revised quality control standards.

Early runs of the ’03 DOHC head fell victim to the same #6,7,8 cylinder coolant flow problems as earlier tumble port castings. In mid ’03 Ford made a running revision to the ’03 DOHC heads that allowed for more coolant to circulate through the affected areas. A blue mark on the driver’s side head indicates an updated casting, and there are no additional revisions to the ’04 version of this design.

The Bottom Line: On all accounts these are the best modular four valve heads currently available. They combine the exceptional flow of a slightly larger FR500 intake port with a gigantic new rectangular exhaust port.

Stock Intake Choices: ‘99/’01 Cobra, ‘03/’04 Mach 1 & Aviator, ’03 Marauder, FR500.

Aftermarket/Modified Stock Intake Choices: short runner/ported ‘99/’01 Cobra, Sullivan, FR500, Aviator.

’03 DOHC head dimensions: Combustion Chamber: 52cc, Intake Port Vol.: 177cc, Intake Port Entrance: 1.960”x1.350”, Valves: 37mm Int., 30mm Exh.

In Conclusion

Our panel of experts surmised that aside from the nearly unobtainable ‘00R heads, the ’03 DOHC heads are without question the right choice for your Modular four-valve performance application . The combination of a slightly larger FR500 intake port and modified throat region, coupled with a new larger rectangular exhaust port, and a relatively low price (due to it’s widespread use in the Ford organization) makes the ’03 DOHC casting the current head stud of Ford’s Modular stable.

After porting, the relatively small stock valves/seats become the most serious flow limitation; as such aftermarket replacements should be a serious consideration for those looking to squeeze every last drop of performance from their DOHC heads.

Here are a few basic thoughts on the new 3v heads...

With 34.7mm intake valves and a 38.5mm exhaust valve, on paper the '05 3v heads seem to be an excellent street/strip performance head. The 4.6/5.4L heads are identical with the exception of different valves/springs on the 4.6s that allow them to safely rev to 6200rpm. The VCT (when unleashed by a tune) allows for one hell of a nice torque plateau--especially by comparison to earlier N/A 4v DOHCs.

With that being said, with regard to ultimate power production potential 3v heads are still inferior to 4v castings. Curiously, the intake valves on a 3v head are pushed into the side of the chamber, to the point where a stock valve is unnecessarily shrouded. The location of the seats makes it impossible to install larger seats/valves without actually hurting flow on a N/A motor. You would have thought Ford learned something about unshrouding the valves in a small bore motor during the FR500/Big bore programs. Especially since the limiting factors for flow on all DOHC heads are the valve seats/valves The exhaust needs more help, with its single valve, than the intake as well. Both the intake and exhaust ports appear to be fairly nice, and appear to be (I haven't had a set in my hands to confirm this yet) sporting a higher/raised port than 4.6 4v heads. I haven't heard anything about short turn casting quality yet either.

I'm still waiting for the VCT 4v motors

[Shifty]

Probably another 3 posts coming to add onto this one.. time for lunch lol

[Mystic SVT]

Actually, the C head intake (99-01 cobra/mach) is the choke point to the C heads, the B head intake is actually better suited for higher RPM than the C head intake, Todd (na-svt) is the one who said this. He's the one who built my shortrunner intake. If the B head intake could be bolted up to C heads it would provide better numbers than the C head intake.

[Shifty]

Um... what you are reading.. was in fact posted by Todd himself.. If you read the top part I say that. So unless he changed his info. Maybe Ill contact him then and see.

So basically every single person out there that uses the 99/01 intake is just because there isnt another intake out there that bolts up to the C heads? Have never heard that or anything good being said about the stock 96-98 intake. But again. I guess I could be wrong

Edited July 17, 2012 by Shifty

[Mystic SVT]

Well there is a better intake other than the stock mach/cobra intake, the FR500. Todd is actually working on an adapter to be able to bolt up the 96-98 cobra intake to C heads. He said the 96-98 cobra intake has better high rpm potential than the stock cobra/mach intake and its also easier to work on and make shortrunners out of. The C head intake takes a lot more work to shorten the runners compared to 96-98 intakes.

[AZSN95SNAKE]

Actually what mystic posted is on SVTp in the sn95 cobra section right now. Me though I have no facts but I would believe the B head intake is better for high RPMs since it was made for high rpm B heads.

[DOHC GT]

Well there is a better intake other than the stock mach/cobra intake, the FR500. Todd is actually working on an adapter to be able to bolt up the 96-98 cobra intake to C heads. He said the 96-98 cobra intake has better high rpm potential than the stock cobra/mach intake and its also easier to work on and make shortrunners out of. The C head intake takes a lot more work to shorten the runners compared to 96-98 intakes.

i thought the adapter was for the 96-98 intake lid to bolt to c head intake....mostly an aesthetic mod?

[Shifty]

Aight mystic.. you were right.

The FR500 intake is best for power abover 6000rpm but produces terrible mid range hp and tq.

The C head intake is good for mid range hp and tq, after 6300 it falls off quickly. It's only the best for making power in those areas, nothing else. n/a or FI the B head intake kicks it ass in making power above 6000

He is also looking into taking the short runners and putting them with mark8 adapters.

Interesting stuff

[Mystic SVT]

i thought the adapter was for the 96-98 intake lid to bolt to c head intake....mostly an aesthetic mod?

He made an adapter for the B intake lid to bolt on to the c head lower, but he just needed someone with a waterjet to cut it out. He's working on using '99+ continental Intake adapters to hopefully be able to bolt up the B head intake to a C head motor. This would be the best of both worlds.

[Mystic SVT]

The FR500 makes terrible torque down low if the variable runner control is removed. It uses a shortrunner/ longrunner setup, longrunner for lowend grunt and shortrunner for high rpm's.

[massacre]

I have a set of the '99-'01 Lincoln Continental plates that will mate a B-head intake to C-heads.

[Mystic SVT]

I have a set of the '99-'01 Lincoln Continental plates that will mate a B-head intake to C-heads.

Those plates only work for the lincoln intakes not the cobra intakes. Would you like to sell them?

[DOHC GT]

He made an adapter for the B intake lid to bolt on to the c head lower, but he just needed someone with a waterjet to cut it out. He's working on using '99+ continental Intake adapters to hopefully be able to bolt up the B head intake to a C head motor. This would be the best of both worlds.

that would be sick!! i already have a b head shortrunner from him, and i want to step up to c heads but keep my shortrunner.

[330CubeGt]

Anyone know if NASVT buys 96-98 Intakes? I have one here i purchase to make a short runner and its all apart with runners already cut down but it needs to be ported and put back together

[Mystic SVT]

^^^Why not just put it back together and have yourself a shortrunner intake? No real need to port the intake, just clean up the intake floor and runners (closest to head). You don't happen to have an extra intake lid do you?

[330CubeGt]

Currently i just have one extra intake, Hat to IMRC's.. But would not be willing to split up Idk that i would make enough on the lid to consider selling it...

My buddy funded the intake to make a short runner to sell to make a few bucks but with never doing it. We managed to put a small hole in one of the runners. Its an easy fix with epoxy but might try to weld it up. Either way i might just put the half assed short runner project on my car and sell my stock intake and IMRC deletes to pay him back as i think it will be hard to sell a project intake...

[WildWillyWalker]

'Favorited'

If you really want to learn about mod motors buy "How to build max-performance 4.6-liter Ford Engines." SA82. I saw it on pepboys.com for $10 and picked it up at a local pep boys. I then bought "How to rebuild 4.6-/5.4-liter Ford Engines." SA155P. I got that one from work. My friend got them too since he bought a complete 98 cobra motor but it had a cracked block so then he bought another block and heads. Plus, I bought a 99 cobra short block. His shed looks tits now.

[massacre]

If you are referring to the SHM book, it is a good introduction into the Modulars but there are definitely mistakes in that book.

As far as the Conti plates, I am not looking to sell at this time.

There are guys doing 5.4DOHC longblocks with Coyote and Boss intake manifolds.

Some fabrication is involved.

[scottydsntknow]

What aboot ported PI heads vs some of the 4V offerings? Seeing plenty of 2V cars in the 500-700whp range on not that crazily ported PI heads, aftermarket cams and 20+ psi. Also where could one get a set of 99-01 C heads ported/gone through to make them a better investment than 03/04 heads which I see go for $600 and then probably $200-$300 to have them gone through?

[01yellercobra]

I've heard good things about Fox Lake. That's who I'd like to use if I ever get around to having a set of heads ported.

Misspelling brought to you by Tapatalk

[scottydsntknow]

MHS is doing 4V heads again too. In any case, stay the hell away from Patriot.

But just doing some research... getting the 99/01 heads ported you are going to be into it for as much or more as a gone through set of 03/04s and I can't see the gains being all that great. Stage 2 PI heads are $1500 with brand new castings and everything, used cams are everywhere and make great power and all the 4V options are available for the 2V. Turbo, Eaton, KB, Centri, whatever.

[01yellercobra]

MHS is doing 4V heads again too. In any case, stay the hell away from Patriot.

But just doing some research... getting the 99/01 heads ported you are going to be into it for as much or more as a gone through set of 03/04s and I can't see the gains being all that great. Stage 2 PI heads are $1500 with brand new castings and everything, used cams are everywhere and make great power and all the 4V options are available for the 2V. Turbo, Eaton, KB, Centri, whatever.

Are you trying to compare doing a 4V swap to staying 2V? It's possible to get a 2V head to flow. But I think you're going to have to go with something like a ported Trickflow head to get 4V numbers.

If I had a choice, I would go 4V. But that's just me. I've seen what fully ported PI heads can do. But it took a lot to get them there. Even compared to stock 4V heads.

Misspelling brought to you by Tapatalk

[scottydsntknow]

No I'm not trying to compare flow numbers, the 4Vs do FLOW better (even the TF heads won't flow like 03/04s especially on the exhaust side) but flow is not everything and when you start cramming boost into the motor it equalizes things out a LOT. If you want a 10 second street car, there is no need to go to 4V but I've seen Continental C heads go for $200 cash picked up. Another $200-$300 to go through them and you have a $500 set of really nice heads even if they are inferior to the 03-05 units. Ported PI heads to get you into the 500-700whp range are going to run $1600 minimum which is one reason threads like this really interest me when it comes to the C heads. It seems like the Revised heads command a pretty good premium but honestly how much better are they vs the 99-01 C heads when one is talking about cramming 15+ psi of boost down their throats? I know the lack of a short turn radius can cause the air to overshoot the valves but again... boost is the great equalizer.