B Heads

[massacre]

This thread is being presented as a factual, technical discussion. This is not the place for snide comments please. It's OK to disagree but it doesn't have to get nasty. If it does I will ask that the thread be deleted immediately.

Many do not know the finer points of the B heads, many think they are just older but just as good as the C heads. This is not the case at all and I will show you why.

One of the biggest problems with the B heads, besides having intake ports that are too large to create the proper intake velocity for performance in an engine that is only 271 cubic inches, is fuel injector placement.

The B heads have 2 intake ports per cylinder. The fuel injectors are placed above the primary intake valves. The secondary intake valves are blocked off from airflow by a butterfly until ~3500rpm when they are opened, either by a vacuum solenoid (early) or an electric motor/cables(later). Both methods are controlled by the ECM.
Because the secondary intake valve doesn't get sprayed with air/fuel mixture, it gets really gunked up. How gunked up?
Check this out:
http://imagizer.imageshack.us/v2/640x480q90/856/img1210f.jpghttp://imagizer.imageshack.us/v2/640x480q90/35/img1207o.jpg
http://imagizer.imageshack.us/v2/640x480q90/835/img1208iv.jpghttp://imagizer.imageshack.us/v2/640x480q90/571/img1209q.jpghttp://imagizer.imageshack.us/v2/640x480q90/96/img1207jv.jpghttp://imagizer.imageshack.us/v2/640x480q90/715/img1209mw.jpg

All of these valves were removed by me from a running and driving Mark VIII. I have more pics but they all look exactly like this. In each picture, the primary intake valve (that gets sprayed with fuel) is on the right, and the secondary intake valve (that does not get sprayed with fuel) is on the left.
We can agree that that much carbon and crap on the secondary valves certainly is hurting performance and can eventually clog completely, creating bigger problems.

Let's look at the fuel injector placement on a B head intake:
http://imagizer.imageshack.us/v2/640x480q90/923/r1wqp5.jpg
With B heads, the injectors don't mount in the intake, they mount in the IMRC plates. Notice that the primary intake ports (square) have the fuel injector placed next to it, while the secondary ports (round) have nothing.

Now let's look at the C head fuel injector placement:
http://imagizer.imageshack.us/v2/640x480q90/924/pGokgf.jpg

Notice the single, oval ports with injector placed right in the center, allowing both intake valves to receive fuel spray. And those of us who have dismantled these heads know, there are no known issues with 1 valve looking new and 1 valve looking like crap in these engines. Both intake valves will look the same.

There have been people who tried to actually move the B head injector placement to make it more desirable but IIRC it ended up getting really technical and really expensive and was abandoned. I just spent an hour looking for the website that the guy had started but could not find it.
There have also been crazy intake designs, pretty cool designs but no one would raise the money to build it. Again, tried to find the website but was unable to.

So basically these are a few design flaws that make the B head more trouble than it is worth IMHO, seems like all the people who pursued solutions ran out of money and gave up.
Also keep in mind that deleting the IMRC butterflies does not change the injector placement. To be honest I think the solution from Ford should have been 16 fuel injectors, 1 in each intake port, it's hard to spray 2 intake ports with only 1 injector.
Thanks for reading, I will post more as i have time.

[mm svt]

MMR has the plates to delete the butterfly's, they look nice and probably work well. Where are the photos of the actual B heads? This is one discussion that's been beat to death on the mustang forums.

https://www.svtperformance.com/forums/threads/98-cobra-b-heads-or-c-heads.874962/

B heads: Intake: 230 cfm at .500" of lift
Exhaust: 145 cfm at .500'' of lift

C heads: Intake: 225 cfm at .500" of lift
Exhaust: 145 cfm at .500’’ of lift.

03/04 heads: Intake: 233 cfm at .500" of lift
Exhaust: 168 cfm at .500 of lift

3Valve heads: Intake 223.2 cfm @ .500" lift
Exhaust: 148.2 cfm @ .500" lift

[mm svt]

Sean hyland had this figured out when the b heads were all they had

https://www.seanhylandmotorsport.com/parts-accesories/1996-2004-mustang/cylinder-heads-cams6

[Joe Walsh]

I'm a little confused...

Why would anyone waste so much time, effort and money trying to make 'B' heads work when you could just use 'C' heads?

My SBF analogy would be someone spending a bunch of time and money trying to make cast iron 351W heads perform on their 5.0
when there is now a lot of better options available....:dunno:

[massacre]

MMR has the plates to delete the butterfly's, they look nice and probably work well. Where are the photos of the actual B heads? This is one discussion that's been beat to death on the mustang forums.

https://www.svtperformance.com/forums/threads/98-cobra-b-heads-or-c-heads.874962/

B heads: Intake: 230 cfm at .500" of lift
Exhaust: 145 cfm at .500'' of lift

C heads: Intake: 225 cfm at .500" of lift
Exhaust: 145 cfm at .500’’ of lift.

03/04 heads: Intake: 233 cfm at .500" of lift
Exhaust: 168 cfm at .500 of lift

3Valve heads: Intake 223.2 cfm @ .500" lift
Exhaust: 148.2 cfm @ .500" lift


My post was not meant to be a complete and definitive post on the B heads, but to show a couple fundamental design flaws in them which cannot be modified to work correctly. Thanks for posting up the cam specs.

The delete plates don't work to well, since the intake runners are TOO LARGE to generate the needed intake velocity in a 281 cubic inch engine. The delete plates do nothing to aleviate this issue.

As far as pictures of the B heads, i can post some up if necessary. Your SHM link didn't take me anywhere specific.

[massacre]

I'm a little confused...

Why would anyone waste so much time, effort and money trying to make 'B' heads work when you could just use 'C' heads?

My SBF analogy would be someone spending a bunch of time and money trying to make cast iron 351W heads perform on their 5.0
when there is now a lot of better options available....:dunno:

My guess is probably getting them for dirt cheap, not realizing that there is a reason why they are so cheap.
C heads cost more initially but save money in the long run.

[ByronRACE]

I have not yet seen an explanation as to why the seemingly similar flow numbers behave so dramatically different in forced induction applications.
Anyone that has dyno'd a 10psi B headed engine vs a 10psi 03/04 headed engine with the same supercharger and ratio, etc... has experienced gains that seem to be bigger than the flow bench numbers. They must behave dynamically different in other ways as well. I was very surprised by how well the factory 03 head design compared, even to ported previous design heads. It's more than just the flow bench numbers for sure; but what.


MMR has the plates to delete the butterfly's, they look nice and probably work well. Where are the photos of the actual B heads? This is one discussion that's been beat to death on the mustang forums.

https://www.svtperformance.com/forums/threads/98-cobra-b-heads-or-c-heads.874962/

B heads: Intake: 230 cfm at .500" of lift
Exhaust: 145 cfm at .500'' of lift

C heads: Intake: 225 cfm at .500" of lift
Exhaust: 145 cfm at .500’’ of lift.

03/04 heads: Intake: 233 cfm at .500" of lift
Exhaust: 168 cfm at .500 of lift

3Valve heads: Intake 223.2 cfm @ .500" lift
Exhaust: 148.2 cfm @ .500" lift

[massacre]

I have not yet seen an explanation as to why the seemingly similar flow numbers behave so dramatically different in forced induction applications.
Anyone that has dyno'd a 10psi B headed engine vs a 10psi 03/04 headed engine with the same supercharger and ratio, etc... has experienced gains that seem to be bigger than the flow bench numbers. They must behave dynamically different in other ways as well. I was very surprised by how well the factory 03 head design compared, even to ported previous design heads. It's more than just the flow bench numbers for sure; but what.


Well the B heads are known as "swirl port" heads as Ford was trying to introduce swirl into the combustion chamber. To me, that method worked great on SBF engines in the 80s, as evidenced by Bill Elliot and other Ford racers at the time.
But remember, the 1993 Lincoln MarkVIII was Ford's first production DOHC engine as well as OBD-II had just come out. So it seems to me that they really didn't have a lot of data to go by and just went with something that worked previously.
The C heads are known as "tumble port" heads and they seem to be a much more efficient design for what they are. Seems Ford had enough time to figure out that the swirl port was not the way to go in a DOHC engine, and came up with a better design.

B heads do respond well to boost but there is injector placement to think about. When I think about B head performance I always think of John Mihovetz since he took them farther than anyone. That guy was running like 45lb of boost and pumping a lot of fuel into them so maybe under boost the "swirl port" design really does work as it was designed to, but NA they just don't.
I don't have a definitive answer I have not dynoed identically boosted engines with both head styles back to back.