As fars as the pics Hurst posted.....I wouldnt consider that a port job as much as a gasket match and clean up job. IMO And that will improve any set up when you smooth obstruction out of the flow path

 

Good right up Hurst, but im thinking at least half of your gains from the porting was from shaving the heads the .027

 

So its just the 4.6L DOHC that dont gain from porting, but more from polishing.

 

You could polish it but for the gains Id just leave them be.

 

How much gain from leaving them or polishing them and putting in bigger cams? Is a simple cam swap worth it ? I mean within reason , not so big everything else has to be upgraded.

 

The DOHC gain a lot from porting. Racers have them done all the time.
The thing with the B heads is that the intake ports have so much volume it kills velocity. This makes for great high RPM air flow and HP,.. but kills it for lower RPM grunt. So unless your packing a 88mm turbo for that thing,. I would leave the stock porting alone. At most I would just remov the IMRC plates.

Here are some picks to help me show you the B head compared to the later C heads.

93 - 98 B heads.




And here is 03/04 Mach1 and Terminator heads.




Here are the head data charts. I scanned these from Sean Hyland's book also.





You see on the volume chart where the B heads have 107cc on the primary port and 115cc on the secondary port. Thats a TOTAL of 222cc intake port volume for a little 281ci engine. Thats like taking an AFR 225 head and slapping it on a 5.0. The 302 would need to spin to 7000 to make any HP and have nothing down low. A DOHC B headed motor has similar issues but not as badly matched as AFR225 on a 302. The 96 - 98 Cobra engines have no problem spinning to 7000 RPM (AND BEYOND). And thats why they keep pulling and are making good power all they way to their redline. If your a seat of the pants racer like me (dont really watch the tach) you'll hit the rev limiter every time between shifts on a B headed motor. Its incredible how that motor responds to RPM's.

But on the flip side,.. look at the flow chart. The B heads dont flow any better then the smaller port in the 03/04 Terminator heads. Dont let the chart fool you. DOHC cams dont have a lot of lift. They dont need it to make power. But,.. B heads do flow very well after porting. Turbo guys love B heads because they make gobs of HP at high RPM's and are arguably better at high RPMs then the 03/04 Terminator heads.

Sorry for the hijack AB,.. but you probably found that interesting also.

Hurst

 

The whole reason for the tit area (the NPI tear drop shape as well) was designed that way due to how the injectors spray into the ports. You see those same 'tits' on the DOHC heads for the same reason.

Hurst

 

Possibly some of it,. but also remember,.. I ground out the swirl fins and beveled the edges of the combustion chamber around the intake ports. This opened up the combustion chambers a few CC reducing the compression ratio some compared to how it was stock. The .027cc decking was done mainly to clean up the head surface for better sealing and then to combat any compression I might lose from the combustion chamber porting.

Hurst

 

For a 4V? Guys swap to turbo or S/C cams but also swap to 98 exhaust cams as well. The 96-98 cams seem to flow well for most street applications but if your looking to make hugh hp #s and boost youll be better off swapping them to aftermarket cams. What are you plans for the car?

 

No real set plans , I 've never messed with a mod motor yet and was just to trying to get an idea of what can be done relatively cheap and still get a decent amount of power. Maybe 50 -80 hp over stock. Maybe more , I dont think he wants to go balls out with it. I've never done any OHC type engine