I think anyone is a fool for waisting one minute tryin to port a set of these stock manifolds. How many of you guys have looked at one off the motor? They are HORRIBLE.The only thing that Ford concidered when designing these was fast and easy install at the factory. They are pinched in places that shouldnt be just so the line workers can get a socket and extention on them easy as they go down the line.There is no way to get in them to fix these areas to flow better without cutting them open...and even then it still wouldnt help much.

 

I would buy a set of headers over wasting time on porting some stockers.

 

I want to see some more information on that. All I have ever read is that the ranger cats are high flow from the factory.

I replaced all mine with 2 magnaflow high flow cats, it didnt make that much difference that i can tell.

 

I deleted one of my cats and put in 2.5in tubing in it's place.... Biggesst difference!

 

I don't have any proof for the 4.0L & I've never pulled one apart. I'm speaking in theory only on this one.

As far as reading.. I seldom pay attention to uninformed opinions.
I'll *write* this though.. Why would ford put high flow cats on a vehicle that has a very restrictive cat back system? That doesn't make sense unless they were using the cats from an off the shelf part. (ie.. an already produced car/truck)

Also, the whole point of cats are to superheat and chemically change the exhaust gasses. The lower the delta P across a cat.. the faster it'll move through it. They would have to make the cats longer and run the motor leaner to give the exhaust time to change.


As far as the bumps in the stock manifolds go. There are two things at work. And often times these things have been engineered and tested.
1) Air flow over bumps / dips often times stays laminar. Meaning that it's kind of like an airplane wing. Yes it's obstructive.. but it's also a smooth flow that is not objectionable. A hard step on the otherhand disrupts laminar flow. Picture the leading edge of a wing having a 2" flat face instead of the rounded shape. Keeping flow laminar is critical. Smooth bumps do that.
2) Crossectional area. If there is a bump protruding into the main flow path.. very seldom will they have another bump across from it. If they did it would reduce the crossectional area and choke the flow. I'd be very supprised to see an exhaust manifold (or intake manifold) designed that way from an OEM.


Understanding flow (of any media) within a closed chamber is not always a simple thing to see. It takes an in-depth study of the velocities up/down/around the chamber to say it's "good" or "bad". Basicly.. it just depends on many other things. Things like what's the vectors and velocities of the media entering the chamber? It may not be square to the mounting flange! So.. you can't just look at a bump or shape change and say it's restrictive or not restrictive. It's not that simple.

Headers almost always make more power. But.. you'll **pay** for that extra power. Porting a iron manifold and going with high flow cats is a solid bang for the buck way to gain the loins share of that power. I'm not running down headers... I'm just trying to point out that there are other ways of gaining the majority of the power a header would provide.

Rich

 

at what point tho? WOT? maybe but how often is someone at WOT. In reality.

 

Rich I agree best bang for your buck but only if you have the tools and experience to do that to a cast manifold. I just think for the price or even a set of used headers are the way to go.

 

this is one of the more informative threads, definitely deserves to considered sticky material

 

Definately they give the most power. But at what cost is really a subjective thing IMO. I'd like to add something else to that too.. and that's at what load you use the motor. The higher the load.. the more air you'll flow.

Not just wot or rpms.. but load. Guys who tow, or are at WOT *a lot* would be better suited for headers. But guys who only go WOT occasionally and seldom tow would be better suited spending $200 on some high flow cats and a sat afternoon opening up thier own manifolds.

That's just my *subjective* 2 cents..

Rich

 

For what its worth- I have decided to buy a set of Mac longtubes and attempt to install. if it doesn't work I'll have a like new set I can sell to a mustang owner.

Reailistically it could be 30 days or more before i can report on fitment. I have a tranny swap reversal to do at the same time.

 

I can tell you with 100% certainty that the substrate bricks inside of a Ranger cat is no different than the one used in a Sable,Focus,F150,E150 or TownCar. How do I know? I worked at the Ford/ACH exhaust component plant in Monroe Mi for the last 6 years until they closed it down.I have personaly built complete exhaust systems for all the above mentioned vehicles from the first brick to the cat-back flange. Some are round and some are oval but they are all the same brick other than certain ones got different chemical ingredents depending if they were flex fuel or not.

As far as the ported manifolds go I highly doubt porting will help at all because you cant get to the whole inside of the manifold.Just opening up the first 1" or so of each port will do nothing since the rest of the manifold is untouched and un-reachable.
Also ,unlike a header the stock manifolds on a few cylinders actually share the same runner prior to the collector.

Unless you plan to have a manifold Extrude Honed where an abrasive media is forced thru the manifold removing metal as it travels thru it I think its pointless.

 

have thought of getting several items extrude honed over the years but the price they want keeps me away...extrude hone wants nearly $800 to do a set a v6 iron exhaust manifolds

 

The best bet in most cases is to loosen the manifold bolts and tell the wife the manifold is cracked. the noise from the loose bolts will give the "evidence" needed. I say that as a joke, but I had one on a 3.0 that was cracked. In that case, getting headers was a natural choice.

 

Wayne, could you do a 3rd gear pull data logging TQ before and after?
That would be a nice reality check of what's actually being gained.
It might not be as accurate as a bench test.. but it would be real world and reflective of what a fella would actually gain.

Rich

 

Brian, if they were different in shape and especially in length then they are not the same. Surface area = friction. Friction = a higher delta P. (aka restriction) It really comes down to exhaust velocity vs surface area.
I mean.. even the exact same cat on two different engines will have a greater or lesser restriction on exhaust flow because of velocity.

Example: A short stroke 4.0L V6 will have much less flow at 50% load and 3500rpms than a 3.8L V6 long stroke.

Like I stated earlier.. sharing parts across car platforms is quite common. But that doesn't mean that it'll preform the same. They can tweak things like after cat back pressure, A/F ratio, and even mid pipe shapes/sizes to adjust the velocity entering the cat.


Brian, Respectfully, without me seeing measurement of the heads exhaust crossection and then the manifolds crossection.. I'd not make such a claim.
Again.. I'm not saying they will match the performance of a header. But.. w/o looking at the actual area / volume of the heads port vs the manifold I can't draw a hard and fast conclusion.

Also, on the first 1" thing. Exhaust velocity continually slows from the moment it leaves the exhaust valve. So.. it really depends on what the area / volume is whether or not it'll be worth the work.

Extrude honing is often times more expensive than just buying headers. IMO thats why it would be pointless.

Regards,
Rich

 

i think my head just exploded from all the information put out. i love this site.

 

These are not WHP #'s.

I check every mod on my G-tech and these are before and after the header install.
These are peak #'s on a 3rd gear pull.

Before= 104.7 HP. @4512 RPM 115.5 TQ. @ 4558 RPM.

After=111.2 HP. @4722 RPM 120.6 TQ. @4396 RPM.

Notice how it makes more TQ. down low and more HP. up high.NICE!!


Tony

 

Near impossible to do. My y-pipe has already been hacked to work around a 700r4 tranny. Then hacked up again to remove the tranny as I go back with the stock manual.

This y-pipe issue is why its worth trying to fit the longtubes- I have to deal with a new y-pipe either way.