What size?

heavy breather · May 1, 2017

Going to pick up a set of headers for 2003 4.0 V6 with a manual trans. I have made the mistake of putting to much exhaust on a truck before and lost quite a bit of bottom end, I don't want to do that again. So what size seems to be the best for the 4.0?

Along with headers, I will probably do new cats and muffler. Speaking of that, I listened to a bunch of youtube videos last Saturday and most of the aftermarket mufflers made the truck sound horrible, like they were little 4 banger Hondas. I think the best one was a Flow Master 40 or 44 series, I don't remember for sure. Any thoughts or input?

heavy breather · May 1, 2017

And has any one had good luck with the magnaflow universals? I put a set on a big block suburban and they worked great, but not sure how Fords would tolerate an aftermarket cat.

RonD · May 1, 2017

Exhaust manifolds/headers are "tuned" to Scavenge power from exhaust pressure/velocity

These "tunes" create a lower pressure at exhaust valves that help pull exhaust out which leaves more power on the crank because it doesn't have to push as hard to get exhaust out.
Tuned exhaust comes in 3 types, low-RPM, mid-RPM and high-RPM
The lowest pressure at the exhaust valves happens in low, mid or high RPM range
Stock Ranger exhaust is mid-RPM tune

Most popular for street driving is low-RPM
Racers of course get high-RPM tune

The tuned part is the diameter of the pipe(velocity) and the length of the pipe(RPM range) from head to Collector(where these pipes meet).

No 4-stroke engine runs better with Back Pressure, popular Myth
The Myth comes from people sticking on larger diameter pipes at the head, "free flow exhaust", and then finding out they lost power, " WTF!, engine must need back pressure"
What happened is that they lost the scavenged power from the stock exhaust, no back pressure involved.
Try sticking a potato up the tail pipe and you will find out how well engine runs with back pressure, lol.

So you need to decide what range you want best power in, low, mid, or high and then get the headers that were designed for your engine and that RPM band.

After the collector you can go as large as you want as far as diameter, larger pipes usually get a lower tone which many like.

On dual exhaust there is a secondary scavenging that can be used, "H" pipe or "X" pipe, between the separate exhaust pipes, not a big change but not 0 either, just hard to implement on some vehicles

heavy breather · May 1, 2017

So what is the relation of the size of the pipe and length to the RPM range? I would guess that shorter smaller diameter would give better performance in low RPM range where large diameter and longer would give better top end performance. But I would only guess that based on my previous assumption that you said was false.

I guess I will be checking out my google function later today any way, but from my perspective as a descent parts changer, you seem to have quite a bit of knowledge and I appreciate your input.

RonD · May 1, 2017

Header design is above my pay grade, lol.

There are some good articles out there on it, I think -3 to -5 psi is pretty good, some NASCAR designs are up to -7psi, or down to, lol.

It basically works like this:
When you have a 1" pipe with a velocity of air flow and it dumps into a 2" pipe there is a pressure drop in the 2" pipe, like a siphon effect.
Now if 2 other 1" pipes(V6 bank) are also connected to that 2" pipe then they will have that same pressure drop, as the high velocity air comes in on one of the other pipes on that collector

The actual size of the 1" pipe is determined by what velocity you want in that pipe which would be based on engine cylinder size, exhaust valve and port size, you want high velocity but no back pressure, so fine line there
Then the ratio of that size pipe to the 2" collector pipe will matter to set collector pipe size.
The exhaust velocity "Pulses" changes with RPMs, so the time it takes a "pulse" to reach collector also matters

Anyway, above my pay grade,

heavy breather · May 1, 2017

ya, well above mine as well, like I said, I am a good parts changer, not so good at diagnostics and other aspects of auto repair and building. That's why I sell parts, not fix them.

heavy breather · May 1, 2017

Summit puts out some tech videos. According to their guy, to find your primary tube diameter you follow this formula. Peak torque RPM times the displacement of one cylinder ( in my case 4.0L V6 = 244 CI. 244/6=40.6 so I just used 40.) divided my 88,200= primary pipe size.

so in may case, the closest I can come to a common production sized primary tube is 1 5/8, it should be closer to 1 1/4, but I don't know of any one who makes a 1 1/4 primary tube header. This is all assuming that the peak torque is around 2500-3000 rpm

The video also explained the short headers allowed peak torque at lower RPMs, than Longer headers.

heavy breather · May 1, 2017

So You Tube is full of videos on headers and mufflers and what not. But the issue that I am running into, is that most of the videos are showing high RPM applications where air flow is a huge issue, I am talking the above four thousand RPM applications, like street strip cars. I have yet to find anything for 4x4 and small displacement applications.

RonD · May 1, 2017

JBA sells 4.0l OHC(SOHC) headers for Ranger/Explorer use, they would be made for lower RPM range
Seen here: http://www.jbaheaders.com/feature_pages/04rangernew.asp

Mustang 4.0l SOHC headers would be mid to high range

Never used JBA so not an endorsement, just found the site

heavy breather · May 1, 2017

RonD said:
JBA sells 4.0l OHC(SOHC) headers for Ranger/Explorer use, they would be made for lower RPM range
Seen here: http://www.jbaheaders.com/feature_pages/04rangernew.asp

Mustang 4.0l SOHC headers would be mid to high range

Never used JBA so not an endorsement, just found the site

I am going to order the JBA headers on your recommendation, then when I am not happy with them, I will complain on here about it :icon_confused:

heavy breather · May 1, 2017

Summit has the JBA headers for $420.00 Amazon has a off brand for $168.00, guess witch ones this cheap bastard is going to try? That"s right, the cheap ones. I figure with Amazon's return policy I won't really loose any thing except some time and labor.

The off brand ones look very similar, but without being able to compare them side to side, its hard to say just how different they are.

RonD · May 1, 2017

Not unusual for a company to "do the math", i.e. spend money on R&D, and then have another company buy a set, disassemble it and copy it.

Most "knock offs" are just that

You gamble is that "the other company" has higher copying skills than their Moral standards

heavy breather · May 2, 2017

I agree 100%, it is a gamble, but like I said I am only out time and my own labor.

swynx · May 2, 2017

everyone i know of seems very happy with an aero 2525, flowmaster sound without that annoying drone.

What size?

New Member

New Member

Official TRS AI

New Member

Official TRS AI

New Member

New Member

New Member

Official TRS AI

New Member

New Member

Official TRS AI

New Member

Active Member

Sponsored Ad

Sponsored Ad

Member & Vendor Upgrades

Truck of The Month

Recently Featured

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals