1967 stance with 1" lowering springs and Arning drop. Header clearance.. 3.5"

[shelbydoug]

Those are tri-y's. Why would you use them?

[2112]

Those are tri-y's. Why would you use them?

Because they don't drag on the ground.

Have you followed NASCAR engine building lately? Sewer pipe exhaust has been largely set aside as that is not where the horsepower is hiding.

This is not to say tiny exhaust works, but 4 huge equal length pipes have marginal gains.

Taking this to the street and it is even more evident.

[1967 eight barrel]

I am running a 2.5" exhaust to the shelby extensions which it is necked down to slip on like factory. I don't see a need to run a 3"+ exhaust like so many do.

[shelbydoug]

Those are tri-y's. Why would you use them?

Because they don't drag on the ground.

Have you followed NASCAR engine building lately? Sewer pipe exhaust has been largely set aside as that is not where the horsepower is hiding.

This is not to say tiny exhaust works, but 4 huge equal length pipes have marginal gains.

Taking this to the street and it is even more evident.

...and a Tesla has a 3.4 zero to sixty. So?

[67GT500#1594]

These were on a forum members car, a custom built set from JBA. Large tube headers that were nearly perfect for my application BUT I have a 4spd and they wouldn't fit. So, it can be done and they can fit without dragging. Even these had a few places but not as bad as Hookers. I had a set of JBA Tri Y's and they were a nice fit as well but not perfect. I've heard good things about the FPA tri y's too. For some of us though, our engines dictate the use of larger pipes. TK go through the expense of building the high end horsepower engines and to strangle it with small tube headers isn't an option.

Either way, installing headers on ANY FE in a Mustang is one of life's most frustrating experiences!!

[shelbydoug]

Wow! You've got my attention. What wouldn't fit with a manual transmission? Was it the clutch linkage or the transmission itself?

[2112]

Have you guys compared 1-3/4" to 1-7/8" headers on a Dyno? How about on a flow bench?

I have. The radius of the turn of the primary tube is more important than a tiny bit larger diameter. In a tight engine bay, the bigger the primary tube, the more aggressive the turn. More turbulence and less flow if too tight. You know, like an FE in a Mustang.

Competitively racing? Sure, it might make a difference. On the street? Seat of the pants? I don't think one could feel the difference between 536 hp and 526 horsepower.

Is it worth $3000 to not drag on the pavement and have 1.78943% more hp?

[shelbydoug]

 The od of the tubing primary should match the od of the exhaust valve. It isn't so much about ultimate hp. It's where the power peaks.

The smaller the tube, the lower the power peak. In an FE, the maximum torque is going to come in early. Like around 1500 rpm and pretty much stay flat all the way through it's useable power range. Probably not dropping until about 6000 rpm.

HP is going to be different. Depending on where you want your HP to peak is where you tune the headers to.

A set of tri-y's is going to peak early. Probably right around the magic 5252 rpm mark. Maybe even earlier? Individual tube header of the correct length (34 to 36") will more likely peak over 6000. Probably around 6500 with 2" primaries and 3-1/2" collectors. You can tune some with the length of the collectors also.

1-3/4" tubes will peak lower. I'd guess 5800 to 6000. For a street FE that would be about right.

My Hooker Super Comp headers were 2-1/8" primaries. Those peaked a little over 7,000. 7200 as I recall. That's way too much header for a box stock 428. Even a stock SCJ or a 427.

In order to use that header you need an honest high 7000 rpm engine.

Even a box stock 427MR will blow up at that number. That doesn't mean that you can't build it to run reliably at that rpm but they do tend to break a lot with that usage even with the best parts.

The 1-3/4" tri-y's are made simply for the ease of installation. The stock iron manifolds in these cars are just so badly restricting that any header will show a drastic improvement.

The Hooker street Super Comps size wise are a good compromise but it's at best a 6500rpm header and you'll feel power drop at 6000. It's main issue is the same as with all Hooker full length headers. The collectors are very low.

Now you could take that header and cut the primary tubes before they turn to the back and probably gain a full pipe diameter, 1-3/4". That's a huge difference to raise them but it's a huge amount of work even with an easy header installation.

In an FE Mustang, you could cross over the line into fully suicidal?

It's interesting how headers actually work. I think of it like playing a musical instrument like a trumpet or trombone. As you change the diameter of the tube and it's length, you change the frequency.

Have you ever noticed at the track when a car with a well tuned exhaust takes off or goes by how everyone freezes to listen to it? I do. Every car sounds just a little different but I generally enjoy the song.

Incidentally. Dyno pulls are generally inaccurate unless you are using the headers that you will use in the car. Using the shops dyno headers are overlooking a major factor in determining the amount of power that the CHASSIS of the car will permit because of exhaust restrictions.

[2112]

You can compare 2 different sets of headers on the same day, Dyno and tune.

It comes down to which compromise you are willing to live with. For me, in a 52 y/o non-race Mustang, I will give up maximum performance to not drag on the pavement.

[shelbydoug]

You can compare 2 different sets of headers on the same day, Dyno and tune.

It comes down to which compromise you are willing to live with. For me, in a 52 y/o non-race Mustang, I will give up maximum performance to not drag on the pavement.

[1967 eight barrel]

1/8 ID in no way could make a huge differece in flow. How the headers are made and how they scavenge would make all the difference. 

[shelbydoug]

Correct. The size of the pipe justs "tunes" them.

Make sure the headers you buy will fit with the original z-bar clutch components. The FPA tri-ys don't. You need a hydraulic clutch with those.

[tonys_shelby]

What brands fit so you don't have to change the z bar or drop the power steering pump items?

[67GT500#1594]

Wow! You've got my attention. What wouldn't fit with a manual transmission? Was it the clutch linkage or the transmission itself?

The drivers side rear tubes, based on my findings of engine images, blocked the z bar and clutch linkage. The headers were perfect for my app in every way! The forum member was great to work with and he was unsure of the fit as well. At the end of the day he was right on money wise but if I still had the modify the right side, I was taking a huge chance.

My car as with this car has a different engine to have fun with, while saving the concourse correct motor on a stand in the corner. As with any car mine has a history and the engine I've got has a storyline too. I've got a Tunnel Port that, while too much, was the ultimate wedge motor in 67! The thought was, build the car to "day 2" mods and that's where I've gone. It's very similar to a few other guys here on the forum too.

Now, a 496 CI, GT40 Dual Plane SK, hydraulic roller, updated TP is of course overkill, you'd kill all advancements by putting small tube headers on it. The engine is detuned and will make 610-620 HP/ TQ based on previous builds from the same builder. So yes, the engine will need it. I just wanted the engine to make street able power, effortlessly. It will probably scare the crap out of me!

I've got a local guy that I bought headers from that, well don't fit, so he owes me the redo. There's also REF in Arizona that makes custom headers that are said to be perfect but at $1800 or so pricing? Their headers do look VERY nice and don't scrub! He builds them to order on a actual Mustang front clip with your oil pan, bell housing deminsions too.

I'm still just working on sheet metal so I have time! I'll post pics of the REF headers.

[67GT500#1594]

REF headers. Pretty darn SEXY!!