long tube headers advise/exhaust help please

[marty79]

building a 90 F150 with the 302 and I got some long tube headers for it. My question (as I've never used them before) is for performance, will they work better with true duals or converge into single kinda like factory does? I'd rather get performance out of them more than sound as I'm more focused on that with all the other engine work I'm doing to it. Thanks for all the help and advise!
These are them...pretty exited about this truck build. Oh and also what kinda high heat paint is good to coat them with even though they come coated already would like to make sure it lasts i guess.

 

[Fabrik8]

Those are coated? Coated with what?

 

[Croatan_Kid]

Dual with an X pipe or a muffler with an internal crossover. 2.5" pipe should do just fine.

Rustoleum makes an extreme high temp paint that sprays more like powder. I've used it on a lot of exhaust parts and it holds up really well...especially for 5 bucks a can. 2 cans will give you good coverage on longtubes. They even make a primer for it.

 

[marty79]

Those are coated? Coated with what?

oh I don't know I figured they were but maybe that's just some cheapo factory paint lol

 

[marty79]

Dual with an X pipe or a muffler with an internal crossover. 2.5" pipe should do just fine.

Rustoleum makes an extreme high temp paint that sprays more like powder. I've used it on a lot of exhaust parts and it holds up really well...especially for 5 bucks a can. 2 cans will give you good coverage on longtubes. They even make a primer for it.

being 2wd, I seem to have lots of room so for the X pipe, that goes as close to the front as possible right?

 

[Croatan_Kid]

Doesn't particularly matter. Mine is in my muffler out towards the back of my truck. Still made a noticeable difference from my previous exhaust setup.

 

[marty79]

well sounds like duals is the way to go then.
One more question I forgot about. The factory exhaust has 1 O2 sensor right at the bottom of both down pipes where they meet and there's a little connector piece going from one pipe to the other with sensor in the middle of that connector piece.
With these headers, what's the best way to mount the o2sensor? just one side good enough? never encountered this type of setup, thank you

 

[Fabrik8]

well sounds like duals is the way to go then.
One more question I forgot about. The factory exhaust has 1 O2 sensor right at the bottom of both down pipes where they meet and there's a little connector piece going from one pipe to the other with sensor in the middle of that connector piece.
With these headers, what's the best way to mount the o2sensor? just one side good enough? never encountered this type of setup, thank you

IF you're going to do an H-pipe (like the stock exhaust), keep the crossover pipe short and put the O2 sensor in the crossover pipe (like the stock exhaust). Make the crossover pipe the same diameter as the pipes it joins to. Place the crossover pipe somewhere between 0.5 and 1.5 feet from the collectors if possible, ideally the same exhaust length away from the engine as the stock exhaust. The placement, length and diameter of the crossover pipe all have an effect on the torque band, but I wouldn't worry too much about it for a low-powered truck.

An X-pipe will give power higher up the RPM range than a H-pipe, and it's not as simple to make as an H-pipe, so I'd just do a H-pipe. Putting the O2 sensor at the X can also affect tuning sometimes, as the exhaust velocity in the crossover of an H is different than the velocity of the X. If the stock ECU was tuned for the stock H exhaust, the X might not be a drop-in replacement. Some vehicles are different than others, and I have no idea about how a 27 year old Ford will respond to that. Probably OK, because Ford's OBD1 ECUs were really crude back then, but again the H is the very simple solution. For the amount of power that the truck is putting out, there isn't going to be a noticeable difference between an H and an X, even when the X or H is properly tuned.

 

[marty79]

IF you're going to do an H-pipe (like the stock exhaust), keep the crossover pipe short and put the O2 sensor in the crossover pipe (like the stock exhaust). Make the crossover pipe the same diameter as the pipes it joins to. Place the crossover pipe somewhere between 0.5 and 1.5 feet from the collectors if possible, ideally the same exhaust length away from the engine as the stock exhaust. The placement, length and diameter of the crossover pipe all have an effect on the torque band, but I wouldn't worry too much about it for a low-powered truck.

An X-pipe will give power higher up the RPM range than a H-pipe, and it's not as simple to make as an H-pipe, so I'd just do a H-pipe. Putting the O2 sensor at the X can also affect tuning sometimes, as the exhaust velocity in the crossover of an H is different than the velocity of the X. If the stock ECU was tuned for the stock H exhaust, the X might not be a drop-in replacement. Some vehicles are different than others, and I have no idea about how a 27 year old Ford will respond to that. Probably OK, because Ford's OBD1 ECUs were really crude back then, but again the H is the very simple solution. For the amount of power that the truck is putting out, there isn't going to be a noticeable difference between an H and an X, even when the X or H is properly tuned.

Thank u sir. H pipe will do with duals. And motor isn't going to be stock, not crazy but good bit of power adds when all done. Thanks for help

 

[Hurley]

Best advice you can get is to choose your engine build parts and tuning to all compliment each other - exhaust included. If your (realistically) only going to be in the 300hp range, there's nothing wrong with a good 2-1 merge and 3" single exhaust with a decent muffler.

 

[GotWood]

Best advice you can get is to choose your engine build parts and tuning to all compliment each other - exhaust included. If your (realistically) only going to be in the 300hp range, there's nothing wrong with a good 2-1 merge and 3" single exhaust with a decent muffler.

And it makes a good sleeper with single exhaust!

 

[ol'Jeeps]

Rule of thumb... duals, big pipes, h-pipes, all for top end power. Small tubes, single exhaust via an x-merge or a 2 into 1 merge, for low end torque.

Big pipes/duals will kill a 302. It wont fall out a tree until around 5000 rpm! H-pipes, called balance tubes, make the exhaust think it has reached atmosphere near the end of the headers. Again, bad for low end. Good for top end.

302, stock or mild built, would probably like a 1 1/2" header tube to a 2" (2.5?) collector. 2" pipes back around half the total exhaust length, or less, then merge into single 2".

The more you open up the exhaust on a 302, the more you wont like how it drives...either on the street and especially on the trail. (Unless you plan to keep it above 4500 rpm!)

 

[GotWood]

Rule of thumb... duals, big pipes, h-pipes, all for top end power. Small tubes, single exhaust via an x-merge or a 2 into 1 merge, for low end torque.

Big pipes/duals will kill a 302. It wont fall out a tree until around 5000 rpm! H-pipes, called balance tubes, make the exhaust think it has reached atmosphere near the end of the headers. Again, bad for low end. Good for top end.

302, stock or mild built, would probably like a 1 1/2" header tube to a 2" (2.5?) collector. 2" pipes back around half the total exhaust length, or less, then merge into single 2".

The more you open up the exhaust on a 302, the more you wont like how it drives...either on the street and especially on the trail. (Unless you plan to keep it above 4500 rpm!)

If what you say it's true, then a desiel would only have a single exhaust, maybe 3", to take advantage of the low end torque and low RPM? All of my friends have a 5"exhaust on theirs!

 

[Hurley]

^naturally aspirated VS turbo - design considerations go out the window when trying to cross-compare the two.

you're doing a few things with exhaust design on a NA (or supercharged) engine:
- reduce restriction
- improve scavenging
- capitalize on exhaust pulse cadence, which in a way is a synthesis of the above two.

on a low RPM engine, the above can be managed with long primaries and smaller diameters - headers only. once you get a few feet past the collector you're only out to control/reduce sound, vibration and restriction. H and X pipes tie into my above list by exposing the exhaust pulses from one bank to another on a cross-plane crank. (The same can be accomplished with a 180deg header)

 

[Fabrik8]

Rule of thumb... duals, big pipes, h-pipes, all for top end power. Small tubes, single exhaust via an x-merge or a 2 into 1 merge, for low end torque.

That's backwards from conventional wisdom, at least as far as the X- versus H-pipe goes. X is generally for top end, H generally for low end, because of the less efficient H crossover creating more backpressure between banks. X is a more efficient design, which tends to shine when the H-pipe really falls off in power.

 

[ol'Jeeps]

Jim, Your friends are wrong if they think a bigger pipe makes more torque. A Diesel is no different in this respect from a gasoline engine. Generally, making exhaust larger on a diesel is to build horsepower and extend the power farther up the rpm range. The bigger pipe does nothing to help torqe. Torque will naturally rise some with the increase in power. But as the pipe gets bigger you will see the torque curve flatten or drop off as horsepower rises. And yes. all the big ass diesel pulling trucks, I recall have a single exhaust coming thru the hood! And every piece of diesel heavy equipment I have ever seen has a single exhaust...nat, turbo or supercharged! BTW... 2017 Ford Power Stroke makes "industry leading" 925 LbFt of torque thru a 3.5" single exhaust! (@mcutler ) Oh and you will know this...How many pipes on them big ol' fire trucks!

The difference between an H pipe and a merge or a 180 header is the fact that the 180 or merge actually merges the exhaust flow. Taking advantage of the pulses from other cylinders to improve flow. An H pipe does noting but create a pressure drop by equalizing the pressure between pipes.This makes the exhaust think it has reached atmosphere The pressure change also disrupts the pulses so the pulses cant do anything to help the flow of the exhaust in the other pipe such as a true merge pipe will.

Your wrong about the rest of the exhaust system. The entire system is part of the exhaust flow management. Pulses, back pressure, heat, all are factors in exhaust tuning.

 

[ol'Jeeps]

That's backwards from conventional wisdom, at least as far as the X- versus H-pipe goes. X is generally for top end, H generally for low end, because of the less efficient H crossover creating more backpressure between banks. X is a more efficient design, which tends to shine when the H-pipe really falls off in power.

Nope. We ran merge pipes or crossovers on short track and up thru the mile and a halfs. H pipes were only run at the superspeedways

 

[Hurley]

Torque will naturally rise some with the increase in power. But as the pipe gets bigger you will see the torque curve flatten or drop off as horsepower rises.

"Power will naturally rise with the increase in torque and rpm"


And the only concern with exhaust post turbo is to reduce heat retention and backpressure

 

[ol'Jeeps]

"Power will naturally rise with the increase in torque and rpm"...

Not sure what that means, but Horsepower increases with RPM until maximum HP is reached. Somewhere on that graph, the Torque will peak then flatten and/or decrease as RPM continues to increase to peak horsepower. Cam and exhaust will determine where that torque peak is and how sharply in decreases.

...And the only concern with exhaust post turbo is to reduce heat retention and backpressure

Kinda what I said when I said, "The entire system is part of the exhaust flow management. Pulses, back pressure, heat, all are factors in exhaust tuning."

But honestly, I know little of turbo systems. I most likely would not have jumped into this discussion if it was about a turbocharged 302!

 

[Fabrik8]

"Power will naturally rise with the increase in torque and rpm"

That's because HP is calculated from torque and RPM.

 

[Fabrik8]

Nope. We ran merge pipes or crossovers on short track and up thru the mile and a halfs. H pipes were only run at the superspeedways

I understand what you're saying, and it makes sense, but well-tuned race exhausts on race engines (that operate for extended periods in a fairly limited RPM band at full power) is not the same as a street car. It's all about operating conditions, and how well tuned the exhaust system is for those operating conditions.
The crossovers have an effect on a much broader RPM range (best and broadest power for most tracks, including short and intermediates), and the H pipes are able be be tuned for the narrower RPM range that is somewhat specific to superspeedways. Still though, it's odd to think that a H-pipe would work as well as an X-pipe on a superspeedway, given the high RPM where a X-pipe is generally much more efficient. I think I'm remembering that correctly, could be totally wrong though...? I seem to remember people running X-pipes on superspeedways too, and some people running H-pipes on shorter tracks, so that part is hazy. I don't know the history of who started using what and when, and when X-pipes first came on the scene, I just know that most everyone is using X-pipes now.

In a street car, that narrow RPM range for a H-pipe is generally at low RPM, and from that point onward you're losing power over what the more efficient and broad range of power that a X-pipe adds.

 

[Hurley]

@ol'Jeeps im busting your balls about TQ vs HP, and how many do not know they are directly related (for those who don't, HP = (torque x RPM)/5252 )

 

[ol'Jeeps]

I did not know that formula. We always just put em on the Chassis Dyno rig and kept building and switching pipes until we liked what we saw! Torque and/or HP numbers!

... I don't know the history of who started using what and when, and when X-pipes first came on the scene, I just know that most everyone is using X-pipes now....

Might be, now. I was there when the merge pipes first showed up in NASCAR. (I believe it was crew chief Runt Pitman [cant remember the engine builder] in the #4 Kodak car at Daytona). We ran them extensively on our Bush cars, along with common boom tubes, etc. The last couple of years I worked in the Truck series, On the speedways, and some of the faster mile and a halfs, we were running H pipe duals, out each side, or H pipe out the left side with separate boom tubes. The H pipes were located directly after the header collectors.

 

[marty79]

HOLY CRAP....I know more about exhaust now than ever dreamed to know!
I'm also more lost than I was before lol. I'm building this ford to just be a nice mild street truck that will look good, sound good, and have some fun driving with good amount of extra umph readily at the pedal while not trying to take a decade to build either hehe.
the headers are 1.5" with 2.5"collectors...since it's 2wd, it would be easier for me to run duals bending the exhaust myself (friend has nice pipe bender) rather than trying to do the merge into single like factory so this is what I would like to stick with IF from what I'm reading will still suffice for what I'm doing...and then add a H pipe to that withing a foot from the collectors?? thank you all for your help and input but just making sure I have a plan that is best....

302, stock or mild built, would probably like a 1 1/2" header tube to a 2" (2.5?) collector. 2" pipes back around half the total exhaust length, or less, then merge into single 2".

so try and stick with this is the best plan...suppose would be easier to bend the pipe half way back than trying to bend them to connect up front like factory

 

[marty79]

if it was about a turbocharged 302!

this is still on the back burner if I really wanna make a hot rod truck...kinda depends on how "funds" go