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Discussion Starter · #1 ·
I was thinking about putting a set of headers on my 4.7, but I don't really like the idea of shorty headers. So my idea was to buy a pair of shorties. Cut the collectors off. Weld on some longer tubes with some new collectors on the end and make a pair of long tube headers.

So my Questions are......
Is there any reason this would not work?
Are any of the 4.7 headers made equal length and does it matter?
How do I figure out the correct length to make them?

I also thought about making them stepped or tri-y but that my be getting to complicated.
 

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I was thinking about putting a set of headers on my 4.7, but I don't really like the idea of shorty headers. So my idea was to buy a pair of shorties. Cut the collectors off. Weld on some longer tubes with some new collectors on the end and make a pair of long tube headers.

So my Questions are......
Is there any reason this would not work?
Are any of the 4.7 headers made equal length and does it matter?
How do I figure out the correct length to make them?

I also thought about making them stepped or tri-y but that my be getting to complicated.
Headers are simple. their job is to carry exhaust gases away. there's really no wrong way to make a header. as long as it clears everything, and doesn't leak at the welds, then it'll work.

as far as whether or not equal length primaries matter or not...if your after every last hp that you can get, then yes, it matters, as they all need t obe the same length. but if all you want is a good quality header that flows better than a manifold, then no, it doesn't matter. my truck made 505hp and 535 lbs torque, and my headers are not equal length--they are "whatever it had to be to fit" so while I made good power without equal primaries...I could have probably picked up maybe 3 or 4 HP with equal length primary tubes--maybe even 5Hp. --in my case, not enough to matter. in a high dollar race machine that needs every last .01 in ET...yea, it would matter

now, if you want optimum performance...then you're opening a can of worms there that I don't think you're ready to get into.

your first step would be to determine which RPM you want peak power, which will be largely determined by the rest of your combo--heads, intake, cams, compression, stall on your converter, rear gear ratio, etc.

once you know that, then you need to get on the internet and find some formulas or charts to determine what length and size primary tube will give you peak power at the RPM you want. THEN your next step is to find a way to route all 8 tubes so that they are the same length, and still clear everything.

or, you could just simply fabricate some long tube primaries and whatever they end up as, is what you get...but if that's all you're going to do...then why not just run the stuff that's already available?
 

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There are no long tubes for the 4.7.:( Only shorties.
I realize that, but unless your going to go through the hassle of figuring out where your peak power should be based on your cams, stall, gears, etc. and then calculating the diameter and length of the primaries needed to maximize power at that particular RPM, and build each one to the same length...you're really not going to gain anything. random and different length "long tubes" will probably be equal in power to random and different length "short tubes" ...if not worse. the short tubes I've seen at least appear to be equal length.
 

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Not to mention the fact that the 4.7 is a small displacement motor, and not known for low RPM torque...it likes to rev...it needs to rev to make power, which means you'd want shorter headers anyway.
 

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Okay I thought you were saying that why bother making longtubes when they are already around. As for the shorties being the same length I know my Gibsons are no were near equal lengths and I was disappointed about that:(.
 

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i agree with Cuda i dont think people realize how hard it is to make a set of headers. yah jessi james makes them in 30 minutes on monster garage and they always look killer but he makes this shit look easy. im not to scared to take on a project like this and have whought about it many times but just dont have the time to doo it. go with the shorties you wont regret it and beleive me you could spend all the time in the world working out the formula for the long tubes but in the end if it dosnt perform right you gonna be pissed.
 

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Discussion Starter · #8 · (Edited)
I didn't think 230 hp at 4600 rpm and 290 ft lbs at 3600 was high revving. My plans for the engine are '08 intake manifold, HO cams, and maybe a 72mm TB. Oh and my Dakota is a manual so no torque converter to worry about.
 

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I had nothing to compare them to but in the early 70's Mickey Thompson designed an equal length header where the tubes entered a collector/canister that formed a chamber. This way he did not have to have them look like a pile of spaghetti. The order in which they entered the collector/canister was also important as it affected the exhaust scavenging.

If you want lots of low end torque you can go as small as 1 5/8 primaries and 2 1/2 collector. Unless you are going all out you are better off under size than too big. I had a Roadrunner w/383 and a set of Headers by Ed and he insisted on using 1 5/8 primaries. Got lots of torque and many trophies with that car.
 

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I didn't think 230 hp at 4600 rpm and 290 ft lbs at 3600 was high revving. My plans for the engine are '08 intake manifold, HO cams, and maybe a 72mm TB. Oh and my Dakota is a manual so no torque converter to worry about.
my point was that the 4.7 is a small motor. it will never be a low rpm torque monster, and is best suited to high revs. sure the factory cams might put it's peak torque at 3600 rpm, which isn't "high" but its still not a low RPM torquer either.

when Iwas towing with mine, in order to get it to maintain speed going up a long hill, I had it at WOT, in 3rd gear spinning 4500rpm, and that was with 3.92 gears My dad was behind me with a similar load but was towing with a stock GM350, and was puring along at 2500 rpm with the OD off.

again, the 4.7 is a small displacement, low torque motor. trying to build it for torque is not where it's best suited...its best suited as a high RPM motor, in which case, shorty headers are ok.

remember, torque is simply force x distance from pivot point. the longer the stroke in an engine, the longer the pivot point, the more torque it will make. 4.7s are short stroke motors...not best for torque, but short stroke motors make for very fast reving motors, because the piston has less distanct to travel in the same amount of time, and therefor, is less stressful on the internals, and easier to spin faster.

I had a little R/C airplane motor that was like, .049CC? the damn piston was the size of a pencil eraser!:jester: I think that thing RPMd at like 30,000RPM simply because the stroke was so small
 

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Not to mention the fact that the 4.7 is a small displacement motor, and not known for low RPM torque...it likes to rev...it needs to rev to make power, which means you'd want shorter headers anyway.
You are right. I'm still living in the past.

It will still work on a 383 Cuda.:wave:
 

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The theory behind equal length headers is to ensure that exhaust pulses from multiple cylinders do not reach the collector at the same time causing spikes in the exhaust pressure. I also have a 5.0 Mustang for which equal length shorties are available. They look like spaghetti and are a PITA to work with. All dyno tests show they are good for a couple HP more but are not worth is compaired with the headach they cause working with them. They are no true equal lenght headers for our application.
 

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Discussion Starter · #13 ·
Makes sense. I just figured they only made shorty headers for the 4.7 because there wasn't enough call for the long tube headers and they were easier to install with the stock y-pipe. I was just wondering why I have never seen a race engine of any bore, stroke or rpm with short tube headers?
 

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my point was that the 4.7 is a small motor. it will never be a low rpm torque monster, and is best suited to high revs. sure the factory cams might put it's peak torque at 3600 rpm, which isn't "high" but its still not a low RPM torquer either.

when Iwas towing with mine, in order to get it to maintain speed going up a long hill, I had it at WOT, in 3rd gear spinning 4500rpm, and that was with 3.92 gears My dad was behind me with a similar load but was towing with a stock GM350, and was puring along at 2500 rpm with the OD off.

again, the 4.7 is a small displacement, low torque motor. trying to build it for torque is not where it's best suited...its best suited as a high RPM motor, in which case, shorty headers are ok.

remember, torque is simply force x distance from pivot point. the longer the stroke in an engine, the longer the pivot point, the more torque it will make. 4.7s are short stroke motors...not best for torque, but short stroke motors make for very fast reving motors, because the piston has less distanct to travel in the same amount of time, and therefor, is less stressful on the internals, and easier to spin faster.

I had a little R/C airplane motor that was like, .049CC? the damn piston was the size of a pencil eraser!:jester: I think that thing RPMd at like 30,000RPM simply because the stroke was so small
With a that being said, what's the best way to squeeze out a little more torque out of the little 4.7 lol? Rear end gears?
 
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