exhaust manifolds vs headers

[72charger440]

 my friend is wondering for his 70 charger with a 440 six pack 4spd thats beening rebuilt should he keep the exhaust mans or put some money down and buy headers but,  he thinks that the factory exhaust manifolds will be just as good as headers and make more back pressure then headers will for more low end torque ,what does every one think he should do? hes runnin the same cam thats in my 440 an edelbrock perfomer rpm 1500-6500 with a .425 lift.

thanks

[defiance]

What's his build like?  Is it numbers matching & going back to factory appearance, or is modification par for the course?  Headers are a bit hard to miss if he's going for a resto look   My understanding is that manifolds will choke the flow, reducing the output quite a bit overall, but I think he's right that it will be a little bit better in the low end... 

[aifilaw]

There's a reason the cheapest $/hp upgrade is headers (aside from nitrous oxide of course).
That's because adding headers will add the most % power over any other upgrade except for adding cubic inches or portwork/replacement of cylinder heads. And even after those are done, it still adds tremendous power over the stock manifolds.
If you are going for a stock look get the HP manifolds if you can find them, they are about halfway in between a well matched set of headers and stock manifolds as far as power % added.
with a cam like that and an engine like that, just to put some numbers in comparison for him (since I don't know heads, work, cam specifics, intake, carb, et cetera). He's looking at the difference between making 300HP at 4000 RPM and 470 ft lbs of torque at 2500 RPM with stock manifolds, and making 350 HP at 4500 RPM and 500+ ft lbs of torque at 2500 RPM with headers.

[72charger440]

its not a numbers matching car it was a alpine white 70 charger 500 or se 383 4bbl 4spd, found the car 2 months ago in a salavage yard in az car was sittin on the ground had nothing no suspension nothin just  a shell almost  forgot whats the engines build. the  engine is a 72 440 block its  .30 over and has  71 440 six pack heads ,the edelbrock cam i mentioned, has a 6pack setup on it has a 76 cast crank has the factory 72 rods thats all i know, and has factory rockers /pushrods. but he keeps tellin me that the factory exhaust manifolds are better, but since what im being told/ hearing my 440 that has  headers is going 2 b way better then his six pack 440 with exhaust manifolds.

[Mike DC]

   
Realistically the stock manifolds won't feel weaker on a street cruiser just thumping around town at 2000-3000 rpm. 

But the difference at 4000-6000 rpm will be much more noticeable to the driver.  Maybe 25hp and 35 lb/ft at the top of the power pull on a decent slightly-modded 440 motor. 




Headers are very cheap power for what they deliver.  Either you want it or you don't.   

   

[Rolling_Thunder]

I have that same cam in my stroker...         it will be fun tuning the six pack with it...    I put that same cam in Chris Jacob's GTX - he's also running a six pack and it turned out to be a real screamer...

If you want the look go for headers - I just find manifolds easier to play with and realisticly headers are not worth the headaches to me - and as already mentioned on a street car it wont make much difference.

[Ghoste]

I'll propose an addendum to that and say that on a street car just being used to cruise around town they won't make much difference, open that street car up a little and they make a huge difference.

[375instroke]

Back pressure?  This is a term thrown around by people that haven't a clue as to what is happening.  Tell me, what is back pressure.  All I can think is that someone put 2-1/4" headers on their 350 and thought "What a turd.  The headers are too big.  The car is slower than with manifolds.  It must need more restriction to make power."  Manifolds get the exhaust out.  That's all.  Full length headers allow fluid dynamic principles to affect the efficiency of the exhaust cycle, and help the intake cycle also.  We can play with all the formulas we want, but we are still limited by our engine compartments and what headers are on the market.  There's plenty of info out on the internet to read up on.  Unless you have a small motor and use a huge primary, you will most certainly make more torque with headers than manifolds.  Headers are, however, more fragile than cast iron, usually rust, will probably leak, are perhaps louder, often hang down, have been known to burn plug wires and boots, are a pain to install, could burn up your starter, and if the starter does take a crap, it may be captured behind the header tubes.

[Rolling_Thunder]

yep - more power but a major pain in the ass to deal with if something ever goes wrong...          I had hooker super comps on my 440 in the Charger but there is a reason i have 2 sets of stock HP manifolds in my garage...    one set for the 440+6 for the Road Runner and another set for the 383 going into the Satellite.   

[badass]

Ill never forget the burns I got on my arms from my first set when I was 17 PSSSSsssttt.$50. blackjacks PSSSsssttt. :RantExplode:But I want to go faster, PSSSSsssttt Ouch! Damn starter, damn headers,

[Mike DC]

Back pressure?  This is a term thrown around by people that haven't a clue as to what is happening.  Tell me, what is back pressure.  All I can think is that someone put 2-1/4" headers on their 350 and thought "What a turd.  The headers are too big.  The car is slower than with manifolds.  It must need more restriction to make power."  Manifolds get the exhaust out.  That's all.  Full length headers allow fluid dynamic principles to affect the efficiency of the exhaust cycle, and help the intake cycle also.  We can play with all the formulas we want, but we are still limited by our engine compartments and what headers are on the market.  There's plenty of info out on the internet to read up on.  Unless you have a small motor and use a huge primary, you will most certainly make more torque with headers than manifolds.  Headers are, however, more fragile than cast iron, usually rust, will probably leak, are perhaps louder, often hang down, have been known to burn plug wires and boots, are a pain to install, could burn up your starter, and if the starter does take a crap, it may be captured behind the header tubes.

Very true. 

The talk about header sizing & backpressure is relevant to race cars where everything is uncompromised.  But on most street car applications, the stock manifolds are so restrictive that any kind of bigger pipes are an improvement.

[69bronzeT5]

If he decides to put headers on it, make sure he puts a good high torque mini starter in! Replacing the starter with headers on is not fun at all!