74 Dart. Headers vs manifold.

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D4dartswinger

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So I have a 74 Dart swinger(318, 4 barrel carb). It’s my daily driver and now for the next year I’ll have to drive it 20 miles to and from school In traffic both ways . Takes about a hour. I currently have **** mileage already and was in an accident and rebuilt the front end and now have to make a decision between manifolds of headers. So I’m just trying to go the route of which will improve my gas mileage. Would appreciate any help
 
Headers aren't going to improve your gas mileage. They probably won't hurt it either, but if it's an otherwise stock 318 they're not going to change a lot for you. Maybe a small increase in mid-range and up horsepower, but probably not something you'd notice.

And unless you're going to buy a set of TTi's or Doug's D453's, headers are probably going to be a much bigger headache than any benefit you'll see.

What's "****" mileage? With a relatively stock 318 you should be able to get 15-18 mpg depending on your gearing. If it's any less than say 12-13 mpg you probably have a tuning issue, unless it's got a big cam in it.

We'd need to know more about your engine and gearing set up to help much more than that.
 
What you will go through adding headers will end up actually making very little difference.
In your specific circumstances I would try and get something like the FItech fuel injection because you need to get places regularly with decent gas mileage.
I'm not just throwing fuel injection out there for the fun spending someone elses money either, just in case that crossed your mind.:D
 
Headers aren't going to improve your gas mileage. They probably won't hurt it either, but if it's an otherwise stock 318 they're not going to change a lot for you. Maybe a small increase in mid-range and up horsepower, but probably not something you'd notice.

And unless you're going to buy a set of TTi's or Doug's D453's, headers are probably going to be a much bigger headache than any benefit you'll see.

What's "****" mileage? With a relatively stock 318 you should be able to get 15-18 mpg depending on your gearing. If it's any less than say 12-13 mpg you probably have a tuning issue, unless it's got a big cam in it.

We'd need to know more about your engine and gearing set up to help much more than that.
Well it has a stage 1 cam, 650 edelbrock carb, performer 2 manifold. It was recently rebuilt. Probably less than 1000 miles on it
 
What you will go through adding headers will end up actually making very little difference.
In your specific circumstances I would try and get something like the FItech fuel injection because you need to get places regularly with decent gas mileage.
I'm not just throwing fuel injection out there for the fun spending someone elses money either, just in case that crossed your mind.:D
Hmmm I see well I just bought the 4 barrel carb so I kinda have to stick with that for a while ($$). One of my exhaust manifolds broke so I’m having a little trouble finding another and I was advised of getting headers to improve everything and how it was overall beneficial to the car
 
What you will go through adding headers will end up actually making very little difference.
In your specific circumstances I would try and get something like the FItech fuel injection because you need to get places regularly with decent gas mileage.
I'm not just throwing fuel injection out there for the fun spending someone elses money either, just in case that crossed your mind.:D

Definitely!

More money spent, sure. Although if you’re doing TTI’s and a full exhaust maybe not that much more money depending on the current fuel system set up and FI conversion used.

But fuel injection would be the best way to improve fuel economy, assuming you’re already tuned correctly and don’t have some kind of engine problem that’s hurting mileage. For a driver it also has some nice advantages beyond the best mileage you’re going to get. No warm up time like with a carb, which makes it easier to drive all the time and improves your gas mileage (not sitting around idling with the choke on). In theory, more accurate tuning, which again helps the mpg’s but also might improve drive-ability, especially if the current tune isn’t quite right. Should be less fuel smell too, although some people like the “old car smell” that definitely includes some unburned fuel.

Well it has a stage 1 cam, 650 edelbrock carb, performer 2 manifold. It was recently rebuilt. Probably less than 1000 miles on it

Stage 1 cam? Ok. Doesn’t mean anything to me without specs or a part number.

Recently rebuilt doesn’t mean it’s properly tuned either, or that it doesn’t have an issue. Less than 1,000 miles might actually worsen fuel mileage a little, engines loosen up a little as they break in, so less friction loss compared to brand new. That’s a small difference though.

And what kind of fuel mileage are you actually getting?

Hmmm I see well I just bought the 4 barrel carb so I kinda have to stick with that for a while ($$). One of my exhaust manifolds broke so I’m having a little trouble finding another and I was advised of getting headers to improve everything and how it was overall beneficial to the car

Which one? I’ve got a couple extra exhaust manifolds.

Headers can improve efficiency a bit, but that usually translates to more power, not better mileage. And with a mild 318 it won’t be much power either...
 
Your mileage will go down because you are going to hit the gas harder to hear the cool sounding exhaust. They adds 50 audio horsepower.

Headers are more trouble than they are worth unless you've built your engine. A stock daily driver is just fine with stock manifolds.
 
adding $1000 EFI wont improve gas mileage either, unless your way out of tune on a carb. 14.7 stoich is stoich: from a carb or an injector. Headers usually lean out a manifold tuned carb. Dyno results on a tuned carb over EFI are not night and day, but cold start driveability is. Carters are usually pretty flat across the curve AFR wise. Take your car to a tuneup place with an exhaust gas analyzer and have them tune the carb. Or buy a $150 wideband and a strip kit and do it yourself and still have the ultimate carb tuning tool in your toolbox. If you want better fuel economy, increase your compression ratio, cam down in duration and go to a shorter rear end.
 
If your priority is fuel economy, then you probably shouldn’t be starting with a 40+ year old iron that has a V8. Best to buy a modern 4 cylinder econo bucket that will give you at least double to maybe three times the fuel economy you’ll ever get out of the Dart.

Driving an old car is great but don’t fool yourself into thinking the old car can also be really fuel efficient.
 
adding $1000 EFI wont improve gas mileage either, unless your way out of tune on a carb. 14.7 stoich is stoich: from a carb or an injector. Headers usually lean out a manifold tuned carb. Dyno results on a tuned carb over EFI are not night and day, but cold start driveability is. Carters are usually pretty flat across the curve AFR wise. Take your car to a tuneup place with an exhaust gas analyzer and have them tune the carb. Or buy a $150 wideband and a strip kit and do it yourself and still have the ultimate carb tuning tool in your toolbox. If you want better fuel economy, increase your compression ratio, cam down in duration and go to a shorter rear end.

Yeah if you watch a well tuned carb on an air fuel gauge compared to EFI it's a totally different story. Even well tuned carbs aren't capable of the kind of consistency and accuracy that a decently tuned EFI system can give. Maybe on a dyno it's not a "night and day" difference, but dyno's are about maximum power, not about maximum fuel mileage as driven on the street or even the best driveability on the street. Two completely different things. All you're getting a good picture of on a dyno is WOT, it's a tiny component of a carb's overall tune and a part of the tune that's barely even going to be used on a driver. It's easy to tune WOT compared to tuning all the transitions, that's where you lose efficiency. It's not like a carb will hold your AFR at 14.7 all the time. Not even close. And that's where EFI improves mileage- it's about how consistent the AFR is, and EFI does a much better job on average if you look across the board.
 
If your priority is fuel economy, then you probably shouldn’t be starting with a 40+ year old iron that has a V8. Best to buy a modern 4 cylinder econo bucket that will give you at least double to maybe three times the fuel economy you’ll ever get out of the Dart.

Driving an old car is great but don’t fool yourself into thinking the old car can also be really fuel efficient.
Well originally I had a 2000 Malibu got into an accident and now that car is gone. I already had the dart and wasn’t on planning on driving further than my city for the most part but I’m starting school soon and for a solid year I’ll be doing the 9-5, 5 days a week. I’m contemplating just searching for a $2,000 car that can get me to and from school and keep the dart for when I have freer time. If that’s the case, should I just go with the headers? Can get a set of headers for 250
 
Definitely!

More money spent, sure. Although if you’re doing TTI’s and a full exhaust maybe not that much more money depending on the current fuel system set up and FI conversion used.

But fuel injection would be the best way to improve fuel economy, assuming you’re already tuned correctly and don’t have some kind of engine problem that’s hurting mileage. For a driver it also has some nice advantages beyond the best mileage you’re going to get. No warm up time like with a carb, which makes it easier to drive all the time and improves your gas mileage (not sitting around idling with the choke on). In theory, more accurate tuning, which again helps the mpg’s but also might improve drive-ability, especially if the current tune isn’t quite right. Should be less fuel smell too, although some people like the “old car smell” that definitely includes some unburned fuel.



Stage 1 cam? Ok. Doesn’t mean anything to me without specs or a part number.

Recently rebuilt doesn’t mean it’s properly tuned either, or that it doesn’t have an issue. Less than 1,000 miles might actually worsen fuel mileage a little, engines loosen up a little as they break in, so less friction loss compared to brand new. That’s a small difference though.

And what kind of fuel mileage are you actually getting?



Which one? I’ve got a couple extra exhaust manifolds.

Headers can improve efficiency a bit, but that usually translates to more power, not better mileage. And with a mild 318 it won’t be much power either...
Well I kinda wanted to keep the old loud idle and sound of the car. I was just wondering if headers would help my gas situation or hurt it. But after some thought I’m going to look for a little beater of a truck or something for cheap. This is my first older car, only had a 2000 Malibu before so I’m learning everything as I go
 
adding $1000 EFI wont improve gas mileage either, unless your way out of tune on a carb. 14.7 stoich is stoich: from a carb or an injector. Headers usually lean out a manifold tuned carb. Dyno results on a tuned carb over EFI are not night and day, but cold start driveability is. Carters are usually pretty flat across the curve AFR wise. Take your car to a tuneup place with an exhaust gas analyzer and have them tune the carb. Or buy a $150 wideband and a strip kit and do it yourself and still have the ultimate carb tuning tool in your toolbox. If you want better fuel economy, increase your compression ratio, cam down in duration and go to a shorter rear end.
Ya I think I will take it to a performance center. I took it once before when I first started the new engin me but it ended up being my shitty 2 barrel so try tuned the new 4 barrel. So switching to headers would need some additional tuning?
 
Cheap headers are just that. They will need to be beaten to crap to fit in and then they will probably scrape/bottom out on everything bigger than a pebble.
 
Anything more than a good tune up your wasting money looking for mileage.
Depends on how much you drive but even to recoupe a $1000 could take 3-5 years. Cheaper just to dump it into the tank.

Now if your looking gor added performance with little to no loss in mpg thats different.

Headers and a good exhaust should add a nice boost in performance across the power band. And set the stage for future up grades 4bbl and small cam etc..
 
Your best bet IMO is to swap out that Stage I racing cam, for something more like the stocker.or even less. Just for the year/timeyouareinschool mind you.
 
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... Even well tuned carbs aren't capable of the kind of consistency and accuracy that a decently tuned EFI system can give. .... It's not like a carb will hold your AFR at 14.7 all the time. Not even close. And that's where EFI improves mileage- it's about how consistent the AFR is, and EFI does a much better job on average if you look across the board.

I agree but you got to give a carb a little more credit than that. It can hold a pretty stable A/F ratio considering its in a static tune and has to function over a wide operating parameter. look at this QFT 750 carb on a Chevy 377. Not bad, not closed loop EFI good but would it warrant a $1000 change in mileage? Give it is on a dyno pull and not on the street......
dynosheet.jpg
 
In town mileage is hard to increase, with billions of dollars in research over the last 4 decades from manufacturers . Cars similar to our A Bodies don't produce all that much more mpg then we got. We get mid teens they get mid-high teens depending on the car. My jeep gets low teens.

I spent $5000 on efi/ignition at best I may gain a couple mpg. And I plan on this car car to be 9 months out the year daily driver but it probably would take 15 plus years to recoupe that cost. My main goal is driveability then performance with and eye on mileage.

Highway mileage you can gt decent increase and if do enough driving could recoupe in 5 or so years. But all in all if mileage is your primary reason for mods its cheaper to dump it into the tank. A gain of 3 mpg is only like saving around $300 a year.
 
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