I'm wanting to ditch my OLD low hanging headers, are these manifolds worth it?

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AlaskaJeff

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Would these do as good as a HP OEM set of manifolds? How much HP gain or loss over headers do you think they would be? My 360 is a mild build, nothing radical. I'm wanting to put a whole new exhaust system (within a budget) in the car and just exploring options.
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1968-74 Dodge Plymouth 340 360 318 Exhaust Manifold Pair Clean Dart Duster Demon | eBay
 
you can get 2.5 head pipes from TTI for those manifolds. You can also get better headers that don't hang low, like Doug's.
 
you can get 2.5 head pipes from TTI for those manifolds. You can also get better headers that don't hang low, like Doug's.
I am aware there is a bunch of stuff out there. Unfortunately living in Alaska and shipping an already "out of my budget" exhaust system here is a firm NO GO. I will end up taking the ole' Duster to a local reputable muffler shop for the new system. Just exploring the options. I guess I'm really wanting to know IF these manifolds would rob enough HP to make a difference over headers.
 
I am aware there is a bunch of stuff out there. Unfortunately living in Alaska and shipping an already "out of my budget" exhaust system here is a firm NO GO. I will end up taking the ole' Duster to a local reputable muffler shop for the new system. Just exploring the options. I guess I'm really wanting to know IF these manifolds would rob enough HP to make a difference over headers.
headers will provide more hp, the difference will be how mild or wild your engine is built...
 
Hard to put a number on it, but how is that top manifold going to have anywhere near as good of flow as a header? And they won’t be as good as HP manifolds either.

how high do you rev the engine. How do you drive? 1/4 throttle put putting? Or stop light Grand Prix?
 
Hard to put a number on it, but how is that top manifold going to have anywhere near as good of flow as a header? And they won’t be as good as HP manifolds either.

how high do you rev the engine. How do you drive? 1/4 throttle put putting? Or stop light Grand Prix?
I figured that they would be more restrictive. As far as driving style....I'm usually somewhere in between Put Put & Grand Prix with an occasional generous application of the go pedal. Once I get the trans slip issue resolved I'd like to be more Grand Prix leaning :thumbsup:
 
Any header is an improvement over manifolds. How much are you willing to give up by going to manifolds?
 
Any header is an improvement over manifolds. How much are you willing to give up by going to manifolds?
I've seen threads about the 340 HP manifolds and how some believe they are better than headers. Wondering if there is a basis for that opinion. OR is it just their opinion?
 
Richard Holdener did a manifold v header comparison on a mildly cammed LS engine. Headers were about 10 hp better throughout the rpm range.
 
Ditch the headers for a street car. Headers suck on an "A" body. Even worse if you have power steering.
 
Those are 318 stock manifolds. You can put a ten foot diameter pipe on them and it won't make a hill of beans difference, since they are attached to about a 1 7/8" outlet. Don't waste your money on big diameter pipe if you're not going to at least find a set of the 68-71 340 manifolds so you can take advantage of the bigger pipe.
 
Hedman block hugger shorties, or 68-71 340 HI PO manifolds. Either way they are gonna cost you. They now make repop 68-71 340 manifolds. No factory markings though. About $600 new.
 
Hedman block hugger shorties, or 68-71 340 HI PO manifolds. Either way they are gonna cost you. They now make repop 68-71 340 manifolds. No factory markings though. About $600 new.
The Hedman shorties are a little over $300 with FREE shipping on Amazon right now. Close to 1/2 the price of the HI PO manifolds AND I've got to factor in shipping to AK!! Trying to stay within a budget....
 
The only problem w the hedman shorties, and I have a set that i test fit, but did not install is making the pipes fit around the steering linkage. TXstang84 has a 72 scamper with a magnum teener in it. He is running them. Pipes on it are a little creative to get around the steering. With the hi po ones you can buy head pipes from TTI that are direct bolt up. No muffler shop required. The way I see it, either way, your gonna pay.
 
headers will provide more hp, the difference will be how mild or wild your engine is built...
Agree, i researched the same question and the estimates were 10-20 hp on a street engine. If IIRC a dyno test figured of headers vs the 68-71 factory 340 manifolds
Was only 8 hp difference.
 
The power difference is always in the build. Considering Jeff said “Mild build”, which leaves a lot to the imagination….
:poke:

Jeff, nothing beats the durability of exhaust manifolds.
If your considering these & are worried about a power loss, then I’d have to say seriously, don’t worry about it. You’ll notice the difference. But you did say it is a mild build, so I’ll assume the car is a drive everywhere car. Very mild cam and compression for 87 octane and Hwy gears.

Tell us about your engine build and drivetrain as well as tire size. Enquirer-I get minds wanna know!

Do you drive it all year round?
 
The power difference is always in the build. Considering Jeff said “Mild build”, which leaves a lot to the imagination….
:poke:

Jeff, nothing beats the durability of exhaust manifolds.
If your considering these & are worried about a power loss, then I’d have to say seriously, don’t worry about it. You’ll notice the difference. But you did say it is a mild build, so I’ll assume the car is a drive everywhere car. Very mild cam and compression for 87 octane and Hwy gears.

Tell us about your engine build and drivetrain as well as tire size. Enquirer-I get minds wanna know!

Do you drive it all year round?
Well, I didn't build the motor. going off what was told to me by the 3 previous owners (which none of them originally built it either) Was told It runs best on 90+ octane, has a cam of some sorts, LD340 intake with Holly 4130 dual feed carb, not a loping beast but sounds and runs good. It's a driver, NOT a drag car. 727 trans, 8.3/4 with highway gears (probably 3.23s) 15" tires. FOR SURE I don't drive it all year in Alaska :rofl:
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Well, I didn't build the motor. going off what was told to me by the 3 previous owners (which none of them originally built it either) Was told It runs best on 90+ octane, has a cam of some sorts, LD340 intake with Holly 4130 dual feed carb, not a loping beast but sounds and runs good. It's a driver, NOT a drag car. 727 trans, 8.3/4 with highway gears (probably 3.23s) 15" tires. FOR SURE I don't drive it all year in Alaska :rofl:
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nice car alaskajeff
 
For me, to help decide, knowing the cam specs and if the heads are ported go a long way. Not knowing puts things in an iffy spot. Also considering the shipping to AK and the amount of work you’ll out into it gambling that it’ll be good and OK leaves me gambling as well on the advice I’d hate to screw up on anyone.

I also hesitate to just say “Go for it!” but that just might be the case here. I personally never had an issue with exhaust manifold performance but it does fall into a certain level of performance and intended usage.

Good performance can be obtained with exhaust manifolds. It is something normally that is thought out beforehand.
 
Would these do as good as a HP OEM set of manifolds? How much HP gain or loss over headers do you think they would be? My 360 is a mild build, nothing radical. I'm wanting to put a whole new exhaust system (within a budget) in the car and just exploring options.
View attachment 1715797378
1968-74 Dodge Plymouth 340 360 318 Exhaust Manifold Pair Clean Dart Duster Demon | eBay
Those 318 manifolds are terrible...even a dead stock 2 barrel 318 responds to a set of headers. Get the early HP ones, otherwise it's a waste of time imho.
 
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