72' 340 Drivers side HP manifold vs older HP manifold

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4mulas

4mulas

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I have a chance to buy a 72 casting number LH hp exhaust manifold and a 70 RH HP exhaust manifold,

Question. Is there a performance difference of the LH 72 manifold versus and older casting number LH manifold, say 69 or 70?

Also, What are they worth$$ ??

I have headers now and am also wondering if there is a significant difference of performance between the headers and the the two hp manifolds in question. My motor is a mild built 340.

The LH manifold casting number is 3614368-1. Dated 3.27.72
The RH manifold casting number is 2863549 no date maybe there is a L2 also cast into it.

Thank you so much!!
 
There's an improvement over manifolds with headers, yes.
 
Are they worth getting, just to have, No. Are they worth getting because you want or need them and are going to use them, Yes. will they perform as well as headers, No. How much of a difference-headers vs manifold, you can feel it, but actual Hp & Tq numbers I don't know-enough that I couldn't bother to look it up. New Manifold vs old manifold, I can't imagine enough of a difference to make it worthwhile BUT maybe I'm wrong. If one was going for a correct looking restoration or looking to race in F.A.S.T. it might be worth looking into.
I once thought I was wrong, but, I was mistaken.
 
Performance of the early 340 divers side vs the later 340 drivers side is gonna be identical. As far as looks are concerned, the early ones look a bit cleaner.

And yes headers make more power at the cost of noise, ease of maintenance etc., depending on make and model of course.
 
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In the picture (above) you can see a hump on the downward sweep of the late 340 (background) while the early 340 is virtually flat.




In the next 2 pic you can easily see that the early 340 is taller with respect to the exhaust ports:

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In this last pic you can see that the early 340 rises higher (vertically) than the late 340:

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Doesn't it depend on RPM??? From what I have read and experienced headers are great for performance at the higher RPMs (5500 and up). But at the lower RPMs a good set of 340 manifolds don't really hurt your engine performance more than 3-4 percent. As far as the difference in the early 340 VS the newer....they are virtually the same as far as flow is concerned. They are designed differently in that the early manifold rises higher in relation to the exhaust ports. The early manifold also seems to "hug" the engine a little tighter, for these reasons the early manifolds fit better on the early As than the older 340 manifolds. Unfortunately the early manifolds are usually more expensive and harder to find because there were very few made.
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Treblig
 
Treblig said:
View attachment 1714947141


In the picture (above) you can see a hump on the downward sweep of the late 340 (background) while the early 340 is virtually flat.




In the next 2 pic you can easily see that the early 340 is taller with respect to the exhaust ports:

View attachment 1714947142 View attachment 1714947143


In this last pic you can see that the early 340 rises higher (vertically) than the late 340:

View attachment 1714947144


Doesn't it depend on RPM??? From what I have read and experienced headers are great for performance at the higher RPMs (5500 and up). But at the lower RPMs a good set of 340 manifolds don't really hurt your engine performance more than 3-4 percent. As far as the difference in the early 340 VS the newer....they are virtually the same as far as flow is concerned. They are designed differently in that the early manifold rises higher in relation to the exhaust ports. The early manifold also seems to "hug" the engine a little tighter, for these reasons the early manifolds fit better on the early As than the older 340 manifolds. Unfortunately the early manifolds are usually more expensive and harder to find because there were very few made.View attachment 1714947141 View attachment 1714947142 View attachment 1714947143 View attachment 1714947144

Treblig
Click to expand...
Thanks for the great reply treblig. I'm generally not a fan of headers for all the reasons you mentioned which is why I'm asking all these questions to begin with. So what I'm hearing is that manifolds for the most part are going to perform we'll with the the exception of perhaps higher rpm use which all be it fun, is not the range we mostly drive in anyway.
Did you mean to say that the early manifolds hug and fit better that the later manifolds? If you re read that section it says early fits better than 'older'?

I'm contemplating these so I can put on normal exhaust and also get the ride height back to more of a normal stance on the car. I just got the car and this is how the previous owner had it all set up.

Thanks so much!

image.jpeg
 
What I wrote was very specific...."for these reasons the early manifolds fit better on the early As than the older 340 manifolds." I specifically wrote that the early 340 manifolds fit better on the "Early As", which has nothing to do with your car. By the way, very nice car!! Either manifold will fit your car, the major difference would be in price and availability. The early 340 manifolds seem to cost more on average. The early manifolds are slimmer so they give early A owners a little more clearance around the steering box and steering shaft but in a '72 it makes no difference at all. In fact I would prefer the newer 340 because it beefier and less likely to crack/break. The later 340 also comes with those raised ears/ribs which give you a place to attach a plug wire shield. I have a later 340 on my '69 Barracuda and it fits perfect.

Treblig
 
Treblig said:
What I wrote was very specific...."for these reasons the early manifolds fit better on the early As than the older 340 manifolds." I specifically wrote that the early 340 manifolds fit better on the "Early As", which has nothing to do with your car. By the way, very nice car!! Either manifold will fit your car, the major difference would be in price and availability. The early 340 manifolds seem to cost more on average. The early manifolds are slimmer so they give early A owners a little more clearance around the steering box and steering shaft but in a '72 it makes no difference at all. In fact I would prefer the newer 340 because it beefier and less likely to crack/break. The later 340 also comes with those raised ears/ribs which give you a place to attach a plug wire shield. I have a later 340 on my '69 Barracuda and it fits perfect.

Treblig
Click to expand...
Ahhhh, I got you now! Early A being 66 and prior. Wasn't really reading that right! Thanks for clearing that up, and good point about the beefier casting comments on the 72 manifold that I'm contemplating.

BTW... You mention price and availability. What would you deem reasonable for a pair of these manifolds then (LH 72 and right hand earlier). Also I guess I would need a heat shield for the drivers side, anything else etc..?

Thanks!
 
Well.....it just so happens that I sell these manifolds. That's not why I chimed in, I was simply trying to help you out. To answer your question, a good set of original 340 manifolds (L & R) go for $450/$500 to $850 depending on who you buy them from. If you have a close friend you can maybe get them cheaper?? Finding a good set for $450 might take a while?? I've sold at least 30 pair of my manifolds to many FABO members. But to save everyone money I developed a method to take a 360 magnum (passenger) manifold and machine it out to the same size as a 340 driver. The 360 (passenger) magnum cost less and doesn't break like the old (50 year old) manifolds. I search all over the US for 340 driver and 360 magnum manifolds, buy them, machine the 360 magnum, sand blast paint, primer and top coat with high heat paint and sell them as a "pair". I also make the 120 degree down pipe for the 340 driver to clear the torsion bar.


As you can see in this first pic the 360 magnum can be machined out to a little over 2 1/4" which makes the exit hole the same size as the 340 manifolds"


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Here's a pic showing the difference between a 360 magnum and a 318 manifold....believe me there's a big difference. They didn't use the 2 1/4" exhaust hole on the 340 6 pack engine because it "looked good"!!

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treblig
 
4mulas said:
Thanks for the great reply treblig. I'm generally not a fan of headers for all the reasons you mentioned which is why I'm asking all these questions to begin with. So what I'm hearing is that manifolds for the most part are going to perform we'll with the the exception of perhaps higher rpm use which all be it fun, is not the range we mostly drive in anyway.
Did you mean to say that the early manifolds hug and fit better that the later manifolds? If you re read that section it says early fits better than 'older'?

I'm contemplating these so I can put on normal exhaust and also get the ride height back to more of a normal stance on the car. I just got the car and this is how the previous owner had it all set up.

Thanks so much!

View attachment 1714947151
Click to expand...


if i were going to put manifolds back on that car i'd put the correct ones for it on. i think it would just look better with the correct ones on it.
 
I agree if you're trying to get the car back to stock. If the rest of your car is all stock then it would be best to use original (by year) manifolds. You said you had a line on a set of manifolds but you didn't say how much they were selling for. If you're not trying to get your car back to how it came from the factory I wouldn't spend too much money on the "correct year" manifolds unless you can get them for a good price.

treblig
 
There are more than a few tests on lower HP engines where headers outperformed manifolds by 10+ hp and 20#'s of tq at 3500 rpm.
 
Treblig said:
I agree if you're trying to get the car back to stock. If the rest of your car is all stock then it would be best to use original (by year) manifolds. You said you had a line on a set of manifolds but you didn't say how much they were selling for. If you're not trying to get your car back to how it came from the factory I wouldn't spend too much money on the "correct year" manifolds unless you can get them for a good price.

treblig
Click to expand...
I do have a line on them And will probably get them. If you had an earlier drivers for the 69 I could do a swap with the the later 72 one I'm contemplating?? I can post photos of each but need to use my phone instead of the tablet I'm on. I can do that in a bit.
 
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