340 vs 360 confirmation

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Woodsman341

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Would I be correct in assuming that any of the stock exhaust manifolds for an early 70s 340 will flow better than the mid 70s and late 70s 360 stock manifolds? I have a chance to pick up some 72 to 73 340 manifolds dirt cheap.

Since I'm building a daily driver I'm going to ditch these awful headers. I'm not saying all headers are awful, but the ones I currently own definitely are!

Thanks again folks.
 
68-71 340 was most desireable exhaust nmanifolds .But I wouldnt pass on the dirt cheap ones you have lined up... but now you know why they are dirt cheap. :thumbsup:

and I second ditching teh headers been there done that also. The thing is on an A body the good headers cost as much as the 68-71 repop manifolds so its a either OR... if on a budget pick up your later manifolds and run em. Good luck.
 
Dartswinger70 said:
68-71 340 was most desireable exhaust nmanifolds .But I wouldnt pass on the dirt cheap ones you have lined up... but now you know why they are dirt cheap. :thumbsup:

and I second ditching teh headers been there done that also. The thing is on an A body the good headers cost as much as the 68-71 repop manifolds so its a either OR... if on a budget pick up your later manifolds and run em. Good luck.
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Yeah, same here .

I realize that any difference would be slight, but I have the option of the 72-73 340 or a set of 75-76 360 manifolds.
 
I took the headers off my 69 Cuda with a 360. They drug over every bump. I enjoyed removing them….. I used the 72-73 340 exhaust manifolds, they fit great and work great for a streeter. I doubt that you would notice any difference other than your wallet.




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Mike69cuda said:
I took the headers off my 69 Cuda with a 360. They drug over every bump. I enjoyed removing them….. I used the 72-73 340 exhaust manifolds, they fit great and work great for a streeter. I doubt that you would notice any difference other than your wallet.




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Yep! The previous owner installed the absolute cheapest headers on the market. The flange literally drags the dirt road I live on, and going in reverse is absolutely out. I went to raise the front torsion adjusters, but the center link is already hitting the lower header tube, and of course the link passes through the headers. So yeah, stock manifolds all the way.
 
68-70 were the good 340 manifolds. In 71 they became much more restrictive. I doubt the 71+ 340 manifolds flow any more or less than a 360 manifold.

Rule of thumb on A body header is if the steering linkage goes through them they will drag on bumps.
 
In my opinion, the '72 & '73 340 manifold is a 360 manifold of the same era. Later the 360 manifolds had the smog ports.
 
For a streeter, The cam and gears combo will pretty much dictate if the headers are gonna be a big deal.
IIRC the early 340 cars picked up something like 30 odd horsepower with headers, but up around 5000/5200. So if you had 3.23 gears with a TF auto, you might not get to 5000 in Second gear, until 77mph ..
But if a 4speed and 3.91s, then 5000 in Second is 53mph, now the cam wants headers, cuz 77 will be top of Third gear and flying!.
 
MoparMike1974 said:
68-70 were the good 340 manifolds. In 71 they became much more restrictive. I doubt the 71+ 340 manifolds flow any more or less than a 360 manifold.

Rule of thumb on A body header is if the steering linkage goes through them they will drag on bumps.
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The passengers side '71 340 was more restrictive lower flowing then the '68-'70 pass side. '71 drivers side flowed as much as the earlier ones.
 
AJ/FormS said:
For a streeter, The cam and gears combo will pretty much dictate if the headers are gonna be a big deal.
IIRC the early 340 cars picked up something like 30 odd horsepower with headers, but up around 5000/5200. So if you had 3.23 gears with a TF auto, you might not get to 5000 in Second gear, until 77mph ..
But if a 4speed and 3.91s, then 5000 in Second is 53mph, now the cam wants headers, cuz 77 will be top of Third gear and flying!.
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I currently have a 3.91 Sure Grip, TF904, but the previous owner was a quarter mile hole-shot driver (his description, not mine). I plan to swap the 3.91 with a 3.23 for spirited street driving at best. I'm not looking to out-race anyone, just a peppy daily driver.

Still, if I can get slightly better flow for the same money, I feel it would be dumb not to.
 
Well, damn, I fell down the rabbit hole!

After digging, it seems like the matched set 72-73 340 manifolds (and others?) Have a 2 1/4 outlet on the driver's side, 1 7/8 on the passenger side. Is there a matching 2 1/4 passenger side, or does the difference really matter?

Thanks...
 
Woodsman341 said:
Well, damn, I fell down the rabbit hole!

After digging, it seems like the matched set 72-73 340 manifolds (and others?) Have a 2 1/4 outlet on the driver's side, 1 7/8 on the passenger side. Is there a matching 2 1/4 passenger side, or does the difference really matter?

Thanks...
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My 340 manifolds are what you described. I was using a stock exhaust which necks down to about 1 3/4 or so at different places, so I decided it doesn’t matter.

If you search the forum, sone folks use jeep Cherokee passenger side manifolds the can be modified with a little grinding to be 2 1/4 as I recall. However, the outlet is is a different spot, so you will need a custom head pipe.

Does the 1 7/8 make a difference? Probably does, just depends on how much time and money you have to chase down the rabbit hole……
 
Woodsman341 said:
After digging, it seems like the matched set 72-73 340 manifolds (and others?) Have a 2 1/4 outlet on the driver's side, 1 7/8 on the passenger side. Is there a matching 2 1/4 passenger side, or does the difference really matter?

Thanks...
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Yes, this is correct. One side is a 2 1/4 flat flange and the other is smaller with a ball socket type flange. Im pretty sure this was the case on the 71's as well. If you want the big 2 1/4" opening on both sides you need to shell out ridiculous money and get some 68-70 340 manifolds.
For a mild street driver I would send the 72-3 manifolds. They flow decent
 
MoparMike1974 said:
Yes, this is correct. One side is a 2 1/4 flat flange and the other is smaller with a ball socket type flange. Im pretty sure this was the case on the 71's as well. If you want the big 2 1/4" opening on both sides you need to shell out ridiculous money and get some 68-70 340 manifolds.
For a mild street driver I would send the 72-3 manifolds. They flow decent
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I picked them up yesterday, along with a set of '75 high back bucket seats with tracks in very good condition , the stainless drip rails and wheel moldings (all in excellent condition), hood hinges, AC compressor brackets, hood bracing, an emblem or two, and a few other detail bits I was missing, all for almost nothing. Just a local Mopar guy, "friend of a friend" - now a friend after this past week - who was looking to help out instead of get rich. I'm amazed how supportive Mopar folks are of each other, in person and here.
 
AJ/FormS said:
a 360 in an A-Body was born peppy, and doesn't need much help.
A Magnum needs even less.

But if a rebuild is scheduled, the LA can easily sneak up on the Magnum.
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A rebuild is definitely on the list. I have no idea what the previous owner did or didn't do, so I'm erring on the side of caution.
 
rumblefish360 said:
In ‘74, the 360 made it into the Duster. Not what I’d call a peppy engine year for any car.
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Correct it was a dog
still prolly better then what then other 1974 offerings except the sd455 trans am 13.9@104 i question that mph with 8 to 1 comp t400 and 3.42s thats a higher trap then older lighter cars non smog engines
 
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