340 Manifolds on 318

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H22A4

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After upgrading the 318 with a 4bbl last year, there was still the choke point of the 318 manifolds and 1 ¾ downpipe from the old, crush bent dual exhaust that was installed on the car a long time ago. Several years ago I had a 2.5” exhaust installed from transmission back but didn’t touch the downpipes since I knew different manifolds were going to be installed at some point.

I thought about buying both downpipes from TTI based on the casting numbers of my 340 manifolds. The passenger side is the easy one so I bought the TTI downpipe but the driver’s side downpipe is a challenge with the tight fit between the torsion bar and starter motor. One of our solution providers on FABO (Treblig) makes 120 degree 340 downpipe for the driver’s side which I bought. That eliminates the need to fit the downpipe down between the starter and torsion bar but further back past the starter instead.

Even though my 318 has ‘302’ heads, spending the big $$ on the early 340 manifolds didn’t make much sense to me so I bought a set of later 340 manifolds:
340%20manifolds_zpsxjtpwkvq.jpg


Cleaned up after sandblasting:
sandblasted_zpswmog4ahu.jpg


Painted with Eastwood High Temp manifold paint:
eastwood%20manifold%20paint_zpsno3ulp4c.jpg


Old exhaust manifolds on the car:
old%20manifold_zps5frmzfcl.jpg

old%20manifold%202_zpso35jl0s5.jpg


Old drivers side downpipe with the famous dent:
old%20downpipe_zpsdiq4ds83.jpg


Also replaced the full size starter motor with a mini starter. Last thing I wanted was for the starter motor to die down the road and not be able to replace it easily:
mini%20starter_zpsx5t2xdbc.jpg


The TTI passenger side downpipe matched up pretty well to the existing 2.5” kit:
new%20downpipe%202_zpsnoaybo6l.jpg


The rest are photos of the driver’s side using Treblig’s 120 degree 340 downpipe.
new%20downpipe_zpste3shsrh.jpg

new%20pownpipe%203_zpsfiknf2b1.jpg
new%20downpipe%204_zps68yetaoe.jpg


Top side shot of the 340 manifolds:
newmanifold_zpse7bgitgb.jpg

newmaniffold2_zpshncg4dri.jpg
 
I used the later 340 manifolds also, but my driver side was the log style. I used TTI headpipes on both sides and was impressed. You should notice a difference
 
It might only be 4 HP, maybe 5. Mopar Muscle magazine did a manifold test years back and gained 7 HP on a mild 360.
That gain would be greater with more cam,more compression and more cubic inches.
If you did this for appearances, that is another matter. :thumbsup:
 
It might only be 4 HP, maybe 5. Mopar Muscle magazine did a manifold test years back and gained 7 HP on a mild 360.
That gain would be greater with more cam,more compression and more cubic inches.
If you did this for appearances, that is another matter. :thumbsup:
Chris, another great write-up. I'll be bookmarking this. I almost have enough saved for my TTI exhaust. I've already made the recommended TTI mods to the driver's side bellcrank, so I'm hoping for no issues there. Mini starter, yes. I bought the passenger side 360 manifold and a short downpipe:thankyou: from Treblig, so I know I'll need some help hooking up that side.
 
Chris, another great write-up. I'll be bookmarking this. I almost have enough saved for my TTI exhaust. I've already made the recommended TTI mods to the driver's side bellcrank, so I'm hoping for no issues there. Mini starter, yes. I bought the passenger side 360 manifold and a short downpipe:thankyou: from Treblig, so I know I'll need some help hooking up that side.

Thanks.

Is the exhaust work the next project on your list?
 
Thanks.

Is the exhaust work the next project on your list?
Yes, I've been e-mailing Mancini about the passenger side head pipe. With the 360 manifold, I'm going to need some cutting, welding, etc. I'll keep you posted.
 
nice write up, but what car is this on? i swapped /6 out for a 360 and would like to know if any of this will work on a 66 Barracuda. Especially that driverside rear dump 340 man. i see YearOne has the 1968-1970 A-body manifolds are these the same as the ones on this thread?

Casting numbers are 2863553 (left hand) & 2863549 (right hand).
 
It’s on a 1975 Scamp. The 340 manifolds I used are the later style ones which are not the ones Year One sells. I’m not sure if this will work on a ‘66 A body.
 
i'm kinda feeling like it will work. i am intimately familiar with the under side of my car, and your pictures are very similar. the manifold look real close too. but its a big investment to just try so im doing some homework
 
nice write up, but what car is this on? i swapped /6 out for a 360 and would like to know if any of this will work on a 66 Barracuda. Especially that driverside rear dump 340 man. i see YearOne has the 1968-1970 A-body manifolds are these the same as the ones on this thread?

Casting numbers are 2863553 (left hand) & 2863549 (right hand).
The late 60s 340 driver should work in an early A. I've sold a few of the 553 manifolds to other FABO members for use in an early A, BUT!!!!!!!...you must have manual steering!!! The power steering unit does not allow enough room for the 340 driver's manifold. The other question, "Is the late 60s 340 driver's manifold the same as a 70s 340 manifold??" The answer is "NO", they have a similar design but the 70s manifold has ribs on top and bottom where the 60s has no ribs. The 60s manifold also rises higher off the exhaust ports more steeply giving you more clearance. That's why the 60s manifold will work but the 70s won't.
I've read about some folks who have used a 70s manifolds in an early A but there were modifications required. I've never seen a 70s manifold on an early A that didn't require many mods???

Treblig
 
Here are some pics I have so you can see for yourself. The ribs are very obvious on the 70s 340 manifold, you can also see the difference in "rise" height:

DSC04317.JPG
DSC04024.JPG
DSC04025.JPG
DSC04027.JPG
DSC04028.JPG


I think Mopar added the ribs (1970s) to add some rigidity (to preclude cracking) and to give you a place to attach the spark plug "metal" shield. I have no idea why they changed the flow design (but only slightly).

Treblig
 
wow man. i really appreciate the detail and time spent on this response. based on all this i can make an informed decision going forward. also, have a heads up when i finally do tackle this project.
 
Awesome information, as usual, TreblOg. LOL You always share good stuff. Power steering? Who da hell needs that in a LIGHT *** early A? A sissy maybe? LOL

Here are some pics I have so you can see for yourself. The ribs are very obvious on the 70s 340 manifold, you can also see the difference in "rise" height:

View attachment 1715129438 View attachment 1715129439 View attachment 1715129440 View attachment 1715129441 View attachment 1715129442

I think Mopar added the ribs (1970s) to add some rigidity (to preclude cracking) and to give you a place to attach the spark plug "metal" shield. I have no idea why they changed the flow design (but only slightly).

Treblig
 
Awesome information, as usual, TreblOg. LOL You always share good stuff. Power steering? Who da hell needs that in a LIGHT *** early A? A sissy maybe? LOL
I agree, the whole world is becoming sissyfied!! LOL..... Especially in an early A which even lighter than a later A body?? If you add skinnys on the front it's really easy to steer anywhere at any speed.

Treblog!!!
 
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