Nope!! 70 &'71 and up were 1 7/8". If you not going 100 original, I'd swap it for a 96/97/98 Jeep Grand Cherokee passenger's manifold.Mine is 3418623 but I don't know that it is original to the car. Outlet inside diameter is 1 7/8". Is there a correct right side 1972 manifold with the larger 2 1/4" diameter?
And the matching left side manifold is 2.25", is that correct?Nope!! 70 &'71 and up were 1 7/8". If you not going 100 original, I'd swap it for a 96/97/98 Jeep Grand Cherokee passenger's manifold.
There are no dyno numbers for the JGC manifolds (that I have seen). The JGC is 2 1/8" which is as close as you're going to get without spending lots of money. The individual port are pretty good size also. The JGC does not exit in the center like the 623. It exits a little more towards the rear where there is plenty of room/space. You can easily grind out the JGC to more than 2 1/4".And the matching left side manifold is 2.25", is that correct?
Is there any right side 2.25" manifold that exits straight down in the center like 3418623?
I think I have seen some dyno numbers with different manifolds, but I can't find them. What does the smaller outlet translate to in terms of HP or performance?
I usually go for performance over originality but that is not the case with my current project so the Jeep option is out. I might consider an earlier 340 manifold if it is similar in appearance but if the asymmetric exhaust size is what the car came with, then that is likely the way I will go.There are no dyno numbers for the JGC manifolds (that I have seen). The JGC is 2 1/8" which is as close as you're going to get without spending lots of money. The individual port are pretty good size also. The JGC does not exit in the center like the 623. It exits a little more towards the rear where there is plenty of room/space. You can easily grind out the JGC to more than 2 1/4".
The driver side is 3614368.What number is on the drivers side #553?
72-74 340 -360 drivers side manifold. KimThe driver side is 3614368.
They're hard to give away because of shipping costs.....I have one hanging outside, it's used as a counterweight!!Don't pay 340 prices for the 3418623 manifold. C bodies used that manifold from 71-73 on the 360's. Fairly plentiful.
And the matching left side manifold is 2.25", is that correct?
Is there any right side 2.25" manifold that exits straight down in the center like 3418623?
I think I have seen some dyno numbers with different manifolds, but I can't find them. What does the smaller outlet translate to in terms of HP or performance?
Why didn't the factory do it like this with no dents and 2 1/4 pipe???:71-73 left side manifold had a 2.25 inch outlet, right side 1 7/8 outlet. But the pipes on both sides were only 1 7/8 (or 2 inch?) for the first couple of feet, then fed into 2.25 inch pipes. Not only that, but the driver's side pipe was indented for torsion bar clearance.
View attachment 1715684325
As for performance, I'm surprised someone hasn't posted the Mopar Muscle (I think) dyno testing of a 300 hp crate Magnum engine with different exhaust. According to them, the best 340 exhaust manifolds were only marginally better than LA 318 manifolds, and headers were only maybe ten hp better.
To that I would just cite my own experience: Back in the late seventies, I put a set of cheapie headers on my 73 Duster 340 that was stock except for a 71 intake and a 650 spreadbore Holley plus the factory heat riser was removed from the stock passenger side manifold. I didn't replace the rest of the exhaust system, which was completely factory original down to the original mufflers. The headers were worth seven tenths of a second in the quarter. Actually they were worth more, but now it had so much more low end torque that now I had a traction problem that I had not had before. Shifted at 5200 with the stock manifolds (and there was no point in going any further), shifted at 5800 with headers.
I had similar results more recently when I replaced the 68-70 340 hi-po manifolds with TTI headers in my 67 360 Barracuda with a slightly hotter than stock cam, Edelbrock RPM intake and 750 Holley, plus in this case I also replaced the 2.25 inch muffler shop exhaust with TTI 2.5 inch mandrel bent X pipe. Again, a huge gain in low and mid range, plus significantly more top end. So much more power down low that I couldn't give it full throttle in low gear without going sideways until I started running drag radials on the street.
I doubt that replacing the OEM 72 passenger side manifold with the early hi-po 340 manifold would really make much difference. At least, it didn't on my 65 Barracuda when I made that switch.
My two cents. Your experience may differ.
What size longtubes did you run, 1 5/8 primaries?71-73 left side manifold had a 2.25 inch outlet, right side 1 7/8 outlet. But the pipes on both sides were only 1 7/8 (or 2 inch?) for the first couple of feet, then fed into 2.25 inch pipes. Not only that, but the driver's side pipe was indented for torsion bar clearance.
View attachment 1715684325
As for performance, I'm surprised someone hasn't posted the Mopar Muscle (I think) dyno testing of a 300 hp crate Magnum engine with different exhaust. According to them, the best 340 exhaust manifolds were only marginally better than LA 318 manifolds, and headers were only maybe ten hp better.
To that I would just cite my own experience: Back in the late seventies, I put a set of cheapie headers on my 73 Duster 340 that was stock except for a 71 intake and a 650 spreadbore Holley plus the factory heat riser was removed from the stock passenger side manifold. I didn't replace the rest of the exhaust system, which was completely factory original down to the original mufflers. The headers were worth seven tenths of a second in the quarter. Actually they were worth more, but now it had so much more low end torque that now I had a traction problem that I had not had before.
What size longtubes did you run, 1 5/8 primaries?
I was considering getting the hi po manifolds for my 72 318 till I read this just to confirm the passenger side exit was the same as my 318 lol. Thanks for the info guys.
The "bell" is larger on the 360/340 PS exhaust manifold, otherwise it comes out the same. I had an exhaust shop modify my Commando exhaust so I could use it with the 72 340 PS manifold. I'd run the your 318 manifolds. We put 72 340 manifolds on our 73 Dart, 318. Not much difference if you are running a decent set of dual exhaust and a relatively mild cam and 4 barrel carb.
Aren't the ports larger on the 340 exhaust manifolds? Could be a problem sealing against the smaller ports of a 318 head. I think the 340 manifold's passages are larger, too. But I agree, in any event very little if any difference on a mild 318. Not worth swapping.
Aren't the ports larger on the 340 exhaust manifolds? Could be a problem sealing against the smaller ports of a 318 head. I think the 340 manifold's passages are larger, too. But I agree, in any event very little if any difference on a mild 318. Not worth swapping.