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...musical exhaust manifolds...

1629 Views 45 Replies 15 Participants Last post by  Canadian country boy
Ok folks - for my mild 360 magnum 'truck' engine...I'm looking at two versions of center dump small block manifolds (for both sides of my engine), and I've narrowed it down to these two: '71 340 p-side, and the later 70's 318/360 truck manifolds.

Both manifolds have similar port sizes, and the same 1-7/8" i.d. exhaust outlet diameter. I was going to use the magnum manifolds that were on the engine, but they aim way way back and frankly make 'getting in there' to access the transmission linkage and such pretty difficult, plus making things pretty toasty and requiring more shields, etc. The magnum manifolds also have the same outlet size of 1-7/8", and with that in mind I'm looking at center dump exhaust manifolds, so back to the 340 or later 318/360 units. The 340's flow good, and I think the 318/360 units probably flow the same, so I doubt there's not much of a flow difference that I would ever notice, and I don't care about gaining/losing 5 hp at 5000 rpm. The later units have more 'cooling fins' and a bigger internal core...but I don't know if that has any bearing.

My brain tells me these (below) both flow about the same, and will flow plenty well enough for my mild 360, again built to be 'done' by 4500 rpm - I'll just be adding gears - not for high rpms - for low rpm grunt work.

So, that said, am I missing something, or would either of these suit me just fine - I'm leaning towards the 340 units...and unless someone convinces me otherwise I'll be picking up a set of the 340 manifolds from a local club buddy tomorrow morning. But if the later truck units would be better...well tell me why.

71 340 -

70's pre-smog small block (318 and 360 I think) -

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The 340 was Chrysler's small block performance oriented engine. So it would be logical to believe that the factory manifolds flowed pretty good for their time. The magnum manifolds are pretty good too, but lack your central dump requirement. I would avoid standard LA exhaust manifolds.

I didn't recall Jeep switching to Mopar V8s when they were under the same umbrella. In fact after the Jeep/AMC 360 disappeared I figured everything got stuck with the H.O. 4.0 I6. I was aware of V8 availability just never paid much attention to what V8 was used.

I think the only reason why the AMC 360 V8 continued after Chrysler's purchase was the Wagoneer still sold very well and I think they were probably surprised by that. So what do you do with a product based on an old platform, that you intend to end, but are making a profit from? You extend it until sales dry up. Funny thing was, the Wagoneer was very popular to the bitter end

Jeep's other products at the time didn't come with V8s. The next Jeep which was intended to replace the Wagoneer, and receive a V8 would be the Grand Cherokee. The GC was under development under AMC, but it wouldn't go into production until a few years after Chrysler purchased Jeep. Since the AMC V8 was technically done, the only V8 option had to be Chrysler engines.

Apparently, theres still a market for them. The value of used models are starting to exceed their as new price. Low mileage models are in high demand and I believe theres a business or two which rebuilds Wagoneers. I think thats one of the reasons why Chrysler has decided to reintroduce an all new full size Grand Wagoneer.

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