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...musical exhaust manifolds...

1627 Views 45 Replies 15 Participants Last post by  Canadian country boy
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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's do flow better than any of the truck manifolds for sure but so do the Magnum manifolds. Actually the best manifold combo is the drivers side 340 manifold and the passenger side Magnum manifold. The 340 manifolds on both sides exit in between cyl#'s 5 and 7 and 6 and 8, so they are in between the Magnum manifolds and the 318/360 manifolds. Why not just get some shorty block hugger headers from Summit?


Or you could go with the Magnum manifolds and run a Lokar cable kickdown....

If the truck manifolds flow equally to the 340 manifolds, would it make sense to use the truck ones and sell the 340's for $$? I imagine they have way more value than the truck manifolds. Just my 2 cents......
They don't. Only the Magnum manifolds flow close to the 340 manifolds but only the '68-'70 340 manifolds. The '71 and later had a small exhaust port on the passenger side.
92/93 360 manifold- 2 1/8" exit hole
96/97/98 Jeep Grand Cherokee 360 manifold - 2 1/8" exit hole
Stock 318 manifold - 1 5/8" exit hole
70s 340 passenger manifold - 1 7/8" exit hole
All 340 driver's manifolds - 2 1/4"
60s 340 passenger - 2 1/4" exit hole

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Shorty headers flow better than 340 manifolds for torque and horsepower by only 10 ft lbs and horsepower which can be hard to notice sometimes.
I thought you were going with 340 manifolds?!? Those aren't center dump or rear dump, they are in between.....
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Here are the 340 manifolds.....

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Don't tell me to "keep up", bro.
Pay attention. ;D
Yes well, apparently so 'eh! I hate being called bro.
I know Sam has a bit of a disliking towards me for my free thinking and when I hear that kind of tone I take it as a bit cheeky, but im a big boy, I'll be alright. 馃槈
The Grand Wagoner had a 30 year production run. It ranks 15th in the longest produced vehicle of all time. Not a bad run. 馃憤. I'd rock a Grand Wagoner all day long. Cool rigs.
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