Manifold question Center dump ram? - Impala Tech
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post #1 of 3 (permalink) Old 09-08-2014, 12:31 PM Thread Starter
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Manifold question Center dump ram?

I'm told the center dump ram manifolds on a SBC Motor will produce similar gains as headers. Do you feel this is a true statement? If so which manifold do i look for? Some have different size ports than others.
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post #2 of 3 (permalink) Old 09-08-2014, 02:04 PM
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One of our members dynoed his 383 and found that up to about 4,500 RPM the 2-1/2 inch "Rams Horn" cast iron manifold and a set of long tube headers made the same power. Above that RPM and the headers made more power. You want the 2-1/2 outlet manifolds found on high horse engines (rated at above 300 horsepower).

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post #3 of 3 (permalink) Old 09-09-2014, 09:56 AM
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The engine was made to appear perfectly stock from the outside, so I had to use stock 327 block, stock intake manifold, stock heads, stock exhaust manifold. Much more power could be made with newer design intake and heads. Just paint them orange, and most folks would never know But I wanted it to pass judged events.

You can see that the headers do give a slight increase over all, but nothing notable till you are over 5400 RPM. And be honest, how much time are you going to spend in that RPM range? For me it all about the easy low end torque that gets me moving quick, without breaking a sweat.

Open questions remain though. Would I see better performance with the headers if I had aftermarket (higher flowing) intake and heads? Remember the stock heads and intake I used were designed for 327 cubic inches not 383. I also wanted the engine to be well mannered enough to work with the power brakes and A/C, which meant a fairly mild cam.

This shows the difference between the "2 inch" and "2.5 inch" rams horn exhaust manifolds. There seems to be more than 1/2 an inch difference to me, but it is obvious the 2.5 inch manifolds can flow a lot more exhaust.

These are the 2.5 inch manifolds I used on my '64. Notice the slight bell shape on the manifold where it bolts up to the head pipe. That bell shape is not present on the 2 inch manifold, so you can identify them quickly this way.

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