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Old 11-29-2017, 09:28 AM
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x-bird x-bird is offline
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Join Date: Oct 2011
Location: Penciltucky
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Spent many years in the car mag biz and did a lot of tech articles in some of the top "brand specific" shops (Kaase, butler etc.) A good friend of mine (now deceased)who handled my SD engine top end showed me a lot about flow bench testing. he was an SAE-member engineer among other things with rep. going back to the early '60s. Running the head alone and only looking at total flow numbers is not a good method when attempting to analyze or improve performance. the big three learned this in the late 60s early 70s when they put out their massive number tunnel port heads for Trans Am racing and they ran like crap until peak rpm. If you flow the top end as a system with intake and exhaust systems in place, you will get a vastly improved view of how the flow through is working. My buddy was among the first to build a bench with fixtures capable of doing this outside of the manufacturers. If you can flow your setup that way first to get a baseline, you will be better able to read what any changes do. Also keep in mind that flow velocity is more important than flow volume. he had mini pitot tubes that he could insert into the stream at various points to attain that reading. He used to emphasize to me the fact that the valve is only open for milliseconds of time, or course rpm dependant, and that getting the flow through that open window smooth and fast was the key. Of all things, a thin piece of string was one of the most important tools he used. When he'd slip that into the intake stream or head intake port stream its position in the port and movement or lack thereof told him what he needed to do to the port. If it was centered and pointed right at the valve opening and as steady as a wire, he knew all was on the money. Have fun, experimentation!
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