One of the reasons to use a flow bench is to get equal
flow rates in all ports. To increase flow it's just to make
holes larger but like you say, it may not make any more
power. The flow bench you describe is what it's all about.
Dont forget to flow the head with the valves installed and
one of them open to camshaft lift spec's.
Thomas
Thomas Walter wrote:
> Bill,
>
> What I wanted to point out is that "CFM does NOT equal HP".
> This kept with just the amount of air flowing into the cylinder head.
> Increasing the port size will increase the CFM (cubic feet per minute)
> of air flow, but does not always translate into better performance.
>
> So sometimes it is better to REDUCE the size of the intake port, or
> modify it so the port is not a straight shot into the cylinder, but has
> a bit of a curve to it. This will help promote the swirling and turbulence
>
> in the cylinder.
>
> A friend had a simple home made flow bench arrangement. One thing
> I that was interesting was he used a plexiglas tube over the cylinder head
>
> to simulate the cylinder. In additional to playing with the porting he
> would
> use a water bottle to spray mist into the port, so he could see the swirl
> pattern. Also with a string feed into the port had a pretty good idea
> of the turbulence induced by the cylinder head. This was over ten years
> ago, and he was dead on with his "low bucks research". Air flow meter
> was a simple fan (simple DC motor type which produces a voltage when
> spinning - while non linear, it will allow you to make back to back
> comparisons). His "vacuum source" was a couple of shop vacuum
> cleaners. Heck, it was a low cost setup, but worked nicely.
>
> Yes, the whole system needs to be balanced and tuned to a whole.
> No point in having a radical camshaft profile with stock carbs and
> exhaust system.
>
> Cheers,
>
> Tom
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