36 to no finer than 60 grit is just fine.
You will be hard pressed to build a 200 cu in plenum...
10 X 5 X 4 =200 and will not reach the end runners very well.
----- Original Message -----
From: "Larry Mayfield" <drmayf@mayfco.com>
To: <land-speed@autox.team.net>
Sent: Sunday, June 05, 2011 11:48 AM
Subject: [Land-speed] Intake Manifold Question(s)
> Ok, those of you who consider me a crank can hit delete now, lol....
>
> I am making or revising an old manifold for use on the Sunbeam. I notice
> that the runners are pretty dog gone rough and I want to do port
> matching and polishing. My questions have to do with the smoothness of
> the air flow in the runners. This is an EFI manifold so it is what I
> would call dry. No fuel in the manifold. So do I want a really smooth
> runner wall or rough? If smooth just how smooth? Should I have it
> extrude honed for smoothness and removal of any small turbulence
> generators? If really smooth would coating the runner walls with glyptol
> be a good thing? That stuff drys to a hard finish and is pretty slippery
> and dang near impervious to oils and anything else.
>
> The manifold will be a short runner box with a plenum about 2/3 size of
> the engine displacement (an old rule of thumb I once heard and maybe be
> invalid) for use with my HP72 turbo(s).
>
> Thoughts, comments, ideas? I'll listen to them all....
>
> Just going to try and increase the Sunbeams speed over the old first
> Sunbeam top speed. Class record speeds are way beyond my capabilities
> and pockets, lol...
>
> --
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