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Old 07-23-2009, 01:23 AM   #1
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Default Best head setup-valves

So I am going to be doing a built engine for my MSM and looking for around 320-350whp.
It is an MSM head and I would like to have a redline of about 8K or so. I will make the proper oil pump mods.
I have a couple of questions about head modifications.
I am not going to go all out on porting but I have read that what our heads need is the valves unshrouded. Is this true in your experience?
I am probably going to go with Integral stage 2 turbo cams with supertech valve springs and retainers.
My other questions-
Are oversize valves useful at this power level? Some info suggests it would be helpful others think the valve size on our head is already pretty large.
3 angle valve job adequate?
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Old 07-23-2009, 01:50 AM   #2
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Personal opinion: Exotic headwork is not nearly as rewarding (in terms of cost:benefit) on a forced induction engine as in a naturally aspirated application. While there are certainly gains to be had in terms of efficiency, it's a rather simple affair to just crank up the boost a notch.
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Old 07-23-2009, 02:19 AM   #3
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Thats what I was thinking as well. My statements don't really hold water though, I am neither boosted, nor have I done extensive head work.
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Old 07-23-2009, 07:13 AM   #4
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Our valves are definitely large enough, oversized valves would appear to cause a larger disruption in the airflow in the space between the valves. I have OEM sized Supertechs in my '99 head (which are already backcut and undercut), the machine shop did some light port work leading up to the bowls, some deshrouding, some bowl blending, and of course, valve seating. Basically they said it was nothing extreme but would help smooth and increase the airflow.
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Old 07-23-2009, 10:35 AM   #5
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throwing in a few uprated components for the head isn't too expensive... the standard size slimmer stem valves are a good option as rotornut suggested, I stuck with those and plan to do a little DIY unshrouding (something oversize valves may not allow and then what good are the oversize valves??). I'm putting in lighter retainers and stiffer springs also.

A proper 3+ angle valve job will also help flow some and is probably a good idea for any head build.

cams would be good...

but keep in mind also, there's limitations of the stock intake manifold. Just search for Paul's dyno numbers to see his near-redline power climb. If you plan to rev, you're going to want flow above redline to improve and the miata's stock setup is notoriously saggy above 6k.
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Old 07-23-2009, 11:12 AM   #6
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Ok thanks,
as for the intake manifold I am waiting to see when BEGi releases their tubular intake mani, I talked to them and it seems they still have a couple of the cast intake manifolds as well. Otherwise something like the Flipside manifold that someone posted about might be useful.
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