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I have just finished reading this article about David Vizard's PolyQuad 4 valve Head design. (all 4 valves different sizes to promote Swirl).

http://www.motortecmagazine.net/the-future-of-4-valve-engines/


You will have to Google it, I don't have enough post to add links...

What are your thoughts on doing this to a D16a6 N/A ? By Using one oversize intake and one oversize exhaust valve...
 

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MuthaFuckaUppa
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Colt Cams has their Tri-Flow cams that help promote swirl. I have thought about how this could be improved upon by using different sized valves. I wouldn't think that the exhaust valves would help much, but then again if you drain a bottle it empties faster if you swirl it.
 

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Meat Popsicle
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Have heard nothing but good things about those colt tri flow cams but damn they’re a little pricey at almost $400.

I wouldn’t spend a ton on head work. It’s an old head so it’s gonna need some maintenance work. New guides and seals, a good valve job, some quality aftermarket springs, and OEM retainers. You can do a mild port job yourself.

There’s honestly not a ton to be gained with oversized valves and a fancy port job. You’ll be much better off spending that money on a good cam.
 

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Meat Popsicle
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I did the .5mm oversized valve thing on the head that Endyn built for me.

I wonder how much of a difference (if any) that it really made since the valve seats are the same size.
 

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MuthaFuckaUppa
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Larger valves with a stock valve seat will not improve flow, it probably made less flow. Covering a hole with a bigger lid.
 

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My 2 cents is that the early heads utilized a tumble rather than a swirl and that later y7 and y8 heads that utilize swirl theory and quench pads will see benefit from this that exceeds doing it on a tumble type head.

The intakes differ on the swirl vs tumble heads because promoting velocity is important to promoting swirl. A polyquad head with a cam that accentuated the flow disparities that create swirl will be at its best with a y8 intake and port work that maintains the ratio between the runners. (So dont hog both out like ur tryna make power on a z6 or a6)

That said i think while promoting swirl can make very good power its proven the big port z6/a6 setup utilizing tumble flows more and can make more peak power.
 

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MuthaFuckaUppa
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I would say your partially correct, there are 3-valve and 2-valve d-series for swirl before the y7 and y8.


I think one of the newer hybrids civics uses a 2-valve head.

I wish Honda would revisit CVCC, maybe with direct injection.
 
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