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()*#$(*$
93 Legend L Coupe.
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Discussion Starter · #1 ·
I originally purchased a Y7 head back in 2003 with the intention of using it to build a high compression SOHC engine. When I bought it, I was under the impression that this head is bascially just like the Z6 head, but without the VTEC.

However, talking with Mista Bone, who always likes to throw a monkey wrench into my plans, says that the A6 head is better from a flow standpoint. However, what research I have done points to the Z6 head being better designed to flow better. Mista Bone contends that the A6 head, with it's smaller valves and less-shrouded combustion chamber, will ultimately make better power than a Z6-type head.

Also, to make the same compression, I would have to mill the A6 head down, which is another expense I hadn't planned on having. I would also like to know how much milling it would take to achieve comparable compression ratios.

So, is the Y7 head casting like the Z6 in terms of the ports? Does anyone have an opinion on this? Thanks.
 

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On what engine you'll be puting that Y7 head?
 

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88 ED6
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5,511 Posts
overbore with the y7 head :)

I was going to get a Y7 head last weekend to replace the Z6, but went to the gunshow and bought some accessories for my SKS instead.
 

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()*#$(*$
93 Legend L Coupe.
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11,404 Posts
Discussion Starter · #9 ·
I already have P29s for my build. I was looking for ~12:1 compression. The Y7 head would get me there without any milling. I've decided to stick with the A6 head just for the cam choices, and will eventually mill the head to suit whatever compression I want to end up with.
 

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I'll upload the pictures later (if I find my USB cable), but this is what I got...

I measured it horizontally <----------> on the intake side:

a6 head = roughly 40.7mm

Y8 head = roughly 42.1mm

y7 head = still has an intake manifold on it and I don't feel like pulling it off, I might do it later this evening.
 

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Curious George
'99 LX Civic Sedan
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A6 head has both intake and exhaust 1mm smaller valves.

You can port intake and match it to similar size z6 port. I made it, and fit very well to y8 gasket.
 

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93 Legend L Coupe.
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11,404 Posts
Discussion Starter · #15 ·
I think that I am going to run the A6 head first then work on the Y7 head and see if I can get it to perform as well or better. Using a stock-ish PM3 casting will also give me more tuning room, since I have never run that high compression before. It will give me a chance to learn more about what is going on before going to the extreme right away.

As far as having smaller valves, Mista Bone informed me that Bisi didn't go to larger valves with his non-VTEC head until he bored the engine out to 78mm. I'll eventually post up what is going on with the build, but right now, I have to go to Louisiana for pre-deployment training. I'll be back at the end of Aprand after that, I don't know how much time I'll have to get ready to swap the engine in, because I'll be going to Iraq. Blech.
 
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