Ok, I'm getting the second engine for my CRX ready and all I need is the gasket set, but I'm not sure what head I want to run. I can choose from a Y7, Z6, or Y8. I guess the first choice would be VTEC or not. If VTEC, go with the open chamber design of the Z6 or the squared off design of the Y8. Those are my main issues. Compression ratio is of little consequence to me (using forged pistons), as is port volume (I'll be porting whichever head I use). This is a street only car that will never see more than 12psi or 7k rpm.

Theory or experience welcome

 

Right out of the box, the Y8 has the better designed head for a more effecient combustion, but if you're going to be doing any good amount of work to the heads anyways, then it really doesn't matter whether you choose Z6 or Y8 since your going to be reworking the ports/bowles/quench area etc.. which is there the Y8 holds its factory advantage.

 

You've done alot of research so you got the ideas. I beleive the Z6 head flows better than the Y8 head and can be ported easier/better. But you siad you will do the porting, so you are really down to the same question you started with.

If I had to decide I would go z6 with a gsr TB with connected MAP, for a cleaner look.

But that is me.
Randy

 

I agree with VTC.....the Y8 has the better combustion chamber........and since you are paying for the port at probably a set price go with the Y8.

 

That's what I was looking for I'll be doing the port work myself, so the cost is...well...nothing. However, I won't be really doing much to the quench area, just a little clean up, no reshaping. Oh, and I will be using a Y8 intake manifold and GSR TB on whatever head. Looks like the Y8 is "heads" above the rest If that's the case, then I'll actually be able to use the "V" in my VAFC hack

 

Hummm, very interesting. I didn't know you could bolt up a GSR TB to a Y8 manifold. Is there any changes that have to be made to it to bolt it up? Also, how big is the GSR in relation to the Y8 tb size. I know it's bigger, but how much? I want to get a new tb for my setup, but didn't want to pay big for the new ones.

 

Yea the B-series TB's bolt-up to Y8 manifolds. Stock D-series TB is 57mm, B-series are 60mm with the exception of the B18C5 which is 62mm.

 

this is something i always wondered about. i always hear something different. my '95 z6 tb is 60mm. i measured the diameter with a ruler when i took it out (inside wall to inside wall). my girlfriends '95 gsr tb is 62mm. i measured it the sameday i checked if they were interchangeable. whats up with the smaller tb's on these cars everyone else talks about?

why is the y8 intake manifold better than the z6? shorter runners?

 

out of the box, the y8 must be better in some way, because it makes 2 more HP than the z6, heh...I would assume the y8 has a slightly higher compression...correct?

 

The Y8 has higher compression due to a 32.8cc combustion chamber, as opposed to the 34.6cc Z6. Also the cam is larger (lift/duration-wise).

The Y8 manifold has larger, slightly shorter runners and a larger plenum than the other d-series offerings.

My measurements have been consitant with everyone elses (using calipers on the inner bore-manifold side)...

57-58mm for d-series (according to year and)
58-60mm for b-series (according to year)
62mm for type r

 

oh, so you measure the tb behind the throttle plate on the manifold side? that's probably what it is then. anyone try the y8 cam in a z6? wondering if this would make more power.

 

They don't like each other......