best non vtec sohc d series head

[EvoTec1]

im trying to make a ringer d15 for our shop that we can say is all stock factory parts... dont ask.

So are there any differences in head design from one generation civic to the next? Is there any advantage in using a newer head?

We've heard (heresay) that newer heads are more efficient, as they make similar hp numbers as the older motors, with a smaller cam. Is this simply compression making the difference, or is the head actually better flowing?

 

[civicious]

There's not really a whole lotta difference in the 16-valve SOHC non-vtec heads - the difference is in the camshaft (and I believe the D16A6 has the most aggressive camshaft from the factory).

I'm using a head from a '92 D15 SOHC non-vtec on my drag crx, but it's been ported and reworked quite a bit.

 

[EvoTec1]

yeah, kind of looks like what were tryingto do... what do you run?

 

[INJEN78]

+1 for the a6 head...

 

[EvoTec1]

A6 is what im looking for then.... anyone else got the A6's back on this one?

Ive heard they have smaller valves.... this is made up for in port flow?

I will be hogging these things out considerably....

 

[K2e2vin]

Z6 head with Y7 rockers.

 

[get_nick]

what shop are you doing this for?

 

[EvoTec1]

we have a friend thats going to work with them, but actually "hogging out" was a bad term to use, since HC rules dictate that only the first inch of the port can actually have work done....

Believe me, blanco, im hip to the velocity tip... there are dumbas ses driving chevys that think 4" duals and big heads are the WAY to go if you want power. Velocity is the thinking mans choice regardless of engine configuration.

SPEAKING of which...

Anyone know where i can start learning about port wall finishes? I hear that roughened surfaces designed to create a turbulent boundary layer will improve velocity and flow over a polished smooth surface, but our guy doesnt have that type experience...

The shop is ttp out of fredrickson... It's really just a buch of guys that want to race. This summer we're starting to put together the car to get some strip numbers, and then next year we'll hit the roadcourses. A lot of those HC guys are competitive with stuff that isnt that exotic. If we had a d15 making decent numbers (say a 15 flat?) without vtec on a stock cam... we'd be happy.

Do y7 rockers have a different ratio? we are using a stock 91 si cam

 

[evokilla@nadsny.com]

the d16y8 has been said to have the best flowing head...but tends to lift under certain operations (mainly boost)....and there is deff a difference other then just internal parts like combustion chamber design and flow but if I had to pick I would choose the d16z6 although these are vtec heads ......non-vtec best head you can get is not a d series..it is the F22

 

[K2e2vin]

The D16Z6 has the highest flowing head(just a tad higher than the Y8). Reason is one of the ports on the Y8 is turned a little to promote swirl. What's nice about the Y8 heads are the quench pads.

The 91 Si cam won't work in a Z6 head with Y7 rockers; you'd need to use the Y7 cam or have it reground(Delta can set you up with a decent 272 or 282 regrind for like $70). If you're going to use a 91 Si cam, the D16A6 and D15B1/B2/B7 heads will work just the same.

 

[93civicracer]

Why are you trying to stay away from vtec? You can just use an all stock, all factory parts z6 swap and be much better off than anything you'll get out of that d15 nonvtec without boost/nitrous. Stock B16's (170 hp 112 tq) run 15's I believe if I'm wrong someone correct me.

 

[EvoTec1]

well we've seen crxes hit high 14's with vtec swaps and si tranny's, and no one does ANYTHING witha d15 sans vtec... Plus staying Nasa HC legal is something we're loosely keeping in mind.

im googling the rocker swap and cam specs, it makes sense the vtec head would flow better.

but really, our only hope lies in our tranny and compression... we dont really know what kind of difference the 4.9 drive is gonna make. We figure that its gonna be quick off the line (for a d15) and we're looking at like a 1900 lb weight goal... Who knows, maybe we'll have a couple kills.

we're also open to compression suggestions...

ps, i dunno about 15's... here b16 swapped civics routinely hit 15 flat while gsr swaps usually run mid 14's (pacific raceway)

 

[K2e2vin]

For compression, I've heard 13-14:1 compression is doable...on pump. I believe when Bisi had his D15, he was in the 17:1 CR range with pump.

 

[EvoTec1]

yeah us too. we were thinking 10.5-11:1... 11.5:1 is ok on 91 even with an aggressive curve?? If so it sounds like instead of worrying about the best flowing head we should be looking for the smallest chamber just to maximize compression, and then work the ports to increase flow?

Anyone care to educate me about how quench affects things?

 

[EvoTec1]

What is this? a 2001 d17a1 sohc non vtec head? made 115hp and 110 lb ft of torque on a 1.7 liter motor?

I've never heard of it! Will a head from this motor fit on a d15?

 

[K2e2vin]

Nope. D17 blocks are different than the older D-series. You can, however, use the D17 crank, rods, and pistons in a D16 block to create a stroker engine. Requires a few mods but it's been covered(search on D-series.org).

01-05 Civics had D17s instead of D16s or D15s.