head flow dohc zc vs sohc zc

[eg4]

which is the better head?

[greasemonky50]

here comes a mild argument.


to my guess i would think the sohc zc flows better. but thats with out the facts just my opinion.

[christopher_davis]

It would be neat someday to take every D head and bench flow it and post up all sorts of numbers. Imagine the rep you would get lol

[transzex]

ported or unported?

Ported A6 head makes stock DOHC VTEC B's cry in shame.

[eg4]

ported, I dont meen b-series. I mean the DOHC ZC D16

[christopher_davis]

Trust me he knows he was just saying how bad ass that the a6 is

[cxserver]

stock dohc zc head vs stock d16a6 head doesnt the dohc zc flow better ?

qoute from jilcrx form zcr.com
Larry Widmer at Endyn has done considerable work and testing on the ZC over the years - this is what he has to say for NA ZC engines:

"The ports are generous, both sides. I'd never use larger valves due to shrouding. I'd configure the valve seats to curtail flow at low valve lifts, so there won't be as much reversion and backwards flow at overlap. The primary pipes on the header need to be swedged larger and maintain their round shape at the flange intersect (so there will be a gross mismatch at the top and bottom). The head should have the "quench" area welded up on the intake side, so it'll be flat with the deck, or take the easy way and mill the "quench" to the same depth in each chamber, and install pistons which have a raised "quench" on the intake side. The deck clearance on the intake side should be + .20", that's .020" out of the hole. The head should have the bowls blended to the seats, and any dingleberries removed. Do not polish or clean up the port in any way, the cross section and volumes are far too large stock. The only reason these engines aren't totally useless for the street is the short rod length and resultant high piston speed. The higher the piston speed, the higher the over all pressure drop across the valve and since this will increase velocities, the engine will think the ports are smaller, and you'll have "some" torque. The engine should also get a .5mm over bore to aid breathing. The crank is a good piece and should be made "aerodynamic"....not knife-edged."

making the ports bigger reduces the intake velocity

if you are building the engine to be boosted you don't do the same things as if it is NA - i.e. different camshafts are needed for the 2 different engines
__________________
ZCspeed Racing
www.ZCspeed.com

[Dweezil]

stock dohc zc head vs stock d16a6 head doesnt the dohc zc flow better ?

qoute from jilcrx form zcr.com
Larry Widmer at Endyn has done considerable work and testing on the ZC over the years - this is what he has to say for NA ZC engines:

"The ports are generous, both sides. I'd never use larger valves due to shrouding. I'd configure the valve seats to curtail flow at low valve lifts, so there won't be as much reversion and backwards flow at overlap. The primary pipes on the header need to be swedged larger and maintain their round shape at the flange intersect (so there will be a gross mismatch at the top and bottom). The head should have the "quench" area welded up on the intake side, so it'll be flat with the deck, or take the easy way and mill the "quench" to the same depth in each chamber, and install pistons which have a raised "quench" on the intake side. The deck clearance on the intake side should be + .20", that's .020" out of the hole. The head should have the bowls blended to the seats, and any dingleberries removed. Do not polish or clean up the port in any way, the cross section and volumes are far too large stock. The only reason these engines aren't totally useless for the street is the short rod length and resultant high piston speed. The higher the piston speed, the higher the over all pressure drop across the valve and since this will increase velocities, the engine will think the ports are smaller, and you'll have "some" torque. The engine should also get a .5mm over bore to aid breathing. The crank is a good piece and should be made "aerodynamic"....not knife-edged."

making the ports bigger reduces the intake velocity

if you are building the engine to be boosted you don't do the same things as if it is NA - i.e. different camshafts are needed for the 2 different engines
__________________
ZCspeed Racing
www.ZCspeed.com


Besides the obvious size increase, is that the reason the D15 no-tec's respond so well to the A6 cam swap? I know the castings are the same as the A6 head, but is this why they make nearly the same power stock vs. stock?

[transzex]

D15's are choked compared to the A6. Give D15's A6 cam and intake, hp will be the same but D16 will have better lowend torque.

Like the 327 vs 350 vs. 400 Chevy debate......

for comparison

D16 = 400
D15 = 350
Bisi D15 race motor = 327/302

go look up the RS ratio and you'll see exactly what I'm talking about :)

Once you make it simple, it really is simple.

[88cr-rex]

Compared to 99% of pre-1997 v8s, the a6 is really good.

Mine stock went ~180I/~125E at max lift (somewhere around .500")

The intake is excellent from the factory but you can make serious gains on the exhaust. Mine ported went 226I/195E at static (again guessing .500")

The micrometer attached to our flowbench was broken, awaiting a new superflow bench . . . :D

[Dweezil]

D15's are choked compared to the A6. Give D15's A6 cam and intake, hp will be the same but D16 will have better lowend torque.

That much is easy to figure out, but I'm just wondering if the port size come into play the same way.

Like the 327 vs 350 vs. 400 Chevy debate......

for comparison

D16 = 400
D15 = 350
Bisi D15 race motor = 327/302

go look up the RS ratio and you'll see exactly what I'm talking about :)

Once you make it simple, it really is simple.

But what about the 350 Chevy made from a 400 block and 302/327 crank....

Not from the factory, but the good ones never are

[transzex]

your still stuck with the shitty 400 crank and super shitty block.

[Dweezil]

your still stuck with the shitty 400 crank and super shitty block.

Ummm...302/327 crank, 400 block dosen't involve the 400 crank.... What's wrong with the 400 block except the (sometimes) oddball #5 cam bearing?

[shoebox_civic]

how about an EJ257 crank in an EJ22T with ported v7 heads?

[C.S.A. Civic]

So the dohc zc head flows the best also doesnt it allow bigger cams to be used as well as better tuning option when it comes to cam gears