Well I started taking apart my sohc ZC today and here are the results I have so far.

First off...proof.


Valve cover removed, looks the same so far...


Next I removed the head bolts and bolts holding down everything and removed the cam. My friend just purchased a very nice digital micrometer which he generously lent me, and that in hand I started measuring every inch of the head.

After the head removal (I think we've seen this much before) PM 6 pistons. Same as the A6


ZC head stamp PM3-2


A6 head stamp PM9-3


ZC cam on top A6 on bottom


Now for the measurements....

<U>ZC</U>
Cam lobe (when resting on the gear counting top to bottom)
1- 1.45"
2- 1.44"
3- 1.45"
4- 1.45"
5- 1.45"
6- 1.45"

Exhaust Valve - 1.01"
Intake Valve - 1.6"
Combustion chamber 2.9" diameter

<U>A6</U>
1- 1.44"
2- 1.45"
3- 1.45"
4- 1.44"
5- 1.44"
6- 1.45"

Exhaust Valve - 1.10"
Intake Valve - 1.58"
Combustion chamber 2.9" diameter

The measurements might be off by a tad...but I account that to me not being 100% accurate in the measuring. I do feel confident that they are close enough to call identical though.

I also did a simple volumetric test. I used a crude but well marked cup, leveled off the heads (I have pics if anyone really wants them) and starting filling.

Both combustion chambers took 2 cups and looked like this.

ZC combustion chamber


A6 combustion chamber


They looked exactly the same to me, or off by an nondescript amount. The picture on top looks a little less full, but that is just due to the proximity of the camera ....if you look at them with the naked eye they are identical.

I also have pictures of the comparison of the intake and exhaust ports and the valves. They are exactly the same so I didn't bother uploading them to we-todd (thanks for the hosting! )

Unless there is a difference in the stroke, or the crankshaft, or something else in the block these engines seem to be exactly the same.

Anyone who wants to come over and take the measurements for themselves are welcome if you are in the s.e. Wi. area.

I will be taking apart the block sometime this week (wed I think) so we will have full results then. As I remember the argument was that the head held the secrets to the power of the ZC. So far there is nothing secret about it.

-Jake

Edit: could the difference were searching for be in the ECU? Does anyone know what the JDM ECU is for the sohc ZC?


Modified by Superhatch at 5:28 PM 7/19/2004

 

 

obviously, the tiny secret is in the cam!

 

And the holy man hath said - be thy the same!

 

sorry to kinda jack this thread but can you bolt any A6/Z6/Y8 heads to a SOHC ZC block? I was thinking of getting one and i wasent sure

 

yes u could i have a friend that bent the valves on his DOHC ZC but didnt do any block damage so he just went straped a Z6 head on the DOHC ZC block

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 88fgfd &raquo;</TD></TR><TR><TD CLASS="quote">yes u could i have a friend that bent the valves on his DOHC ZC but didnt do any block damage so he just went straped a Z6 head on the DOHC ZC block</TD></TR></TABLE>

No, he didn't. I'm sorry but ur mistaken. SOHC heads will NOT fit on the DOHC blocks or Visa Versa.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ceLtic &raquo;</TD></TR><TR><TD CLASS="quote">obviously, the tiny secret is in the cam! </TD></TR></TABLE>

Are you serious?

He has all the cam measurements up there.... or did you not bother to read?

 

Also, could the difference just be that honda has underated the A6's power output all along? I've seen many dynos of stock A6's dyno at around 105-110 HP. If you calculate the powertrain loss on an A6, 108 HP X 20% = 22 HP. That means that going by that formula, A6's should put down about 86-88 HP to the wheels....and I've never seen one dyno that low.
I mean, crx/civic si's have always felt ALOT faster than they are actually supposed to be.....doesn anyone else agree with what I'm saying?

 

obviousley both motors are a waste of time

 

hmm that is cool I learned somthing there good post!

 

The truth shall set you free!

Good to get some proof 130hp sohc zc my ***!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sporkcrx &raquo;</TD></TR><TR><TD CLASS="quote">The truth shall set you free!

Good to get some proof 130hp sohc zc my ***!</TD></TR></TABLE>

i dont know where you got that info from, but the dohc zc is 130 ps and the sohc is about 118ps...

but why would honda put a lower number down for the d16a6? there is no reason to espeically when it is the top of the line Si model's engine...i can see if we had the DOHC ZC here with ~125 hp and the d16a6 really had 120...

 

Ive never seen any real numbers from a japenese spec car like in a car and driver say with the sohc zc in it saying 118 hp. Ive only seen it advertised when someone is selling the motor.

I Have no problem with the sohc zc but I believe all it is is a glorified d16a6 Id never pay more for a sohc zc then I would for a d16a6 since they are in fact the same.

 

I guess that the only difference in the SOHC ZC and D16a6 is the valve covers....Oh yea and death to all those who said that the SOHC ZC had dome top pistons! Lies! That made me hold off a mini-me swap for a few days.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Superhatch &raquo;</TD></TR><TR><TD CLASS="quote">

ZC head stamp PM3-2


Modified by Superhatch at 5:28 PM 7/19/2004</TD></TR></TABLE>

Don't mean to Hi-jack your thread, but do you think that the 8/8 stamped on the your head stands for the year it was made(1988)? This is a pic of a SOHC ZC head that I worked on..it was an OBD1 sohc zc. Stamped PM3-12 with 9/3 (1993)? Kinda makes me think..

 

Keep in mind the exploration isn't finished yet

I still have to dissect the bottom end.

Here are a couple questions I have though.

1. Why would Honda make a motor with the exact same specs as the A6 and call it something else. I cant recall them doing that with any other engine.

2. Does anyone know anything about what the rest of the JDM ZC involves? Intake mani...exhaust mani....TB.... and most importantly ECU? Are they the same as the A6?

3. How do the two heads flow? I'm going to try to find a local shop that has a flow bench to see if both heads flow the same. Id assume if they have the same intake and exhaust port measurements they would...but you never know.

The thing that puzzles me most is the difference in names....

-Jake

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedRacerCivic &raquo;</TD></TR><TR><TD CLASS="quote">

Don't mean to Hi-jack your thread</TD></TR></TABLE>

Hi-jack with info like this by all means!

Very, very interesting. So a different head stamp all together. Im going to do a little internet browsing....bbl.

 

someone should throw in some more DOHC ZC info

 

Head codes....

Some info from this thread https://honda-tech.com/zerothread?id=786093

Shows that a 1991 Std D15B1 4sp has the head code PM9-3, which is the same as my A6 head code. My other A6 head has a code of PM3-7, and the other D series I have a D15b2 has the code PM3-23.

Are head codes irrelevent? What exactally do they mean?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxgator ESQ. &raquo;</TD></TR><TR><TD CLASS="quote">

i dont know where you got that info from, but the dohc zc is 130 ps and the sohc is about 118ps...

but why would honda put a lower number down for the d16a6? there is no reason to espeically when it is the top of the line Si model's engine...i can see if we had the DOHC ZC here with ~125 hp and the d16a6 really had 120... </TD></TR></TABLE>

Could it be that Honda reduced the numbers for the sake of the American
insurance industry? Imagine how hard it would have been to sell much
less insure a go cart with 160 hp? Car companies "fudge" the hp numbers
to make the cars more insurable..Make sense now.

 

And also for the sake of letting the 'luxury/high-end' company keep the spotlight.

In this case it would have been the Integra for America.

Likewise, look at GM.

The Camaro is rated at 320 HP, but the Vette at 350 HP. We all know the Vette does dyno a little more, but the run of the mill LS1 has way more than 320 crank HP!!!!

 

Could that be the reason for the name change as well? Does the ZC have a higher HP rating because it wasnt downplayed?

Interesting theory....

 

Hey one question Superhatch, was your jdm sohc zc, automatic? The sohc zc that my friend ordered was an automatic(torque converter, no flywheel). MAYBE the jdm sohc zc AUTO was downrated horsepower by having a D16a6 camshaft. Because I have heard of automatic B16 cams not being as aggressive as the manual cams. Maybe this implies to the Sohc JDM motors out there..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 4drEF &raquo;</TD></TR><TR><TD CLASS="quote">

Are you serious?

He has all the cam measurements up there.... or did you not bother to read?</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dr_latino999 &raquo;</TD></TR><TR><TD CLASS="quote">And the holy man hath said - be thy the same!</TD></TR></TABLE>

Oh My....

Don't you realize he lacks the instruments necessary to measure duration and lobe separation?

There is more to cam design than just lobe height.