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89 EF 4wd sedan
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505 Posts
Discussion Starter #1
Hi everyone,

i've been building a JRSC DOHC ZC which has been running for a while, but i've taken it off the road to go with forged rods/pistons as well as some head work and aftercoolers.

Anyway i'm trying to find a piston to suit my application. What i've found so far is the 75.5mm Wiseco d16a1/ZC piston which drops the compression to 9.1 in a d16a1 (i'm waiting from specs from race engineering to confirm what compression ratio i'll get in my ZC). If it's a 9.1 CR in a d16a1 though, my guess is i'll be getting high 8's CR in my blacktop ZC which is too low IMO.

Another alternative that i've read you can use it high compression SOHC pistons. Specifically, i've got my eye on CP Carillo D16a6 pistons 11.0:1 CR, which if i'm using the online calculator that's floating around yields me a 9.5:1 CR which is what i'm after.

Does anyone have experience with using high compression SOHC pistons in the blacktop ZC? I wish thezcr was still around.... :(

Pics for attention:





 

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Premium Member
90 crx si/96 accord
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788 Posts
Iirc, lurker, from thezcr, used high comp z6 pistons (super tech maybe) I know it was for the z6, and not the a6.

To.contact matt, all you have to do is view his profile, go under contact and it should drop down to his email.
 

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Brokedick Millionaire
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If Matt isn't too busy, and I know he is swamped with Funk's race car issues.

But I have been texting him updates on his transmission I'm building :)
 

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Registered
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Hi everyone,

i've been building a JRSC DOHC ZC which has been running for a while, but i've taken it off the road to go with forged rods/pistons as well as some head work and aftercoolers.

Anyway i'm trying to find a piston to suit my application. What i've found so far is the 75.5mm Wiseco d16a1/ZC piston which drops the compression to 9.1 in a d16a1 (i'm waiting from specs from race engineering to confirm what compression ratio i'll get in my ZC). If it's a 9.1 CR in a d16a1 though, my guess is i'll be getting high 8's CR in my blacktop ZC which is too low IMO.

Another alternative that i've read you can use it high compression SOHC pistons. Specifically, i've got my eye on CP Carillo D16a6 pistons 11.0:1 CR, which if i'm using the online calculator that's floating around yields me a 9.5:1 CR which is what i'm after.

Does anyone have experience with using high compression SOHC pistons in the blacktop ZC? I wish thezcr was still around.... :(

Pics for attention:





very nice set up, i respect clean and proper builds, youve accomplished that for sure.

i have no info as far as what pistons are the right pistons for a dohc zc.

i run je 11:1 pistons in my built a6. acid beaver would be the guy to ask about what pistons you can and should run.

can i ask who makes that header ? did it fit with the factory crossmember or are you running an aftermarket crossmember/traction bar system ?

have an instagram ?

stratton.
 

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89 EF 4wd sedan
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505 Posts
Discussion Starter #9
Iirc, lurker, from thezcr, used high comp z6 pistons (super tech maybe) I know it was for the z6, and not the a6.

To.contact matt, all you have to do is view his profile, go under contact and it should drop down to his email.
I'm just looking through the CP piston catalogue, and it looks like z6 pistons are about 0.5:1 less compression than the a6. So would get me about 9.0:1 which isn't bad.

Yeah it says i need to work up 20 posts before i have permission to contact members by email.
 

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89 EF 4wd sedan
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505 Posts
Discussion Starter #11
very nice set up, i respect clean and proper builds, youve accomplished that for sure.

i have no info as far as what pistons are the right pistons for a dohc zc.

i run je 11:1 pistons in my built a6. acid beaver would be the guy to ask about what pistons you can and should run.

can i ask who makes that header ? did it fit with the factory crossmember or are you running an aftermarket crossmember/traction bar system ?

have an instagram ?

stratton.
Yep, you can find me on Insta my tag is the same as my plate 'efb055'.

The header is an eBay special for a B20, it's a stainless construction and the pipes seem to be put together ok. The flange was mild steel though which didn't matter, because i cut it off and plasma cut my own header flange to suit the ZC





New flange, the pipes needed to be pulled with clamps... The port spacing is noticeably different between the two motors. The dohc zc has equal ports, whereas the B seems to have the outer two closer to each other.



And I had to modify the downpipe to clear the 4wd transfer case:

 

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Tape-R taper/driver
EC3, ED8, ED9, EE5
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Nice, we didn't get the RT4WD sedans or DC Integras here. Just the wagons.
 

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for good quality high comp pistons, you could try PG6 honda pistons and shave the head down to match your wanted compression.

I think there are still one or two companies making adjustable cam gears to match the head shave.
 

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89 EF 4wd sedan
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505 Posts
Discussion Starter #15
for good quality high comp pistons, you could try PG6 honda pistons and shave the head down to match your wanted compression.

I think there are still one or two companies making adjustable cam gears to match the head shave.
I've got JUN adjustable cam gears because i'm running bisi cams... What difference does shaving the head make to the design of the cam gear? Is it just that you need to be able to adjust them to optimise valve to piston timing/clearance?
 

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BATSLOMAN GIVES NO FUCKS.
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fucking drooling over that exhaust
 

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2005 Legacy GT
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Hmm, my engine builder just suggested to look through catalogues and see what pistons are the right size. I worry that the valve reliefs would be at the wrong angle or not deep enough or something like that.
I only mention it because I saw an older civic (like EB chassis or thereabouts) running some older Goldwing pistons.

I've got JUN adjustable cam gears because i'm running bisi cams... What difference does shaving the head make to the design of the cam gear? Is it just that you need to be able to adjust them to optimise valve to piston timing/clearance?
As you shave the head the distance between the crank and the cam changes, so the timing requirements also change slightly. I can't remember exactly, but I think you have to slightly retard the cam timing as you mill the head down to keep the mechanical timing in it's optimal place. Or something along those lines.

Someone correct me if I'm wrong on that. I have end of work day brain.
 

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89 EF 4wd sedan
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505 Posts
Discussion Starter #19
I only mention it because I saw an older civic (like EB chassis or thereabouts) running some older Goldwing pistons.
Cool, i'll have a look into it.

As you shave the head the distance between the crank and the cam changes, so the timing requirements also change slightly. I can't remember exactly, but I think you have to slightly retard the cam timing as you mill the head down to keep the mechanical timing in it's optimal place. Or something along those lines.

Someone correct me if I'm wrong on that. I have end of work day brain.
Oh right, it makes sense... I'd guess the tensioner would pickup the slack too.
 

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as you reduce the head height via shaving, you want to adjust the cam gear so the center stays lined up, but the gear teeth are allowed to slowly roll clockwise as it gets shaved.

generally its less than 2 degrees of affective movement, but that can make a significant impact (positive or negative) on how you can time it.

and I pulled that 2 degrees movement out of my ass. it can be smaller or larger obviuously based on how much is shaved.

but then, shaving the head tightens up the combustion chamber and generally improves chamber burn events
 
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