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....
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.
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.
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:
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?
It was a bit of a C*** to get working (it also fouled my top radiator hose position, but it looks pretty neat now that it's in there. I'm hoping it performs well when i go back to the dyno.
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
Just an update, I ended up ordering the 75.5mm Wiseco d16a1/ZC pistons and Eagle rods. I'll just end up shaving the block to bring the CR back up to what i'm after.
Oh my bad I thought they were going in a SOHC because of the title.
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