89 crx dohc zc swap. milled head.

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bannacrx

New Member
i swapped a jdm dohc zc into my 89 gutted crx. ive got a coldair, apexi catback exaust, and bigger plug wires with ngk sparkplugs (no biggie there).

question is, ive heard that shaving the head 1.4mm will increase the compression to 10.6:1. is this true, and what kind of power gains am i looking at? thanks.
 
Why? Oh so piontless. Drivability will suck. Put that interior back in your Rex, its not saving you any weight. Boost the ZC and be happy going fast.
 
milling the head 1.4mm on the DOHC ZC using a stock head gasket will raise the compression ratio to 10.87:1 - with that much milled from the head, you would have to get adjustable cam gears - unless you add bigger camshafts and a bigger throttle body in order to take advantage of the higher compression ratio, it is going to hurt the performance - you would also need to have a chipped ECU in order to supply more fuel and to better control the ignition timing - you would need to determine what is required for fuel and timing by some serious dyno tuning - having tried all kinds of different higher compression ratios on the ZC (all the way up to near 14:1), i can tell you that you are better off leaving the compression alone
 
Hy guy's! New here! I know this post is old but didn't find anything better topic the this here.I have an issue with my d16z5 DOHC (same as d16a9) milled the head 1mm and now a valve is knocking at the 2nd piston. I'm also runing stock cams, valves and springs. Before I take the head off to change those valves I want to make sure I'm doing anything right or something wrong.timing is now 6 degree retarded and car runs very smooth but knocks
 
Hy guy's! New here! I know this post is old but didn't find anything better topic the this here.I have an issue with my d16z5 DOHC (same as d16a9) milled the head 1mm and now a valve is knocking at the 2nd piston. I'm also runing stock cams, valves and springs. Before I take the head off to change those valves I want to make sure I'm doing anything right or something wrong.timing is now 6 degree retarded and car runs very smooth but knocks
First thing you should do is make sure the camshaft timing is correct - having to run it at 6 degrees retarded would lead me to believe the cam timing is not right - with the cam shaft timing correct you shouldn't have any piston to valve clearance problems with 1mm milled off the head - we have run the DOHC ZC with 2mm off the head and an additional 1mm off the block and still had plenty of piston to valve clearance - if you had a piston to valve clearance problem, it would be on all cylinders, not just one - noise from the valves could be from valve clearances not adjusted properly
zccamtiming.jpg
ZCtiming.jpg
 
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