I'm using a pm-7 with a Mugen chip. How much can the head be safely milled and still run pump gas (93). I was hoping to get the C/R about 11 to 1. Any help would be appericated. also I'd like to here from peeps that have done it and not just something you heard about. and what kind of ing/ecu/fuel set-up did you use. TIA

 

you can mill it .4mm and get 10.0.1 comp or you can mill 1.4mm and get 10.6.1 comp safely on pump gas. i have mine at 1.4mm run's good on pump gas and i have the s afc for fuel man and a chiped si ecu

 

i read 1.4 millimeters is max you should do safely without messing up the timing, can anyone second that? thats my plan for this summer, along with a cometic headgasket. can someone who has done this post some results? i'm shooting for a little over 130 or 140 hp at the wheels with cams and all the bolt ons.....i'm not sure what i'm at now, my header is sitting next to my desk anyways, the factory dx manilfold SUCKS for the zc....homemade header all the way...just needs to get coated.

 

I will Second your Post, Currently my ZC Head is milled 1.4mm, and I am running ZC Bros Stage 2 Cams. I haven't had any problems with the car. To get 11.0:1 Compression I dont recomend you Mill the head.....1.4m is the absolute max you can mill the head. Dropping on a Thinner headgasket might get you to 11.0:1 but I dont recomend it cause you will have no Clearance. I had to Notch my Headers to fit after the milling as the flange stuck out a slight bit and bumped the Block.

Fuel Set up for me is a ZC Bros Tuned ECU, and S-AFC.....Along with 89 Teg Dizzy, MSD Blaster 2 Coil, and MSD 8.5mm Wires

Later,
Mike
'88 CRX "ZC REX"

 

I have a D16A9 which is said to be identical to DOHC ZC. I want to raise the CR by milling the head. I want to be sure that D16A9 is absolutely identical to DOHC ZC and 1.4mm off the head is safe. Anyone can help me?

 

Old thread.....2003!

 

still waiting for answer

 

the A9 and ZC heads are identical - 1.4mm off the head is completely safe with the stock pistons, however, for the best results it would be better to take 1mm off the block and 0.4mm off the head - we have tried several different combinations and have taken as much as 1mm off the block along with 2mm off the head, using stage 4 camshafts, with no clearance problems - this combination yields measured compression ratio of close to 13:1, however, it didn't produce any more horsepower as it did with 1mm off the block and 1.5mm off the head which was about 12.2:1 compression ratio - with more than about 1.2mm off the head, the combustion chamber gets to be too small to allow good air flow in the chamber - if you aren't in a position to take anything off the block, then you will be o.k. to take the 1.4mm off the head

edit - just be sure that the head hasn't been previously cut before you take anything off the head

 

How much the horsepower will be increased with stock headers, cold air intake and a good tune when the compression ratio is increased to 10.6:1? I also want to do a mild port and polish, so I think I will be happy with the final results.

Another way to go is to port and polish the head and mill it for 10.0:1 C.R. to get better fuel economy and boost the engine to about 8psi with a centrifugal supercharger, which is expected to give me a significant high end torque. Is this block capable of this?

 

How would a machinist detect that?

 

by measuring the height of the head - height new is 132.0mm