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Discussion Starter #1
now, i have mulled this over plenty in my head.. and simply do not have a concrete answer.

i know that when switching to a big cam, it is advantageous to mill the head to increase the compression ratio. my question being. that on a mild build. for a dohc zc would the triflow cams from colt warrant the need for a compression bump.. the specs are as follows
Prim INT: 278° ADV duration / 198° @ .050 .430 Lift
Sec INT: 264° ADV duration / 192° @ .050 .420 Lift
EX: 276° ADV duration / 196° @ .050 .405 Lift
the plan is simple. just a bit more grunt. i/h/e cams and a tune. . im looking to make bolt on b16 power.. which i've seen in the 140-150 whp range. i just would like to think it would be attainable with modest well thought out parts.

im guessing i can switch to a real header design if that will produce more power over the 4-1 dc with collector mod.. but i'd sure like to keep p.s and ac in my ef sedan =). cheers...
 

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I know it is a bit of work, but the only way to really know how much piston to valve clearance you have with your cams is to clay the motor, then you know how much you can safetly mill. It's too early and its a holiday, so hopefully someone else will chime on and be more specific.
But on another thought how does your ps bolt up? I'm not familiar with dohc zcs specifically, but on my y7 the bracket bolts onto the block and the head, and after I had my head milled the top bolt for the head did not want to go in because it was shorter. You could probably just notch your bracket if you run into problems.
 

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Talk with Acid BEaver. he knows these motors VERY VERY Well and has helped spec some nice DOHC ZC motors. He also has spec'd and tuned a DOHC ZC with Triflows and custom header.
 

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If you have low compression like Vitara pistons you need to remove up to 2mm, but for a stock piston setup you should not remove that much. The trouble with the DOHC is the high dome pistons and large chambers. I've removed 0.030" off DOHC heads before and that puts compression in the 10.3-10.6:1 range, which is perfect for a street setup on stock cams.

With your cams you will really have to check valve/piston clearance. So if I were you I would install the cams and check clearance before even milling the head.

I've seen NA DOHC ZC make 130-140whp with stock cams so I think your goal of 140-150whp is reasonable.
 

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Talk with Acid BEaver. he knows these motors VERY VERY Well and has helped spec some nice DOHC ZC motors. He also has spec'd and tuned a DOHC ZC with Triflows and custom header.
the last he told me he still has not used tri flows, only colts race grind cams for the dohc zc

i would contact jeff at colt cams, he would most likely know how much you can safely mill the head
 

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He won't tell you how much you can mill it.

You can mill ~2.7mm before hitting the valve seats. (#*$()*#$ you, SOHCs.

You will simply make a lot more power milling the head, however, I don't like milling the head too much with stock pistons. I wouldn't go more than 1.5mm, but not for clearance issues (you can whack the head a lot more without issues thanks to the huge valve pockets on the pistons), but for flame propagation issues. JLI found no benefits to milling the head more than about that amount with stock pistons. If you went with good aftermarket pistons, or even the NPR P29s, you could mill more and have a better overall chamber with more quench action, leading to more power. For most NA Ds, I think 12.5:1SCR is a good sweet spot for pump gas, if you can tune.
 

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He won't tell you how much you can mill it.

You can mill ~2.7mm before hitting the valve seats. (#*$()*#$ you, SOHCs.

You will simply make a lot more power milling the head, however, I don't like milling the head too much with stock pistons. I wouldn't go more than 1.5mm, but not for clearance issues (you can whack the head a lot more without issues thanks to the huge valve pockets on the pistons), but for flame propagation issues. JLI found no benefits to milling the head more than about that amount with stock pistons. If you went with good aftermarket pistons, or even the NPR P29s, you could mill more and have a better overall chamber with more quench action, leading to more power. For most NA Ds, I think 12.5:1SCR is a good sweet spot for pump gas, if you can tune.
the beaver is correct, we have tried different things with ours to raise the compression and find that if you remove more than about 1.5 mm from the head, it starts to hurt you more than help - if you have stock pistons, first deck the block 1.0mm, and then mill the head to get the compression ratio you can live with, rather than taking it all off the head - in addition to the block, 1.0mm from the head would give you about 11.6:1 and 1.5mm would give you about 12.3:1 - taking it off the block rather than the head keeps the area of the combustion chamber around the dome a little larger for better flame travel - we have milled the head 2mm and decked the block 1mm using stock pistons and stock head gasket and had no clearance problems using stage 4 camshafts - we had around 0.190" clear from piston to valves before milling - the closest the pistons come to the valves is at TDC on overlap where the exhausts are just about closed and the intakes are slightly open - the lift on our stage 4 cams at TDC on overlap is 2.74mm (0.108") on the intakes and 1.25mm (0.049") on the exhausts
 

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Discussion Starter #12
i've drawn my conclusion and im going to leave it be.. if im still not happy with it.. ill just throw some boost at it.. keep ps and ac.. lil baby boost dohc zc. thanks for your insight fellas.. ill keep ya updated..
 

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Discussion Starter #14
These things love boost. =)
i love boost as well.. and im not against it.. just have always been so boost oriented.figured i would play with this n/a for a min... after my exhaust.. ill boost this.. modest goals.... (did i mention it already has arp head studs ). hehe boost is always in my back pocket =P
 
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