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Z series head differences


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I have looked everywhere without luck. I have a z24 but thinking of putting a z20 4 plug head on it. So I am trying to figure out about the chamber size, valve size and cam size. I know if the valves are smaller on the z20 head then it wouldnt be worth the time so swap as I am trying to do a cheap build with what I have access too. I also have access to ka pistons and connecting rods for a car ka that I would think would work in a z24. Any and all help would be greatly appreciated. If had everything near me I would measure myself.

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Car KA rods will not work in a Z. The journal size of the ka rods is narrower than the z rods.


Why the 4 plug head? You could do the same thing by plugging half the plugs on your current head and adjusting the timing. But the only benefit is aesthetics really.

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KA24E rods will fit any L20B Z20 Z22 or Z24 crank. Small end may be slightly too wide to properly fit a Z24 piston. It will fit but the pin has to be able to shift side to side slightly to fit variances in the crank and bore spacing. I think someone here had to mill 0.012" off each side.


KA24E from a 240sx are fully floating so the pin is not contained by C clips in a Z24 piston. Use KA24E truck rods do press into the rod and are ok.




Z20 heads from an A10 should be fine but if from a 720 Z20 the combustion chamber is much smaller and will raise the compression

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I forgot about the sloposition on television big end and yes these are from a car ka. Just trying to figure out to hump the performance a little since I am going to do a head gasket before hand and regasket everything. So if I run the sohc ka pistons and z20 head. What would the compression be datzenmike

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My Z24 and Z20S head, both upside down

Z20 heads are the same as the Z24 head except the intake ports are smaller and round, the Z24 heads are square-ish with rounded corners. '80  were 4 plug outside of California and  ALL were 8 plug from '81 on. If possible keep the 8 plug head there is no gain going to a 4 plug head. You can run much less ignition advance with twin plug design.


If you should find a Mileage Option 720 Z20 ('83-'86) they do have a smaller combustion chamber.


Z24 with either Z24 or Z20S / Z20E or Z22S / Z22E heads from 200sx 2 or 4 plug design, all the same, with KA24E pistons.... 9.52 compression


Z24 with mileage option Z20 head from 720 with KA24E pistons....................................................................... 11.28 compression

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