Z Engine Questions

[Nissan_Boy85]

So I've been reading around on multiple places, but have yet to come up with an answer that makes sense to me. Would it a good idea to run a Z22 head on a Z24 block? I guess my question has multiple parts, so here it goes...

 

A: Is it true that the Z22 head flows better then the Z24?

B: Would the Z22 head be a direct bolt on for a Z24 block (talking about gasket, oil and coolant passages)?

C: Is it worth the effort if the answer to part B is no? 

D: Will the Z24 intake and exhaust manifold's bolt to the Z22 head?

E: Which intake would I want to use if answer to part D is yes, the Z22 or Z24?

F: Is there a combustion chamber size difference between the Z22 and Z24?

G: Would the Z22 head change the compression ratio? What would it change it too or how would it change it?

H: Should I consider a Z20 or L20 head at all?

 

I think that's it for the time being. I know that guys have done Z22 top and Z24 bottom, but they wern't specific with what they did, or at least for what I saw (if I missed something point me in the right direction). I'm going to be running KA24E OE pistons on Z24 rods in a Z24 block fersure. I have a Weber 32/36 that I will be using for a carb. I'm just not sure if a Z22 head would be worth it or not. If what I'm thinking is all correct, it will. I just need answers, and I'm sure the answers will bring more questions. School me guys!

 

[HotRodDatsun]

The best Head is an L series V912..  Now if you cant fork out that change and want a Naps Z head..  The 1980 Z20 4 Plug Carb Head has the smallest chamber and flows the same as the Z22..

 

( I have over 15 NapsZ motors in my Trailer behind the Shop.. Raced them for years )

 

Call if you have Questions 404-374-5498

[datzenmike]

So I've been reading around on multiple places, but have yet to come up with an answer that makes sense to me. Would it a good idea to run a Z22 head on a Z24 block? I guess my question has multiple parts, so here it goes...

 

A: Is it true that the Z22 head flows better then the Z24?

Not that I'm aware of. The Z20 and Z22 intakes ports are somewhat smaller and round. The Z24 ports are slightly larger and square with rounded corners.

 

 

B: Would the Z22 head be a direct bolt on for a Z24 block (talking about gasket, oil and coolant passages)?

Other than the above they are the same, even the combustion chamber size.

 

C: Is it worth the effort if the answer to part B is no?

I don't think so unless the Z22 head is all you have as a replacement.

 

D: Will the Z24 intake and exhaust manifold's bolt to the Z22 head?

Yes, the bolt pattern is the same but the intake port shape isn't exact match to the Z22's intake port.

 

E: Which intake would I want to use if answer to part D is yes, the Z22 or Z24?

I would run the Z24 because larger but the Z22 is a perfect match.

 

 

F: Is there a combustion chamber size difference between the Z22 and Z24?

I've measured 2 Z24, 2 Z22 (truck) and 2 Z20E heads... all the same combustion chamber size. Z20 and Z22 were identical round ports even had the injector notches, but the '80 non California and Canadian Z20E heads were only 4 plug, '81 were 8 plug.

 

 

G: Would the Z22 head change the compression ratio? What would it change it too or how would it change it?

No, see G above.

 

You could mill the head surface. Each mm (0.040") removed will decrease the combustion chamber at least 6cc. On a stock Z24 a 1mm shave will up the compression from 8.25 to 8.8

 

Over boring 1mm and going to a 1mm over size piston would up the compression to only 8.39.

 

Installing stock bore KA24E pistons will up the compression to 9.47.

 

There is a smaller combustion chamber Z20 head out there. I only know it from the 720 Mileage Option motor. The combustion chamber is around 45cc and if used on a Z24 the compression would be around 9.47 used also with a KA piston about 11.76

 

 

H: Should I consider a Z20 or L20 head at all?

If you want compression and can find one of these Mileage Option heads (may also have been used on the '80-'81 A10 car but not sure) then yes otherwise no advantage.

 

 

The best Head is an L series V912.. Now if you cant fork out that change and want a Naps Z head.. The 1980 Z20 4 Plug Carb Head has the smallest chamber and flows the same as the Z22..

Best all out breathing L head would be the LZ and OK Giken 16 valve twin cam or the earlier FIA casting L heads. Impractical for the street or wallet. This leaves the early L16SSS 219 head or the later reissued V912 L heads. But any talk of an L head completely changes the motor away from a cross flow Z.

 

You mention the Z20 head being smaller combustion chamber. The two 4 plug '80 and '81 Canadian Z20E heads I have are identical to the Z22s and the Z24s that I have. The Z20(S) from the 720 IS smaller but 8 plug. I don't have one but I have pictures of it.

 

Note the small quench areas on intake and exhaust sides. These are around 12cc smaller than the regular Z series heads.