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Block/Head Questions


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I am looking at options for the engine build on my '73 240z. The car came with a L24 (E88/P30) in it, that ran when pulled. When I bought the car it came with an L28 (N42 block/ N47 head). I have not opened up the L28 to inspect it, but the engine does seem to turn freely. I don't know anything else about the history of the motor.  I would like to work with what I currently have. I have done my research but, it all gets so confusing. I am  interested to know if the L28 setup would be worth attempting to turbo? I know that the P90 is the preferred head when it comes to going turbo, but that is proving hard to find. What would be recommended to make this setup work with a turbo? Remove the liners in the exhaust ports? Pistons (flat top or dished)? What else would I have to do? At this point am just looking at whether or not I have a good base to start with or just wasting my time. I am looking at making this car into a 300hp daily driver.  Is this realistic with what I have or am I just dreaming? This is my first build so please bare with me.

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General rule is the liners are bad for turbo charging . You could just run a small amount of pressure on the L24 /88. They aren’t that high of CR. 300HP is a nice goal , but maybe just go for 200+ and get your feet wet learning these motors . Learn on your first motor and invest bigger $$ when your knowledge gets better 

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The N47 head (if I remember correctly) has a good combustion chamber like the P90, but the liners can be risky for a turbo. That being said, some people have made their head flow WORSE by removing them and not doing things properly. 

 

As far as pistons go, flat tops are actually great with a P90 if you have a standalone ECU. Nissan ran VERY conservative boost and compression with the now primitive efi. You can make more power on a stock block just by improving the efi. 

 

If you don't have a P90, stay with dished pistons, as flat tops will get you into NA compression territory for these motors, and the worse combustion chamber design of the earlier heads will severely limit you if you're really intending to boost. 

 

All that being said, Big Phil (turbo280z on youtube) ran an N47 head for a long time in his turbo L28 with good results until he switched to an RB30 build. 

Edited by Zetsaz
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Actually that is incorrect . The P79 is the head with liners and has similar combustion chamber to the P90. N47 head is usually close to the bottom on preferred heads .

Removing liners should be last resort . There have been successful turbo builds with liners , but the liners were better installed on later model heads - p79 and Maxima N47. 

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On 11/11/2020 at 3:58 AM, madkaw said:

Actually that is incorrect . The P79 is the head with liners and has similar combustion chamber to the P90. N47 head is usually close to the bottom on preferred heads .

Removing liners should be last resort . There have been successful turbo builds with liners , but the liners were better installed on later model heads - p79 and Maxima N47. 

 

AHH! Sorry, mixed up the N47 and P79 in my head. Thank you for the correction. 

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  • 4 weeks later...
On 11/8/2020 at 2:06 PM, dasboikee said:

I am looking at options for the engine build on my '73 240z. The car came with a L24 (E88/P30) in it, that ran when pulled. When I bought the car it came with an L28 (N42 block/ N47 head). I have not opened up the L28 to inspect it, but the engine does seem to turn freely. I don't know anything else about the history of the motor.  I would like to work with what I currently have. I have done my research but, it all gets so confusing. I am  interested to know if the L28 setup would be worth attempting to turbo? I know that the P90 is the preferred head when it comes to going turbo, but that is proving hard to find. What would be recommended to make this setup work with a turbo? Remove the liners in the exhaust ports? Pistons (flat top or dished)? What else would I have to do? At this point am just looking at whether or not I have a good base to start with or just wasting my time. I am looking at making this car into a 300hp daily driver.  Is this realistic with what I have or am I just dreaming? This is my first build so please bare with me.


If you are looking for a 300hp daily driver, you need the L28et pistons or custom/forged. The ring/piston design can be reliable for thousands of miles on a good tune. Stock L24/28 pistons will not last. At best your ring life is greatly reduced. Keep an eye on your CR as well. There is plenty of information on here about what head/block combos will yield. You should not exceed 8.3, but ideally you should be below 8. 
 

if you want to stick with NA pistons, run a much less ambitious boost (8 psi) with a good IC to bring down your induction temperature. I still think you will be unhappy with the ring life but if you plan to pull the block eventually, you don’t have much to lose. 
 

As far as the head, I second getting a P90. I don’t have any experience running any other head on a turbo application. I will have a P90a with hydraulic lifters for sale in about 3-4 months once my P90a with solid lifters gets rebuilt. 

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