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3.2 Build EFI N42 / MN47


madkaw

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Just thought I would start another thread . This was supposed to be a L28/54 MN47 , but it ended up with a Rebello prepared N42 /MN47. 
The N42 was sent to Rebello and he prepped it for JE 89mm 

pistons . LD crankshaft offset ground with Eagle rods to get me 3.2 
The MN47 head was ported by me - no flow bench , just seat of the pants cutting. Ports were only opened up to 35mm  . Manely 44/35 swirl valves with bronze guides . The head is at 39cc . The cam is a 535 lift Bonk cam . It’s advertise 535 , but I could only get that with 0 lash , so it’s more like 520 lift .

Engine management is a Megasquirt 3X with 270cc 14mm injectors running on a stock N42 intake with a 240sx 65mm TB . 

Exhaust is a MSA 6-2 header with dual exhaust to the back . 
BHJ damper , Kameari oil pump and chain tensioner . 
GM alternator 90 amps

D-585 ignition coils with MSD wires . 
4 row radiator with single electric fan 

cam sensor from 4.0 Jeep modified by me . 
flywheel 12lb steel that doubles for my CAS . 

 

Currently rev limiter is set at 7500 . Power drops off before then with current cam and induction .His build wouldn’t have happened except for the knowledge base on this site . Thanks for all that contributed their knowledge . Dyno session is schedule a month out . Currently using butt dyno and GPS speedo to do 0-60 times . It will also do quarter mile . Best time is 4.77 to 60 with some tire spin . Timing is 37 degrees max with a 13.0 set for WOT AFR. 

 

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Edited by madkaw
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57 minutes ago, Derek said:

I'm doing exactly the same bottom end and after hearing that now I really need to move it along. Sounds great.

 

You know a KN20 head would solve that pesky power drop off problem:)

Believe me - I drool about it a lot .  A better inductions system would still help in the meantime 

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I left the decision with Dave Rebello. I know he can offset bore to get the most out of the block. I also went with a N42 block after reading it had the highest nickel content and a better chance of being bored higher. Maybe because of the structure of the block . He must have felt pretty confident because I told him that there is a possibility of running as a turbo with a different head . I do not know what wall thickness I ended up with .

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On 9/25/2020 at 4:48 AM, madkaw said:

I left the decision with Dave Rebello. I know he can offset bore to get the most out of the block. I also went with a N42 block after reading it had the highest nickel content and a better chance of being bored higher. Maybe because of the structure of the block . He must have felt pretty confident because I told him that there is a possibility of running as a turbo with a different head . I do not know what wall thickness I ended up with .

We went through 5 N42 blocks before we found one that sonic tested and the machine shop said could take the 88.5 bore.  

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16 hours ago, DuffyMahoney said:

We went through 5 N42 blocks before we found one that sonic tested and the machine shop said could take the 88.5 bore.  

I guess it also depends on what the builder decides is the safe minimum wall thickness too! 
Maybe Dave pushes the envelope or is basing it on his experience . I told him I would be pressurizing , but it would be lower psi , higher CR build if anything . Maybe I just got lucky 

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Well it’s harder to get an appointment with a dyno than my doctor . I’m booked out to November . Business is good enough that most shops don’t want to give up there dyno to walk ins , they have so much in house projects . 
It’s all corvettes and Mustangs , etc.. 

I did upgrade my injectors to 42 lbs and re-tuned with success. Did another 4.77 split , so happy . Might play with valve timing a little to get more top end, but I think I’m at the end with the N42 intake . 
My buddy is converting a diesel intake for me to run EFi . I’ll go from 31mm runners to 35mm and looonger runners . It will be interesting .  

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On 9/30/2020 at 10:07 PM, madkaw said:

My buddy is converting a diesel intake for me to run EFi . I’ll go from 31mm runners to 35mm and looonger runners . It will be interesting .  

 

I am doing my own turbo build and was thinking about using the early EFI intake manifold flange with maybe 2" worth of the original intake runners as the base for fabricating a bigger runner manifold.  I cut off the rest of the manifold.  Do you have another one of those diesel manifolds or can you post a picture please?  

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13 hours ago, AydinZ71 said:


look at that torque drop off! You got room to run! If you can improve the head flowrate, You can bump up your HP quite a bit, even if you didn’t add a single peak ft-lb of torque. 

I contend that it’s more intake manifold then head . Stock plenum 

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8 hours ago, madkaw said:

I contend that it’s more intake manifold then head . Stock plenum 

 

Could be for sure! It is flow-limited based on the linear(ish) torque drop-off. If you are confident the intake manifold is the largest factor, Protunerz out of Ottawa makes a custom intake manifold with larger TB. I purchased as a bundle with turbo exhaust manifold and downpipe. Looking forward to seeing the build quality when he is finished sometime in Feb. Let me know if you want me to make some measurements when I receive mine. 

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22 hours ago, AydinZ71 said:

 

Could be for sure! It is flow-limited based on the linear(ish) torque drop-off. If you are confident the intake manifold is the largest factor, Protunerz out of Ottawa makes a custom intake manifold with larger TB. I purchased as a bundle with turbo exhaust manifold and downpipe. Looking forward to seeing the build quality when he is finished sometime in Feb. Let me know if you want me to make some measurements when I receive mine. 

Got one in the works now with tapered runners . Stock manifold has 31mm runners . New will be 44-37mm

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