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こんにちは,

It's been a while since I have been on but we are finally in our new home and I have had some spare time to pull the z apart.

So my question is, what would be the best build for a n42/n47 na set up? That's the block and head I have right now and I believe it shouldn't be a bad place to start. Any of you have experience with this build? I have read mountains on the n42 head but I can't find much on the n47. From the few things I have found some good ideas might be replacing the dished pistons for flat tops. From familiarity on the head I assume it would bring compression up to about a 10:1 and you would have to be crazy to not put a new cam in after that. (270 - 280 degrees on that cam, correct?) After that you would want your head matched up to your exhaust and intake for better flow. What else might you want to do? I currently am running round top SUs and the stock exhaust. The exhaust will be replaced for 2.5 and, if dreams come true, I will switch to some triples. What ideas can you folks dream up for this motor/head? I am not looking for any crazy power upgrade, just something to put a smile on my face. I wan't to make sure I can still daily it without putting racing fuel in it. :D

Thank you in advance, the support I get from this forum by far makes it my go to place.

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If you could find a zx motor from a junkyard and use the flat top pistons and the p79 head you would be better off in my opinion. The n47 is the least desire able head there is. 

Google datsun z motor calculator and try different components. The n42 head would be able the first one with bigger valves already then the n47, then the better p79. Google " diseazed motor build classiczcars.com" or go to datsungarage.com and find the motor sub category and then the cylinder head mod.

I can post those links in the morning as I have them bookmarked on my laptop.

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12 hours ago, siteunseen said:

I can post those links in the morning as I have them bookmarked on my laptop.

Good stuff here if you haven't already read it. :)

datsunzgarage.com, http://datsunzgarage.com/engine/

P79 head, http://datsunzgarage.com/p79/

Cylinder heads in general, http://datsunzgarage.com/heads/

Engine calculator, http://atlanticz.ca/zclub/techtips/calcs/engine builder/index.html

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site, the N47 head is essentially the same as the N42 head.  Nissan added the exhaust liners for cleaner emissions but didn't change anything else.  So if you're not planning to do any porting work, or add a turbo, the two are about the same.  The N47 typically comes with the oiler cam also.

With carbs, exhaust and cam are probably the simplest power increasers.  Increase air flow through the engine.  After that, port work on the head.  But even with port work, it's mostly intake, not exhaust.

There is a lot out there about how effective compression ratio increases really are.  They don't do much, on their own.  I would read up on CR and its effects before going to the trouble of installing flat top pistons.

There's a lot of money you can spend without really gaining much.  Plan first then act.

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Would the N47 work as well with flat topped pistons compared to a P79?  I wasn't really recommending an N42 just stating it was the first one with the bigger valves.  Sorry for any confusion. :)

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People report mixed results when raising the compression ratio by using flat top pistons.  Apparently, fuel quality differs across the states so some people get knocking and others don't.  If you don't shave the head the N42 or N47 gets you almost 10:1.

http://www.ozdat.com/ozdatonline/enginedesign/

There are so many opinions out there it's crazy.  Some people like the rumpety-rump cam noise, some like the 7500 RPM screamer, some like the torquey 3.1 liter engine.  RM needs to decide what makes him smile, I'd say, and get those details.

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Damn, the site is getting Gallery imaged again...  Hate it when that happens.

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49 minutes ago, Zed Head said:

People report mixed results when raising the compression ratio by using flat top pistons.  Apparently, fuel quality differs across the states so some people get knocking and others don't.  If you don't shave the head the N42 or N47 gets you almost 10:1.

http://www.ozdat.com/ozdatonline/enginedesign/

There are so many opinions out there it's crazy.  Some people like the rumpety-rump cam noise, some like the 7500 RPM screamer, some like the torquey 3.1 liter engine.  RM needs to decide what makes him smile, I'd say, and get those details.

I like the torquey 3.1 liter, 7500 rpm screamer that goes “rumpety-rump!”   :beer:

Edited by Diseazd
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22 hours ago, siteunseen said:

Would the N47 work as well with flat topped pistons compared to a P79?  I wasn't really recommending an N42 just stating it was the first one with the bigger valves.  Sorry for any confusion. :)

I believe the 79 head has a bigger combustion chamber so compression would much less , but doable with flat tops.  79 head has the better of the combustion chamber shapes - which helps with fighting detonation. 

So many choices ....

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Thanks for the replies!

A thought to consider. With flat tops in the p79 head, wouldn't you just have a zx motor? Siteunseen, those are great reads, loads of information on there.

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2 hours ago, Rij Martin said:

Thanks for the replies!

A thought to consider. With flat tops in the p79 head, wouldn't you just have a zx motor? Siteunseen, those are great reads, loads of information on there.

Yes it would be  ZX motor, pretty much but the reason they did the flat tops on the zx was to make up for the power to weight ratio. Zxs are a good bit heavier, they have power steering power windows and heavier safer bumpers. 

Knowing now what I've learned on this forum I would definitely go with a zx motor in my light Z. The p79 has better fuel quench and like Madkaw says lowers the risk of pre detonation I think they call it or "pinging". That will eat up your pistons.

I've been told my n42 block with flat tops and my n42 head would be a good motor/head combo. I have the flat tops and eventually will swap them in place of the dished I'm currently running but it runs so good now, not a performance motor just good running dependable motor I cant make myself tear it back apart for a little more power. The police keep me from building a hot rod. LOL

Good luck and don't worry about asking, we have plenty of opinions for all the choices you're up against. 8^)

Cliff

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Just remember that the power is in the head and tune on this motors. Any serious monies should be on the head ( cam, valve job, ) and induction system. Of course if want a decent bump in power you want to significantly change the cam specs. But then that leads into the relationship of CR and cam. These motors like cams and can be very street friendly and still make power to 7k. Most go with flat tops for bump in CR , but as mentioned you would have basically a ZX motor . The 79 head would have to be shaved to bump compression , but that’s not too $$. 

Don’t forget about gearing . Proper gearing with differential and trans can make for a fun , quick car with less power.

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After some more research I think I have a more clear idea on what I would like to do. ITMs (flat tops of course) with a 2mm head gasket and a 280ish cam. (Post #6 from http://forums.hybridz.org/topic/43671-n47-head-l28/) The thicker head gasket should keep the compression lower and hopefully keep the engine away from pinging. Thoughts on this build?

Here are the threads I pulled info from

http://forums.hybridz.org/topic/70335-n47-head-on-a-flat-top-l28/

http://forums.hybridz.org/topic/43671-n47-head-l28/

http://forums.hybridz.org/topic/85907-attn-flat-top-28-with-e31n42-head-guys/

http://forums.hybridz.org/topic/11398-raising-cr-on-l28-worth-the-effort/

Also I have read that when putting a new cam in you have to replace the rocker arms or else you'll annihilate your new investment. Is that true?

I would also like to mention that I have been toying with the idea of leaving the motor, for the most part, stock. Just lighten the flywheel a little bit, and, as Steve mentioned above, play with the gearing. This way I would have a little bit more money to put into suspension work where the z is really supposed to shine.

Edited by Rij Martin

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On ‎4‎/‎13‎/‎2018 at 5:41 PM, Diseazd said:

I like the torquey 3.1 liter, 7500 rpm screamer that goes “rumpety-rump!”   :beer:

 

Me too!! :D

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On ‎4‎/‎13‎/‎2018 at 8:53 AM, siteunseen said:

Good stuff here if you haven't already read it. :)

datsunzgarage.com, http://datsunzgarage.com/engine/

P79 head, http://datsunzgarage.com/p79/

Cylinder heads in general, http://datsunzgarage.com/heads/

Engine calculator, http://atlanticz.ca/zclub/techtips/calcs/engine builder/index.html

What happened to Bryan Little's site / Datsun Z Garage?  Can't access it any longer :(  Good thing I printed all the pages, have it somewhere in my mounds of junk.

Been a while since I've been here, but every so often, I get the bug.  I'd love a car that looks like Diseazd's (really all of his and father's - great 510 and some killer Z cars), but being on a budget a 3.1 stroker isn't in the cards.  Playing around with Z cars my entire driving age life (with some gaps in between, but always reading) tells me there's a lot to get from the mix / match route a la Bryan Little.

Digging deeper, I think a budget builder looking for a N/A L28 build could probably get away with leaving the lower parts / block alone.  So with the right carburetion and exhaust, I would think head work is where the focus should be (IIRC, the Honsowetz book spends a good amount of time on the head).

Sunbelt came and went - does anyone build a nice street performance head that is optimized for a stock lower end?

Edited by rdefabri

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http://www.rebelloracing.com/nissan1.htm

You'll need to call them to get a ballpark price.

After reading on here for quite a few years about frustrated buyers of heads off e-bay from California Datsun I would steer clear of him.  Al Allen is his name I think?

Somebody could have a good one on here.  @madkaw had one not too long ago.  maybe start a new thread, "looking for a complete cylinder head" or something similar.

Good luck.  Cliff

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My Rebello motor is an N42/N42 combo at roughly 3 liters.   Even 3 years ago neither Rebello or I were able to find a serviceable N42 head.  We sourced 5-6 of them but most were degraded past what could be used.  Luckily my car already had an N42/N42 setup so instead of swapping motors with a replacement he rebuilt what I had.

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11 minutes ago, Kurbycar32 said:

My Rebello motor is an N42/N42 combo at roughly 3 liters.   Even 3 years ago neither Rebello or I were able to find a serviceable N42 head.  We sourced 5-6 of them but most were degraded past what could be used.  Luckily my car already had an N42/N42 setup so instead of swapping motors with a replacement he rebuilt what I had.

Did you leave the dished pistons or go with flat tops?  I'm curious as to whether I can swap out my dished with some flats from a ZX motor and top it with an N42 head I am currently running without any problems from too much compression on pump gas.

Thanks for a reply.

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4 minutes ago, siteunseen said:

Did you leave the dished pistons or go with flat tops?  I'm curious as to whether I can swap out my dished with some flats from a ZX motor and top it with an N42 head I am currently running without any problems from too much compression on pump gas.

Thanks for a reply.

Is got 89mm Nissan KA24E pistons in it.  They appear to be "reversed dome" style dished pistons.  Also remember that here in California the highest octane fuel available is 91, and its got ethanol in it.  While I only use the best (garbage) gas available it runs fine in day to day usage.  I also told Dave that I prioritize daily driving over power so he may have chosen dished pistons to match that request.  This thing makes plenty of power without flat tops so I have no regrets.

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On 4/29/2018 at 11:20 PM, Rij Martin said:

I would also like to mention that I have been toying with the idea of leaving the motor, for the most part, stock. Just lighten the flywheel a little bit, and, as Steve mentioned above, play with the gearing. This way I would have a little bit more money to put into suspension work where the z is really supposed to shine.

I really like this idea as a Stage 1 kind of effort.  It might be satisfying enough, or it might be a gateway to pursue engine mods without wasting anything done in Stage 1.

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+1 for a lighter flywheel.  I have an aluminium one that is a lot of fun to drive.  Takes a minute to get used to it but that's it, then "vrooooooom, vrooooooooom!" like a street bike.

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45 minutes ago, siteunseen said:

+1 for a lighter flywheel.  I have an aluminium one that is a lot of fun to drive.  Takes a minute to get used to it but that's it, then "vrooooooom, vrooooooooom!" like a street bike.

+2 I also have one, a Fidanza mated to a centerforce.  I love it

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I guess this means the search for flywheels is on! Should I lighten my stock one or should I just go ahead and buy an aluminum one?

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