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TheCrazySwede

Building an L28 (NA)

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UPDATE: 2/14/15

 

After a rather long hiatus, the build returns with updates! As some of you may know, I decided to go with the professionals with this build. 

Looking at some local shops around my area, most notably Rebello Racing, and also some other shops across the country, I've decided to send my dear L28 out to Eiji Hosomi at Datsun Spirit Inc. (https://datsunspirit.com/)

 

There are three main goals that I wanted my motor to achieve.

1. Speed > Power. I want my motor to run like a hot knife through butter. It needs to be quick and very responsive. Power is nice, but a quick revving motor is what I seek.

 

2. Character. My beloved Z will eventually be my weekend car. I don't want the motor inside of it to just be a fast engine. It needs personality and character. Something that sets it apart from, let's say, a Honda Civic. This is why I went for triple Weber 45's, a flywheel that weights less than 10lbs, and my desired cam (more info on those later.) There's a certain character I want this motor to display, and I believe this build fits the bill just right.

 

3. Reliability. It might seem like an oxymoron, having a fast and reliable sports car motor, but I've seen time and time again how these motors, when built by true artists of their trade, can withstand almost anything you throw at them. My new motor will be running on pump gas, will idle smoothly and will barely break a sweat with the granny-like driving I put my Z through.

 

 

Engine Specs:

Bore/Stroke: 89mm/79mm

Pistons:  29mm Kameari (280g)

Rods: 139.5mm Kameari (~575g)

Crankshaft: Polished, Stock L28

Camshaft: .290 Duration / .490 Lift

Valves: New valves (stock size) Upgraded springs and retainers

CR: ~10.5 to 11:1

 

Now, time for some photographs!

 

Here's an album with all the photos I've gotten from Eiji thus far. I'll update it as the build continues:

http://imgur.com/a/Fyqtv

 
 
 
 
ORIGINAL POST:
 
Dear Forums,
 
I've been a long time lurker of these forums (along with Classic Z Cars) and of the community, but just recently, I've decided it was time I popped my Z cherry and got involved. I own a '77 280z (Motor has EFI; Transmission has 4 Gears)
 
I'm currently working on another L28 that I picked up (Carbed, N42 Head)) along with a 5-Speed, but due to my lack of knowledge regarding these motors (We are a family of Ford Mustang owners) I seek your help in order to make sure this build isn't a total disaster.
 
To start off, hello; My name is Mike :)
I am 20 years old and I'm a computer tech. This is my first engine rebuild, so experience is not really something I have in my corner. Luckily, my brother and my dad are both mechanics, but they decided to pretty much leave me to learn how to swim in the ocean with this build. 
 
My goals for this motor are pretty simple and straight forward, but I would still love to get some help from some of you more knowledgeable L-Series petrol heads.
Let me start by saying that I am not power hungry. We have the pony cars for that. What I want is a responsive motor, not a powerful one.
 
Engine Goals (Might get redefined as I learn more about these L-series motors)

1. I would like to hit 200HP at the crank (Although not necessary)
2. I want the motor to be naturally aspirated.
3. I love the look and sound of triple Weber carbs.
4. I don't think I need a stroker motor to produce a descent amount of power, so unless it's necessary, I'd rather not go there.

Things that I am considering (Please correct me if I'm wrong!)

1. Balancing the Crank
2. Lighter, flat-top pistons (I would like to keep the stock 86mm size)
3. Stock valves look good enough! Probably just stay with those.
4. I've read a few posts where people mentioned using L24 rods. Why is that? Weight?
5. A Mild performance Cam with upgraded springs.

 
As I mentioned above, I'm just learning about these motors, so your help is very much appreciated. I'm gonna need all the knowledge I can get. 
 
This is the motor:
 
So it started with this
 
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5M79mrsl.jpg
 
MZfwDCYl.jpg
 
rRz9H0el.jpg
 
 
Time to clean!
 
lFsPmOPl.jpg
 
VkHbanfl.jpg
 
6nSrTsml.jpg
 
XdhA8eml.jpg
 
 
So that's pretty much it so far. Cheers guys, and thanks a lot for the help!
Not that it matters much, but here is the car:
 
292p6cm.jpg
Edited by TheCrazySwede

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I'd skip the schneider cam and get something bigger, but that's just me. Look into Delta cams regrinds or Isky regrinds, and don't count on your lash pads being a certain size till you have the cam and your refinished rockers in hand, and the valve job has been done.

 

Look for a cam with a 64-68 degree intake closing point, if you are going to run flat top pistons and an N42 chamber. it will help with any possible detonation issues you might have.

 

If running carbs, the stock SU carbs can be quite nice if they are in very good condition, if not, then triple Mikuni PHH44s are very responsive, as are Weber DCOE45s. both will need to be tuned appropriately but will reward you with snappy throttle response and a harmonious sound.

 

Look for a header with 1 5/8 primary tubes, with your final merge 28 to 36 inches from the back of the valve. Be sure to fit an M18x1.5 threaded bung in there after the final merge, just plug it if you need, but it will be needed if you want to run a wideband O2 sensor to assist on your tuning.

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I'd skip the schneider cam and get something bigger, but that's just me. Look into Delta cams regrinds or Isky regrinds, and don't count on your lash pads being a certain size till you have the cam and your refinished rockers in hand, and the valve job has been done.

 

Look for a cam with a 64-68 degree intake closing point, if you are going to run flat top pistons and an N42 chamber. it will help with any possible detonation issues you might have.

 

If running carbs, the stock SU carbs can be quite nice if they are in very good condition, if not, then triple Mikuni PHH44s are very responsive, as are Weber DCOE45s. both will need to be tuned appropriately but will reward you with snappy throttle response and a harmonious sound.

 

Look for a header with 1 5/8 primary tubes, with your final merge 28 to 36 inches from the back of the valve. Be sure to fit an M18x1.5 threaded bung in there after the final merge, just plug it if you need, but it will be needed if you want to run a wideband O2 sensor to assist on your tuning.

 

After reading up on Cams, I'm probably better off with an Isky cam, like you mentioned. Their State III Cam sounds very intriguing!

There's a shop near where I live that have experience tuning Weber Carbs, so that'll definitely help a lot.

 

Any tips on pistons? What type of flat top options would i have if I didn't want to bore the head? (86mm) 

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If running carbs, the stock SU carbs can be quite nice if they are in very good condition, if not, then triple Mikuni PHH44s are very responsive, as are Weber DCOE45s.

Although I don't have nearly as much experience as you, I'm under the impression that Weber 45s would really be much more than he needs, and probably not as street friendly as 40s. He's only looking for 200hp. I have 40s and I feel that would be a better choice. Correct me if I'm wrong.

 

9mm L24 rods are generally used with an LD28 crank in a stroker.

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40's are too small for an L28...they're only just big enough for an L24, really.

 

Any L on 40's will make more power with little to absolutely no difference in drivability with 45's, assuming both are properly tuned and the choke sizes are correct.

 

ITB throttles should be approximately 80% the size of a single throttle plate for a given engine, and engines that breath well can use throttles up to 95%.

 

Either way, they'll work...just one will make more power than the other for little to no difference in cost or drivability.

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Thank you, gentlemen, for both of your inputs!

 

I still have a bit more research to do before I go purchasing parts and start swapping things around. 

I contacted Rob Fuller of Z Car Garage, and he also recommended the 45's for the L28.

 

I wanted the car to be responsive and snappy. Power figures isn't my top priority.

 

I know properly tuned Weber's, Valvetrain (Cam, springs, etc.) and a lightweight flywheel will already get a more responsive motor, but I was wondering if there were any more swaps I should do. I am now dealing with an empty block, so I suppose I build the engine back up with a setup I'm more satisfied with. I would prefer to keep the bore the same (86mm), but I don't know if I can get lighter, flat-top pistons at that size. The L24 crank and rod setup is something that seems interesting, but I am kind of confused regarding the size and positioning of things....wouldn't the setup cause a much lower compression ratio?

 

If boring it to 87mm and going with the flat-top ZX pistons (or even the 240sx ones) is the better way to go, I'll go that route. I just want a responsive motor that isn't afraid climb, rather than a powerhouse. 

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The larger the piston diameter, the better...to a point. It allows better valve motion and unshrouding, allows a lower cylinder pressure to exert the same force, but at the same time becomes more detonation prone...all of this is generalization but you get the idea of what you're balancing here.

 

With no headwork at all, an 87mm bore does well. 86mm does just fine too, but once you get to 88mm and beyond you're really just spending money if you're not starting to pull in the chamber shape and valve placement into the picture.

 

The L24 rods on the diesel crank are used to make a commonly available piston workable...the difference in rod/stroke and bore/rod ratios aren't world-shifting, so unless you've already planned on and aquired the right parts, don't worry about it.

 

If you're not doing any port or chamber work, going over 0.460" lift isn't really beneficial, IMO. Exceeding 280* of seat duration tends to make things soggy under about 2000RPM, but from 2500-6500 most cams of that spec will rev nicely.

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So, I gave Rebello a call (Turns out they are about an 1 hour away from where I live!)

I asked him what type of pistons he recommends. He said he hasn't faced many issues with the flat-tops in the N42 head, but if a higher compression isn't needed, he would recommend the dished ones. I also asked him about valvetrain improvements, and he recommended a mild cam with a rather low lift (about .448) but he said that the Cam produces great torque and works great for street use. He said that Z Car Garage (Another highly rated Z specialty team) prefers that Cam Kit over most, mainly due to its power delivery. 

I'm going to go over to Rebello (bring my head!) later this week, probably on Thursday, and see what can be done. They use ITM Pistons, by the way.

 

Thanks a lot, gentlemen, for your help! I'll report back with what we talked about.

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I was going to suggest calling Robello. He has many custom cam grinds that work excellent on a Z. He typically does not give out the specifications as he keeps the secrets under wraps. However, if you describe what you want Dave can provide it. I run one of his cams on my 3.1 L  it has power everywhere. This cam may be more than what you are looking for but if you are interested you can ask him about the cams he has been selling to Steve Pettersen of Pettersen Motorworks in Chico Ca.

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hey guys im in the proccess of building a l28 too.im planning on using it for the street

 

i was thinking 

crankshaft balanced

274F Datsun L-6 Camshaft

n42 port and polished 

sk triple 40 bought them 

Valve 46 intake

Valve 38 exhuast

flat top

arp mian stud

rods arp

8000rpm valve

 

goal close to 200hp 

 

what do you guys think and what do you suggest thanks

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hey guys im in the proccess of building a l28 too.im planning on using it for the street

 

i was thinking 

crankshaft balanced

274F Datsun L-6 Camshaft

n42 port and polished 

sk triple 40 bought them 

Valve 46 intake

Valve 38 exhuast

flat top

arp mian stud

rods arp

8000rpm valve

 

goal close to 200hp 

 

what do you guys think and what do you suggest thanks

Make your own thread. Don't high jack his. I'm paying attention to this thread so don't screw things up.

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I would not spend any money on an over bore unless the block needs it. Spend your money on the head and cam. 200hp is easily attainable with stock dished pistons - with a good build you can hit almost 200hp in an L28 with the stock head, cam and SUs.

 

Partts are easy. The horsepower is in the machining, assembly, and tuning.

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I would not spend any money on an over bore unless the block needs it. Spend your money on the head and cam. 200hp is easily attainable with stock dished pistons - with a good build you can hit almost 200hp in an L28 with the stock head, cam and SUs.

 

Partts are easy. The horsepower is in the machining, assembly, and tuning.

 

That's the conclusion I reached, too.

 

I sent the block, crank w/ rods to a machine shop to get it checked out first. I bought the motor from someone on CL, and he didn't know much about the engine, himself. Just want to make sure the block is in good condition, and also what size bearings I'll need, and such. As I've mentioned before, I'm not really power hungry, but I would like a responsive motor, not a sluggish one. Working on the valvetrain and a lighter flywheel will already give me that, so I'm already set, so to speak. I already have a set of rebuilt SU Carbs and competition headers (6-2), so for now, I'm just taking pre-cautions to make sure the motor is built right. Proper balancing is also high on my priority list. All that mass adds up!

 

Thanks for all the help guys! I'm hoping the machine shop gets back to me at the beginning of next week. Once I get the info back from them, and hopefully all the components are in good shape, I'll head north towards Rebello to see how we can build a nice head.

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So, just got a callback from the machine shop.

 

My crank is healthy, just needs a polish. Stock size bearings will do.

However, the block needs to be bored. As of now, I'm just looking around and seeing what type of pistons I should get, and just bore it to fit those measurements.

 

I've heard people using the pistons from a 240sx and some people even using the 370 ones (They look massive when compared to the stock ones.)

I'm still looking around, but are there any fan favorites I should know about? 

 

Thanks lads!

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The 240sx pistons have a much shallower pin height and are usually used with longer 240z con rods.  Looks like the 370z is at 95mm (!), that would take a lot of machining...

I'm having mine built right now with ITM +1mm flat tops.

 

Oh shoot, 95mm! I must've misread what car it was from, but I think the ones I saw were 89mm. 

The ITM pistons look nice! As far as piston sizes go, is bigger always better? Aren't the bigger ones more heavy, thus increasing the mass?

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What are you having done with your head?  

 

I would look into a P79, P90 (both at 53.6 CC combustion chamber) or MN47 (a maxima N47 which has about a 40cc combustion chamber) as they have a much better closed combustion chamber that resembles SBC aftermarket heads and many people feel work better with flat top set ups.  

 

I run an MN47 on my bone stock L28 F54 flat top set up  which produces about 11.5:1 compression!  yeah, its high, but it also produces a LOT of torque because of the compression ratio but also because the MN47 has 42mm intake valves as opposed to 45mm on the L28 stuff.  LOTS of velocity.  

 

I have not installed an aftermarket cam on this yet, and I do have to pull a bit of timing, but I am running megasquirt controlling fuel and spark, so my situation is a bit different than running carbs and a regular distributor.  I feel an aftermarket cam with more duration could be the hot ticket with this set-up.  

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