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1 hour ago, G8KeaPoR said:

So I have a U67 but have been contemplating a w53.  I’ve read a ton of info but which is better for power?  


In a previous post you talk about an L20B so keep the U67 head. The W53 is for a smaller L18 EFI engine sold only in Japan and the intake ports are smaller ..... 1.25" vs the U67's 1.375".

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So let me expand a bit.  I have a machine shop at home and by that I mean I have a brother Speedo s500x1 Vmc a 3 speed new way boring bar, crank polisher, 3 angle valve cutter, and even a piston nerlizer so making ports larger either by hand of by using the mill isn’t out of the question.  As mike said it’s probably better to stick with what I got and that makes the most sense financially and is what I am leaning towards.  But Given the two responses would it be even worth enlarging the ports just to have a peanut head or would it make more sense to port the u67 enlarge the valves and clearance them, polish the chamber and then run a semi domed pistons with valve clearances  on it to up the compression a bit.  I also plan to bore out the cylinders a bit to 88-88.5 mm. I have to ask jus because I don’t want to have any what ifs

this is all brainstorming of course.  The cheapest route is to go with the U67 head of course but I’m open to a little work in my off time over the winter for my machining business.  Essentially I’m taking a break from jobs since the boy was born so I have some free time.  The other option I’ve thought of was one of those dohc heads from I think a ka head but that seems to be overkill a bit.   I currently have dcoe 40’s that I am rebuilding for fuel and with be taking the time to deburing them as there are a few casting tabs they left in what I believe is the venturis. Carb really have never been my thing but doing EFI on and l series I might as well jus swap the motor which I really don’t want to do unless I got the sacrilegious route and drop in something non Nissan that I am more familiar with when it comes to tuning.


either way if I stick with the u67 I’ll be doing a valve job and possibly oversized as well as match porting the intake/exhaust being sure to leave the intake with a brushed finish for fuel/air mixture among other things.  We don’t have emissions where I live and with antique tags I can basically do what I want cost prohibited.   The only thing I haven’t figured is the cam shaft.  Any source info would be great for u67 cams since I’m leaning there.



Edited by G8KeaPoR
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The 280 zx pistons are 86mm or 1mm larger than the L20B and have no dish and are called flattops. These with a U67 will produce a 10.11 compression. Naturally the combustion chambers can be worked to remove shrouding around the valves and this will bring it down to a more reasonable level.


There are no L series pistons in 88 or 89mm size but a longer stroke Z22 crank in your L20B block bored to 89mm and your L20B rods fitted with 89mm KA24E flattops (actually 2.8cc) will produce a 2.3 liter 'stroker' engine with 9.78 compression. A 15% increase in displacement. It would be wiser to bore a Z22 block from 87mm to 89mm. Going from an 85mm L20B block to 89mm is a bit rash.

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The man has a machine shop, there are a lot of pros and cans there.


He is on the wrong side of the country to pick up parts easily, it would be better if you could find a Z22 block from a 1981/82 Datsun 720 or a Z22E block out of Datsun car of the same era, as even though the engine is tilted the other way in these vehicles the block is basically the same as an L20b block, all you have to do is put your U67/W53 head on that block after drilling 7 coolant holes in it to match the head.


What I did was bore the Z22 block out to 89mm and put stock Z24 pistons in it, then I had my W53 head port matched to my dual SU intake manifold(1.5"), I also had 280Z valves installed in the head with hardened seats, I used the stock cam because I need torque more than HP, I don't drive it like a race car, them pistons with the closed chamber W53 head put the compression ratio at 8.9 to 1, I also had to modify the distributor to burn regular gas, this engine is in my work truck, my truck and trailer weigh over 6000lbs together, I also have modern vented rotor front brakes, trailer brakes, and a 1986 Nissan dually axle in the rear, that engine would make a 510 move, maybe not like a VG30 but what Dmike and I described will bolt right into a 510 with all the L20b block stuff bolted onto the Z22 block.


Another thing to keep on mind is that it can be hard to find a good Z22 block, they get cracks between the center head bolt and the water jacket, my first one had 2 small cracks, I have not had an issue with them, but maybe I just got lucky.


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This is confusing you want to do all this but be cheap.. domed pistons?ect..... 

Matchport the W53head to 1.5 inch and your close to a SSS head. Closed chamber will raise the compression  instead by buying domed pistons for the L20.your done


do what you want but I seen to many flattop pistons in L20s w open chamber heads that need min 94 octane gas then can’t afford the gasoline,head gasket issues running cheap Felpro heasgaskets.

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The stock L20B piston has an 11.36cc dish in it and has an 8.4 compression. Flattop pistons alone reduces the combustion chamber by this amount and  makes 9.9 compression. If you get a custom made domed piston, say a conservative 5cc, the compression jumps to 10.8.


You can bore an L20B to 89mm but that's risky for wall thickness. A Z22 is already 87mm and the walls are naturally thicker for boring.


L20B bored to 89mm with custom* L series 11.36cc dish pistons.............. 9.052

Above with a flattop piston........................................................................... 10.65


* this won't be cheap


The recipe for the 2.3 is a Z22 block bored to fit KA24E pistons on a Z22 crank. You can use L20B or early and more common Z22 rods. (they are the same) Treat the Z22 block as an L20B just larger bore to begin with. Everything from the L20B... head, oil pan, timing chain, gears, cover, engine mounts.... fits the Z22 block. The increased bore and stroke would normally push the compression through the roof but the combination of rod length and pin height only allows the piston within 1.5mm below the deck height effectively making the combustion chamber larger and lowering the compression to a barely manageable 9.79 on an open chamber head. Here you would want to open up the combustion chambers to the max to unshroud the valves anyway so the compression would be dropped some.


A U67 would be the head of choice with it's already larger intake ports. Larger valve would actually help the breathing along with light port and polish.    


The increased stroke lowers the stock red line from 7K to 6.5K. Keep the stock L20B cam and increase the lift. This is not going to be a high RPM engine but a large displacement/stroke stump puller.

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My all time favorite engine combo is a long rod 2200. It is essentially a 89mm bore, L20B stroke with 6" Z20 (N85 casting) rods. It makes smooth power all the way up the power band and built on a budget, can run up to 7500 RPMs easy. With proper carbs, a lot of head work and a giant cam, they can make 230 HP and still be very streetable on pump gas. They can also be built on a budget and make 175 HP quite easily.


The reason I bring this up is because you say you have machine tools at your disposal. If you can do the work, then finding the correct rods, ordering a set of pistons and machining the block are the major keys to this puzzle. I will note that boring an L20B to 89mm is very risky, but can be done. Z20 and Z22 blocks lend themselves much better to this combo.


In my business, the one question that I always ask is - what are your expectations?


I follow that up with questions like - Do you want a stock idle and good mileage? Is spirited driving your style? Are you opposed to having to adjust the valves twice a year (regular street driving)? Do you have a budget?


Ask yourself all of these questions before you decide anything.

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7 hours ago, datzenmike said:

The stock L20B piston has an 11.36cc dish in it and has an 8.4 compression.

Flattop pistons alone reduces the combustion chamber by this amount and  makes 9.9 compression.

If you get a custom made domed piston, say a conservative 5cc, the compression jumps to 10.8.




If using a closed chamber head and a 5cc dish the compression jumps to 11.75.


Use the U67 head with maybe larger valves, from an L28,  hardened seats for longevity and a conservative cam, L28 flattop pistons for 9.9 to 1 compression and done. Run side drafts. 

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  • 1 month later...

Thanks for all the info and ideas.  So I have been busy with the year end and all and am just getting around to responding.  

Expectations:  To make more power so the car isn’t such a dog.  We don’t have emissions testing and because it’s on antique tags and pre ‘76 I can essentially do what I want with the car as there is no state inspection (cause of the tags) and so long as my lights work there isn’t much they can ticket me for.  The only stipulation is that it can’t be my daily driver which it never was going to be.   That leads me into the next bit.  I do t expect it to be as powerful as my rx7 or my late 911 but at least be fun.  As for fuel economy... well I got rid of my TDI a while ago for my daily which is a 3500 with a Cummins so I don’t mind dumping cash in fuel.  

What I mean when I say cheap:


I have plans in the future to possibly do a swap at the same time I do a full resto, but in the meantime I want to drive my car and since I had to pull apart the top end anyway I figure I might as well make it enjoyable until that time. I have the machining equipment so spending  a few grand in parts to hold me over until I am ready for the full resto In about two years is pretty cheap.   (Wife wants a boat and well happy wife and I can at least do what I want on the car.) who knows I may just keep the l in the long run if I can get the power needed to get the car out of its own way.  






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So from all the suggestions I decided to go with a long rod.  Unless I come across a z24 crank I’ll be doing a 2200.  Have an offer out on a z20s motor. If accepted I will bore it out.  If anyone is interested and in Virginia. I have a neway 3 speed boring bar with stand so once I have finished boring mine. I’d be happy to pay it forward within reason to the Ratsun community if anyone is in need.  

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Z24 crank throws won't fit the earlier L and Z blocks without trimming them and the block. If serious about a 2.4 liter engine, start with a Z24 truck engine. KA24E pistons fit in place of the 15cc dish and the compression is 11.3 with a better breathing L head will be much closer to a KA24E for power.... and at a glance it will look like an L series engine. 

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So I picked up a complete z20s motor.  For 450 and I’ll be prting out what I don’t need.  I know it’s got the shorter rods but are the heads worth anything off of it.  I know there is some emissions stuff on some of those motors but being it was a carburetor job...  other than that hopefully it’s got the right block for the long rod.  Thinking of just grabbing one of the n85 rods so I can make some billet ones on the mill.  I have a rod job coming up and I’m only going to make my own as I have a monster order for rods coming up that I can use this to figure out all the work holding etc on on mine rather then scrap materials through trial and error on a customer job.

Edited by G8KeaPoR
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The Z20 and the late L20B are within a hair of being the same blocks and they use exactly the same U60 crankshaft.



The Z20S was used in the '80-'81 A10. It had the N8500 6" or 152.5mm LONG rods.


The Z20E was used in the '80-'81 S110 200sx also with the N8500 LONG rods


If your Z20 has a head casting #W04 on it then it's from an '84-'86.5 720 Mileage option truck and has the N8500 LONG rods.


Did I mention that all Z20 engines use the LONG rods?



The Z series heads are worthless unless you have the W04 casting which has a smaller combustion chamber. Someone with an A10 or S110 who want's a 9 to 1 compression might want it. They were designed for high efficiency with low pollution at low RPMs and not for performance nor does it lend itself to being improved much..




Why would you re-invent the wheel when you have the better forged rods you want? 12100-N8500 at the dealer $100 each, if they still have some. Cheaper to buy up Z20s and pull them out.

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For some reason I thought the z20s had a different rod. Thanks for that. So long as they are in good shape I’ll just use them.  My thought process on making one of them was more or less to workout a work holding setup for when I make some rods for a customer but that can wait till later.


thanks for the info the plan is starting to take shape so I’ll keep you informed on the progress. 

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The L20B and the Z20 had the same crankshaft and basically the same block, bore and stroke. From crank center line to deck is 227.45mm so the L20B rod, 145.9mm and piston pin height 38.1mm plus half the stroke 43mm add to 227mm. For the Z20 the pin height was reduced and the rod length increased. 152.5mm + 31.75mm + 43mm = 227.25mm.


A Z20 engine with an L20B open chamber head becomes a long rod L20B and has a 10.18 compression

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  • 2 weeks later...

So I went and bought a few manifold gaskets so I could get a template for porting.  One of them is a Nissan one but here is the question.  Are there any templates out there for the porting? The reason I ask is normally I would just use the gasket but the ports on the 3 different brands of gaskets I got are all different sizes.   I’m inclined to use the Nissan one but two of the intake holes are ice cream cone shaped while the other two are standard round shaped on the gasket.  Oh and I have both a u67 square port and an a87 head   I know earlier I mentioned getting a w53 but I happened across an a87 head for next to nothing so I grabbed it.  

Edited by G8KeaPoR
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