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L20B big bore with low end torque


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  • 4 months later...
12 hours ago, JumboFett said:

Hi! Anyone know if these L20B / Z22 crank combos are covered in the “How to Modify Your Nissan Datsun OHC Engine” book?

Taking a look... discusses the bore/stroke combinations, and the Z22 components specs (block, pistons, crank, connect rods, etc.) are listed in spec tables throughout. And mentioned with part considerations - e.g. counterbalanced, bolt holes,  journal sizes, etc.

 

But there's no 'How to assemble a badass LZ' section.

PXL_20221204_174857400_3.jpg

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I don't think so. These were mostly developed after the books were written.

 

If you can get your hands on a set of N85 rods from a Z20, you can build a "2300". This motor uses the Z22 crank and an 89mm bore. The long rods improve the power curve and smooth out the balance in the upper RPM ranges. You can use an L20B block, but 89mm in that block means going .120" over, leaving the cylinder walls pretty thin, though it's been done many times. Preferable to the L20B block is the Z20 block, which has thicker cylinder walls and can take .120" bore easily. The Z22 block can also be used, but it has steam ports between the 1-2 and 3-4 cylinders which can be accidentally cut into. You can have the machine shop "spread" the bores out from those 1-2 and 3-4 centerlines to avoid cutting into the steam ports.

 

Any of these combos requires a custom piston, but it has come to light recently that there is an off the shelf piston that works. I can't remember if it is Mitsubishi or Chevy 4cyl. Someone here might know. Custom forged pistons cost about $800-$1000 and take a month or more to get made, but it's worth it.

 

Here are four of these motors. Two I built while I was working for Rebello, two were built by Rebello in the years since. They are all in friend and family cars, and all run very well, making between 210 and 240hp.

 

Painter_Man_2300_Small_033_zpsih8qrkkm.j

 

Trevor_510_Small_022_zpsuaebw7of.jpg?wid

 

IMG_3084Small.jpg?width=960&height=720&f

 

IMG_0572Small.jpg?width=960&height=720&f

Edited by Stoffregen Motorsports
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 You would need a piston with with a 28.95mm pin height. (or less) 28.95 - 20.99/2= 10.495mm is 18.455mm or 0.727" between the pin top and the top of the piston for piston rings. Those buttons in the pin holes would be needed to keep the top ring down away from the piston tops.

 

If flattop custom pistons, that's an 11.86 compression so a nice big dish will be needed.

 

A cheaper easier alternative is the original big bore 2300: L20B/Z22 rods and KA24E pistons in an 89mm bored L20B/Z20 Z22 block, for 9.78.

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  • 2 weeks later...
On 12/4/2022 at 10:16 AM, Stoffregen Motorsports said:

I don't think so. These were mostly developed after the books were written.

 

If you can get your hands on a set of N85 rods from a Z20, you can build a "2300". This motor uses the Z22 crank and an 89mm bore. The long rods improve the power curve and smooth out the balance in the upper RPM ranges. You can use an L20B block, but 89mm in that block means going .120" over, leaving the cylinder walls pretty thin, though it's been done many times. Preferable to the L20B block is the Z20 block, which has thicker cylinder walls and can take .120" bore easily. The Z22 block can also be used, but it has steam ports between the 1-2 and 3-4 cylinders which can be accidentally cut into. You can have the machine shop "spread" the bores out from those 1-2 and 3-4 centerlines to avoid cutting into the steam ports.

 

Any of these combos requires a custom piston, but it has come to light recently that there is an off the shelf piston that works. I can't remember if it is Mitsubishi or Chevy 4cyl. Someone here might know. Custom forged pistons cost about $800-$1000 and take a month or more to get made, but it's worth it.

 

Here are four of these motors. Two I built while I was working for Rebello, two were built by Rebello in the years since. They are all in friend and family cars, and all run very well, making between 210 and 240hp.

 

On 12/4/2022 at 10:57 AM, datzenmike said:

 You would need a piston with with a 28.95mm pin height. (or less) 28.95 - 20.99/2= 10.495mm is 18.455mm or 0.727" between the pin top and the top of the piston for piston rings. Those buttons in the pin holes would be needed to keep the top ring down away from the piston tops.

 

If flattop custom pistons, that's an 11.86 compression so a nice big dish will be needed.

 

A cheaper easier alternative is the original big bore 2300: L20B/Z22 rods and KA24E pistons in an 89mm bored L20B/Z20 Z22 block, for 9.78.

 

I’ve been thinking about your responses for a week wracking my brain over the possibilities! Were those 210-240hp engines for the street or were they purely race? I’m guessing they used side draft carbs or some kind of fuel injection; could you get close with a Sniper EFI? Would keeping the bore down to 88mm make for more reliability or would it defeat the whole purpose? (I have a L20B) What about a turbocharged combo? 
 

I could keep going… thank you in advance.

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210 hp+ is well over doubling of power for the L20B so race. They would not be street friendly.

 

The KA pistons for the 2300 are 89mm. There would be no 88mm size. Going smaller by 1mm makes almost zero difference. The engine is smaller by only a little over 3cc per cylinder.

 

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10 hours ago, JumboFett said:

 

 

I’ve been thinking about your responses for a week wracking my brain over the possibilities! Were those 210-240hp engines for the street or were they purely race? I’m guessing they used side draft carbs or some kind of fuel injection; could you get close with a Sniper EFI? Would keeping the bore down to 88mm make for more reliability or would it defeat the whole purpose? (I have a L20B) What about a turbocharged combo? 
 

I could keep going… thank you in advance.

Those engines are street engines built to run on pump gas. They were all built with reliability in mind and tuning them is not overly difficult. They do require occasional valvetrain maintenance, especially if you like to run them up into the higher RPM range.

 

Yes, they all use dual side draft carbs, 44mm Mikunis. You could run 45 DCOE Webers, as they are easier to find. The Sniper system would limit the HP, mainly because of the shape of the manifold. Even if you ran a 4bbl EFI system, the hard 90 degree turn would hurt performance. Best results from EFI would be from the side draft EFI throttle bodies. Jenvey makes them to look nearly identical to Weber DCOE carbs, but they are expensive at over $600 each, and that's without a manifold.

 

You could use an 88mm piston, but you would still have to use custom pistons for the correct pin height and compression volume.

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6 hours ago, Stoffregen Motorsports said:

Those engines are street engines built to run on pump gas. They were all built with reliability in mind and tuning them is not overly difficult. They do require occasional valvetrain maintenance, especially if you like to run them up into the higher RPM range.

 

Yes, they all use dual side draft carbs, 44mm Mikunis. You could run 45 DCOE Webers, as they are easier to find. The Sniper system would limit the HP, mainly because of the shape of the manifold. Even if you ran a 4bbl EFI system, the hard 90 degree turn would hurt performance. Best results from EFI would be from the side draft EFI throttle bodies. Jenvey makes them to look nearly identical to Weber DCOE carbs, but they are expensive at over $600 each, and that's without a manifold.

 

You could use an 88mm piston, but you would still have to use custom pistons for the correct pin height and compression volume.

There will come a time where I will pick your brain for even more details on that build. I’m currently in a position where I don’t live in a house with a garage, so I’m limited to top end stuff. But we are in the market to buy, and when I am able to pull an engine in my own garage a 200+hp NA L4 will be my first project. 
 

Y’all have been so incredibly helpful it blows my mind. Thank you 🙏 

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On 12/12/2022 at 9:34 PM, datzenmike said:

210 hp+ is well over doubling of power for the L20B so race. They would not be street friendly.

 

The KA pistons for the 2300 are 89mm. There would be no 88mm size. Going smaller by 1mm makes almost zero difference. The engine is smaller by only a little over 3cc per cylinder.

 

 

On 12/14/2022 at 7:41 AM, Stoffregen Motorsports said:

Absolutely. Let me know when you're ready.

 

22 hours ago, Colbino said:

I have nos n85 rods if you need a set.

 

I'm currently building the 2.1 liter long rod with oversized 87mm vg30 flat tops.

Am I ok to give Colbino a link to my Instagram or is that against forum policy? 

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55 minutes ago, datzenmike said:

Thank you! I didn’t realize each profile had its own dm feature. I guess I’m still a bit new.

 

Re my IG link, I wouldn’t mind posting it, It’s all Datsun stuff anyway.

https://www.instagram.com/p/ClrDS5cJ3yB/?igshid=YmMyMTA2M2Y=

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  • 3 weeks later...
On 12/4/2022 at 10:57 AM, datzenmike said:

 You would need a piston with with a 28.95mm pin height. (or less) 28.95 - 20.99/2= 10.495mm is 18.455mm or 0.727" between the pin top and the top of the piston for piston rings. Those buttons in the pin holes would be needed to keep the top ring down away from the piston tops.

 

If flattop custom pistons, that's an 11.86 compression so a nice big dish will be needed.

 

A cheaper easier alternative is the original big bore 2300: L20B/Z22 rods and KA24E pistons in an 89mm bored L20B/Z20 Z22 block, for 9.78.

Is that 9.78:1 with a closed or open chamber head?

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