Jump to content


Photo

Rebuilding my L20B


  • Please log in to reply
237 replies to this topic

#1 ErickwithnoK

ErickwithnoK

    Advanced Member

  • Members
  • PipPipPip
  • 192 posts
  • Location:Oregon
  • Cars:620

Posted 28 April 2017 - 03:29 PM

Hello everybody. Here is some pictures to make you care about my project.

 

[/URL]">http://20170308_104229_zpsumirpcov.jpg

[/URL]">http://20170323_150715_zpspsfbtewx.jpg

[/URL]">http://20170310_122020_zpsvwiwezfc.jpg

[/URL]">http://20170310_112858_zpslb0d02rk.jpg

 

I recently spent a lot of time de-smogging my 76 620. It now has a smogless cast manifold from a 521, and an intake manifold from an l16 of unknown origin that is also smogless. While I was taking everything apart I did a lot of cleaning up, during which I uncovered a couple of oil leaks. I've got oil coming from the front of the block (looking like head gasket) as well as out of the spark plug on cylinder #2 (piston rings not sealing?). I don't need to daily my truck at the moment, and I want to do a rebuild to remedy these issues and as a fun project. It will be the first time I've taken the head off a motor, and I'm super excited about the project. 

 

I know that there are rebuild threads, and even threads for the 2.3 l20 that I would like to do, I have read them and will read them again as I go through my build.  I would still like to ask some specific questions about the process because I'm not familiar with the process, as well as have a thread open ahead of time because I will definitely have questions when I get started.

 

My goals for my build may be far fetched for my budget, but you tell me. I would like to do the following with my rebuild:

 

1. Keep my block and head. I have a U67 head on an l20b block and I would like to keep them to save the expense. (Will modify where necessary!)

 

2. Run sidedrafts. I would be open to dcoe's or mikuni's but am leaning towards the webers for cost effectiveness. 

 

3. 2.3 liter. z24 crank and Z pistons (if I'm remembering right) 

 

4. Electronic distributor

 

5. Actually enjoy the project, and not spend over 2k on the above modifications

 

6. Drive it to Canby  :thumbup:

 

That leaves me with a lot of questions. 

 

1. Is the U67 head well suited for this application? Will I be able to modify my block at home with a moderate amount of tools? What local shops (I'm from the Scappoose area in Oregon) would you guys recommend I go to for a hot tank, crankshaft adjusting, cylinder boring, head resurfacing....all the stuff I can't do in my garage, and what is a roundabout figure for these things? 

 

2. Will I need an electronic fuel pump to feed my sidedrafts (probably dcoe 40's or 45's jetted for my 2.3)? I have a cast manifold, will headers give me significant power gains with these modifications? Is my new 2-1/4 exhaust big enough to not restrict a 2.3l? Is my brake booster really a clearance issue? 

 

3. Valve train? Do I need bigger valves?

 

4. Are my goals unreasonable? Should I stick with a simple rebuild? If 2k isn't enough cash, what can I do within my budget?

 

I have 3 books I'm currently reading to get my primed for this project: How to rebuild your datsun OHC engine, How to modify your datsun OHC engine, and a Nissan service manual for my 1976 620. Other resources include a shop space to park my truck while I work on it, a moderate amount of tools (no cherry picker or stand yet), and help from a very smart and generous dad. I'll be working on this week nights and most Saturday/Sunday afternoons till it's done. 

 

I love my truck and I get excited every time I think about what it could be with these changes. Thanks ahead of time for all the help, I'll post pictures along the way to keep you involved and excited about my project.



#2 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,285 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 28 April 2017 - 04:19 PM

1/ Up to $1,500 but depends how much you do.

 

2/ Weld up your own intake and run R-1 Yamaha bike carbs.

 

3/ Z24 crank does not fit the L20B block. If you want 2.4 liters rebuild a Z24 and put your U67 head on it. A Z22 crank with L20B rods and KA pistons makes a nice LZ 2.3. It'll take 5 weeks just to find a Z22 crank.

 

4/ Yes!

 

5/ Yes. See 1/ above

 

6/ You have about 5 weeks to do this. Do it after Canby.

 

 

 

1/ The U67 is a fine head. If over boring the block, you will need over size pistons and rings, rod and main bearings and a gasket set.

 

2/ Probably not. The L20B can only run a certain amount of air through it. Multiple carbs do not automatically use twice as much fuel.  Your cast iron header has more than enough flow. Save your money.

 

3/ If totally rebuilding your head you could go larger valves and seats. I wouldn't bother unless changing the cam and doing some porting.

 

4/ I would stick to a simple rebuild. Make it brand new and strong, then if later you want to add something like a cam or multiple carbs you have a good base to start with.


Posted Image

#3 KELMO

KELMO

    Senior Member

  • Senior Member
  • PipPipPipPip
  • 1,920 posts
  • Location:Edgewood NM
  • Cars:71 Goon, 72 1200 coupe x 2, 69 F250

Posted 28 April 2017 - 04:33 PM

OK, so I really didn't read your post.....I just looked at the oics.  I'll be back, I promise cuz I am fixin to do an L16.


NISMO: Nissan Impresses Sluts More Often
"Well, primer gray IS a color..." (quote: Kelmo's wife)

#4 Draker

Draker

    Ratsun-Erect

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 12,709 posts
  • Location:Eugene, Or
  • Cars:1971 2 door 510, 1969 4 door 510, 2002 Tacoma double cab

Posted 28 April 2017 - 05:20 PM

Just rebuild the L20.. don't go crazy with it. You'll be swapping it out for something else in a few years if you keep the truck.


View my 69 510 4dr Sedan - Build Thread
View my 71 510 2dr Sedan - Coming soon.

http://drakers.pl510.info

 

 


#5 ErickwithnoK

ErickwithnoK

    Advanced Member

  • Members
  • PipPipPip
  • 192 posts
  • Location:Oregon
  • Cars:620

Posted 28 April 2017 - 06:11 PM

1/ Up to $1,500 but depends how much you do.

 

2/ Weld up your own intake and run R-1 Yamaha bike carbs.

 

3/ Z24 crank does not fit the L20B block. If you want 2.4 liters rebuild a Z24 and put your U67 head on it. A Z22 crank with L20B rods and KA pistons makes a nice LZ 2.3. It'll take 5 weeks just to find a Z22 crank.

 

4/ Yes!

 

5/ Yes. See 1/ above

 

6/ You have about 5 weeks to do this. Do it after Canby.

 

 

 

1/ The U67 is a fine head. If over boring the block, you will need over size pistons and rings, rod and main bearings and a gasket set.

 

2/ Probably not. The L20B can only run a certain amount of air through it. Multiple carbs do not automatically use twice as much fuel.  Your cast iron header has more than enough flow. Save your money.

 

3/ If totally rebuilding your head you could go larger valves and seats. I wouldn't bother unless changing the cam and doing some porting.

 

4/ I would stick to a simple rebuild. Make it brand new and strong, then if later you want to add something like a cam or multiple carbs you have a good base to start with.

 

Just rebuild the L20.. don't go crazy with it. You'll be swapping it out for something else in a few years if you keep the truck.

 

Honestly I think the r1 carbs would be a really fun project. I've seen videos of l20's with r1 carbs and they sound amazing. Also, the info about the z22 crank is great stuff. Have I heard of people grinding down z24 crankshafts to make them fit the l20 block? Does the z22 crank fit an l20 block without modification? 

 

Thanks for the honest replies. I should probably just do a basic rebuild. I will definitely be going a new route in terms of carbs, because I currently have a hitachi that is just not fun to work on. I know I could probably get it to work great and have good fuel economy and stock power, but honestly I want something more exciting than the hitachi or a 32/36. Side drafts are what I want, so dang it that's what I'm doing. R1 carbs count as side drafts right?

 

If I went to 40dcoe's on a stock l20 or r1 carbs on a stock l20, would I recieve any power gains? Or is a stock carb pushing all the air and fuel my motor can handle?

 

I have 5 weeks before canby and I should probably just collect parts until then, or wait until after canby to see if I can buy anything interesting there...thanks for the advice. 

 

Not sure if I'll ever want to swap anything into it in any amount of years. What drew me to datsun's was the l series motors, their simplicity and sound, and the fact that I can look at it and know a thing or two about how it works. No KA24 or SR20's for this datsun.



#6 wayno

wayno

    Datsunahaulic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 12,980 posts

Posted 28 April 2017 - 06:34 PM

I have a 2.3 in my work truck, I used a Z22 block, crank, and rods, I had the block bored out to use stock Z24 pistons, and I used one of my modified W53 closed chamber L heads with large valves installed, the intakes were port matched to my dual SU manifold.

Your U67 head already has large valves and intake ports, so just rebuild the head if it needs rebuilt, boring out an L20b to except large pistons is a crap shoot, how big are Z pistons, I definitely would not bore an L20b out to 89mm. 

I would keep it simple the first one, I would fix the block if possible and collect the parts needed for a 2.3, then build it on the side taking your time, then install it over a weekend, that is a win/win in my world.


 

 


#7 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,285 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 28 April 2017 - 06:47 PM

R-1 carbs are side draft.

 

Not a huge gain but when paired with a 'larger' cam it has more potential. The engine block is built for strength. The head is where all the power is made. 


Posted Image

#8 ErickwithnoK

ErickwithnoK

    Advanced Member

  • Members
  • PipPipPip
  • 192 posts
  • Location:Oregon
  • Cars:620

Posted 28 April 2017 - 07:08 PM

I have a 2.3 in my work truck, I used a Z22 block, crank, and rods, I had the block bored out to use stock Z24 pistons, and I used one of my modified W53 closed chamber L heads with large valves installed, the intakes were port matched to my dual SU manifold.

Your U67 head already has large valves and intake ports, so just rebuild the head if it needs rebuilt, boring out an L20b to except large pistons is a crap shoot, how big are Z pistons, I definitely would not bore an L20b out to 89mm. 

I would keep it simple the first one, I would fix the block if possible and collect the parts needed for a 2.3, then build it on the side taking your time, then install it over a weekend, that is a win/win in my world.

 

What does a z22 come out of? I will be wanting to keep my eyes peeled for an opportunity to snatch up those parts. Great advice, thanks.

 

 

R-1 carbs are side draft.

 

Not a huge gain but when paired with a 'larger' cam it has more potential. The engine block is built for strength. The head is where all the power is made. 

 

R-1 carbs are very tempting. Is it something you've done before, Mike? Not sure about my welding skills but it would be a super fun project and a great learning experience. Then I'd have something unique  B)

 

What do you mean by larger cam? Is it a camshaft from another motor or something custom? 

 

If the engine block is built for strength, would my stock block handle a modified head without issue?



#9 wayno

wayno

    Datsunahaulic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 12,980 posts

Posted 28 April 2017 - 07:37 PM

The 1981/1982 Datsun 720 came with the Z22 block, it makes for a torky LZ23 that will pull away from a Z24, at least mine does.


 

 


#10 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,285 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 28 April 2017 - 07:39 PM

I have a set and working on an intake. Slowly getting there. There is a good read about them... http://community.rat...s-lots-of-pics/

 

A 'larger' cam has more lift (holds the valve open farther) and duration (holds them open longer) It's all about breathing air. The more air you can get into an engine and out again the more power it makes. Keep in mind the the higher you rev the engine the more power you make too. On the flip side, too large a cam makes the engine less fun to drive at idle and low speeds. For a 'larger' cam you will have to go after market, probably have your stock cam reground. Don't go overboard. Better to have too 'small' a cam and want more, than to have too big a cam and wish you had smaller.

 

Any good block rebuild to stock specifications will handle any head mods you might do.

 

 

The Z22 engine was used in the '81-'82 720 truck and the '81-'83 S110 200sx.

 

 

As to cutting the Z24 crank down yes but with a lot of bother. There is a reason the Z24 block is taller... it's to complement the longer stroke. Stuffing a long stroke crank into a shorter block isn't the best idea.


Posted Image

#11 flatcat19

flatcat19

    Back in Black

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 19,943 posts
  • Location:Tri-Cities, WA/PDX
  • Cars:Smaller. Better. Slower. Lower.

Posted 28 April 2017 - 07:44 PM

Ask anyone with a L/LZ22 what that gas mileage is.


Last LZ23 I saw got around 8-10 mpg.
The LZ22 I had went though a tank in a couple of hours.

No need to go all out. A moderate L20B build will net you a quick whip.


Cheap, fast, reliable. Pick 2.

You can't hang if your nuts haven't dropped...it's physics


#12 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,285 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 28 April 2017 - 07:49 PM

A 10% increase in displacement shouldn't drop the mileage.... that much. Maybe in a truck with 4.357 gears a 3.70 might be a good idea. If it has a larger cam and side drafts? The Z22 got ok mileage,


Posted Image

#13 wayno

wayno

    Datsunahaulic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 12,980 posts

Posted 28 April 2017 - 07:50 PM

I get 23mpg on the hiway going 70mph with my LZ23 when I am not pulling my trailer and the flatbed is empty, but with the trailer I likely get 10/12mpg around town, unfortunately I usually have the trailer connected, and the flatbed is full most the time, it is my work truck.


 

 


#14 flatcat19

flatcat19

    Back in Black

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 19,943 posts
  • Location:Tri-Cities, WA/PDX
  • Cars:Smaller. Better. Slower. Lower.

Posted 28 April 2017 - 09:07 PM

When I got that blue 521 my sister used to own...I think my math was about 6mpg. Granted, I was blasting that thing all over. That thing was fast.

Kevin's got about 8mpg. I also think k his carbs were running a bit rich though.

You can't hang if your nuts haven't dropped...it's physics


#15 ErickwithnoK

ErickwithnoK

    Advanced Member

  • Members
  • PipPipPip
  • 192 posts
  • Location:Oregon
  • Cars:620

Posted 28 April 2017 - 09:29 PM

As long as I get 12-15mpg I'm fine with it. Not my biggest concern. It's definitely a nice thing to bring up though.

 

 

The 1981/1982 Datsun 720 came with the Z22 block, it makes for a torky LZ23 that will pull away from a Z24, at least mine does.

 

I know of a junk yard with 720 pickups I could pick through. My understanding is a l20 head bolts up without modification to the z22 block. Does this complicate the timing? Were you running side drafts with that setup?

 

 

Ask anyone with a L/LZ22 what that gas mileage is.


Last LZ23 I saw got around 8-10 mpg.
The LZ22 I had went though a tank in a couple of hours.

No need to go all out. A moderate L20B build will net you a quick whip.


Cheap, fast, reliable. Pick 2.

 

Fast, reliable. Depending on what you mean by cheap...I do have some budget to work with haha. Would a z22 bottom end with my U67 head (cam upgrade?) and 40 dcoe's be a moderate build to you?

 

 

I have a set and working on an intake. Slowly getting there. There is a good read about them... http://community.rat...s-lots-of-pics/

 

A 'larger' cam has more lift (holds the valve open farther) and duration (holds them open longer) It's all about breathing air. The more air you can get into an engine and out again the more power it makes. Keep in mind the the higher you rev the engine the more power you make too. On the flip side, too large a cam makes the engine less fun to drive at idle and low speeds. For a 'larger' cam you will have to go after market, probably have your stock cam reground. Don't go overboard. Better to have too 'small' a cam and want more, than to have too big a cam and wish you had smaller.

 

Any good block rebuild to stock specifications will handle any head mods you might do.

 

 

The Z22 engine was used in the '81-'82 720 truck and the '81-'83 S110 200sx.

 

 

As to cutting the Z24 crank down yes but with a lot of bother. There is a reason the Z24 block is taller... it's to complement the longer stroke. Stuffing a long stroke crank into a shorter block isn't the best idea.

 

Thanks for the info, I'll read through that link. By having the stock cam reground, how does that increase the lift/duration of the cam? Are the valves open when the cam lobe isnt making contact?

 

I'll stay away from z24 cranks/blocks then. Thank you.



#16 wayno

wayno

    Datsunahaulic

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 12,980 posts

Posted 28 April 2017 - 10:24 PM



As long as I get 12-15mpg I'm fine with it. Not my biggest concern. It's definitely a nice thing to bring up though.

 

 

 

I know of a junk yard with 720 pickups I could pick through. My understanding is a l20 head bolts up without modification to the z22 block. Does this complicate the timing? Were you running side drafts with that setup?

 

 

 

Fast, reliable. Depending on what you mean by cheap...I do have some budget to work with haha. Would a z22 bottom end with my U67 head (cam upgrade?) and 40 dcoe's be a moderate build to you?

 

 

 

Thanks for the info, I'll read through that link. By having the stock cam reground, how does that increase the lift/duration of the cam? Are the valves open when the cam lobe isnt making contact?

 

I'll stay away from z24 cranks/blocks then. Thank you.

The Z22 block needs some holes drilled in it, sealik and I have wrote threads that talk about this, here is a link to my thread.

http://community.rat...13-waynos-lz22/

I spent some money on my build, but if you can find a good block and have a good head you could maybe put a used engine together fairly cheap, I have done it before without issues, but the block I found had low miles on it, it's in my NL520 right now and it doesn't burn oil, but it was a fresh head on that low mileage L20b block.

The Z22 only came on the 1981/82 Datsun 720 truck, they were prone to cracking between the driver side middle head bolt and the water jacket, actually some have cracks around a lot of the head bolts, so you need to remove the head and check the block before you buy it.

You can see the cracks in the photos below along with the block designation, I used this block and it worked out for me, but it could have easily not worked out and I would have been out my money. 

DSCN0491.jpg

 

DSCN0493.jpg

 

DSCN0492.jpg


 

 


#17 Crashtd420

Crashtd420

    Senior Member

  • Senior Member
  • PipPipPipPip
  • 1,683 posts
  • Location:Massachusetts
  • Cars:1972 Datsun 521

Posted 29 April 2017 - 04:56 AM

Personal opinion if you only have a 2000 dollar budget I'd stick with your block and head as long as nothing Is wrong with them other than needing to be freshened up.. the l20b blocks are suppose to be pretty solid and that head has good size valves and intake runner to start with.... you'd be surprised how quickly you can piss through 2000...
Look at the whole picture...
Including your compression ratio,
Carb choices, piston, cam etc.... every decision effect the next part in line..
Start with the machine shop and see how far you can go with the budget you have..
Goodluck

#18 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 70,285 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 29 April 2017 - 05:42 AM

This above.

 

Later source a Z22 engine block and make an L 22.


Posted Image

#19 flatcat19

flatcat19

    Back in Black

  • Senior Member
  • PipPipPipPipPipPipPipPipPipPip
  • 19,943 posts
  • Location:Tri-Cities, WA/PDX
  • Cars:Smaller. Better. Slower. Lower.

Posted 29 April 2017 - 06:39 AM

L20B bored to 86mm for 280zx NA flattops. Spend the rest of that money for a 38/38 Weber and headwork on that U67.

If dead set on an LZ, build it as a side project. The cost versus output doesn't add up. Easier/cheaper to spend that same money on a KA.

You can't hang if your nuts haven't dropped...it's physics


#20 ErickwithnoK

ErickwithnoK

    Advanced Member

  • Members
  • PipPipPip
  • 192 posts
  • Location:Oregon
  • Cars:620

Posted 29 April 2017 - 08:08 AM

The Z22 block needs some holes drilled in it, sealik and I have wrote threads that talk about this, here is a link to my thread.

http://community.rat...13-waynos-lz22/

I spent some money on my build, but if you can find a good block and have a good head you could maybe put a used engine together fairly cheap, I have done it before without issues, but the block I found had low miles on it, it's in my NL520 right now and it doesn't burn oil, but it was a fresh head on that low mileage L20b block.

The Z22 only came on the 1981/82 Datsun 720 truck, they were prone to cracking between the driver side middle head bolt and the water jacket, actually some have cracks around a lot of the head bolts, so you need to remove the head and check the block before you buy it.

You can see the cracks in the photos below along with the block designation, I used this block and it worked out for me, but it could have easily not worked out and I would have been out my money. 

DSCN0491.jpg

 

DSCN0493.jpg

 

DSCN0492.jpg

 

Pulling the head may be difficult to do in a junk yard, and getting someone to sell me just the block would be tough as well. I will do my best to investigate any z22 block I come upon, thanks for the photos those are super informative. I'll be sure to read through your thread.

 

Personal opinion if you only have a 2000 dollar budget I'd stick with your block and head as long as nothing Is wrong with them other than needing to be freshened up.. the l20b blocks are suppose to be pretty solid and that head has good size valves and intake runner to start with.... you'd be surprised how quickly you can piss through 2000...
Look at the whole picture...
Including your compression ratio,
Carb choices, piston, cam etc.... every decision effect the next part in line..
Start with the machine shop and see how far you can go with the budget you have..
Goodluck

 

Honestly when I think about spending more than 2k on my 620 it makes me feel like...it's just a 620. It has a lot of value to me, but I respect all of your opinions and would like to own a Z or a 510 some day and if I have a lot into my pickup it will be tough to get into anything else. So I'll just rebuild what I have. I didn't realize my U67 head already had larger valves than other L series, that's really interesting and seems like a good thing for my application. If I go with a rebuild on my l20 (possibly a mild bore for larger pistons like flatcat suggested, I'm sure the 38/38 would work great but I want side drafts, just for fun), what kind of costs should I be expecting? I would also be finding some dcoe's, after reading through the R1 thread I think it's a bit out of my league. Would I want to port my head?