L20A tear down

[rayaapp2]

Hey guys

 

I have a L20A from an old Fairlady. I believe its a 75+ as per the FI injector ports in the E30 head.

I was having fun noting the differences between this motor and what we received in the states.

L20A

Pretty nasty when I first pulled the head. It turned over so I kept it.

I gave it some penetrating oil so I could get it apart easier.

The E30 head.

I noted 4 key differences in the head as compared to a E31. The combustion chamber is ever so slightly different in shape. There is a KEY ridge between the 2 valve seats. Both the intake and exhaust valve seem to be smaller than the E31 and much smaller than the late style E88 head(I had a set of late E88 valve nearby). And finally the most distinctive feature is the smaller intake runners.

 

Moving to the bottom end again. The Domed pistons stick out. They remind me of some of the Roadster pistons Ive seen in the past.

Then noticed that when I was putting the pistons down the cylinders to leave them for the night I saw that the big rod end will not fit down the bores with the rod caps in place.

 

I also noted the "M3" casting. Ive seen the M1 and M2 casting on the smaller L16 engines and such.

 

It appears other than dealing with the piston set that I will also be in for a crank polish. All the bearings on the crank are past the babbitt and down almost to copper. That is to say little bits of copper are showing threw the bearing surface. It must have been low on oil or run on really dirty oil.

 

Anyway guys, I thought I would share as most of the time you just dont see one of these things. With the domed pistons and combustion chamber design I think I can understand why the Japanese never went to the larger displacements. There wasnt much of a need.

[Xnke]

Those piston crowns look BEEFY.

 

How much does a piston/rod assembly weight?

 

As for pistons; there are some solutions to that. Lookin at the block, I can't help but wonder about cylinder wall thickness.

[NZeder]

Check the Compression height of the pistons. If it is a pre 79 L20a it should have 40.1mm CH and if post 79 it will have 38.1mm as the rod length was changed from the 133mm on the pre 79 (ie same rod as the L24) to a longer 135mm. However the Longer 135mm items run a smaller big and little end so that will be a give away also. The big end journal should be 53mm and little 21mm for the pre 79 engine. The post will have 51mm and 19mm.

[rayaapp2]

Thanks for the heads up. Ill definitely be checking to see what bearings to order. I almost ordered them.

[blue72]

Thanks for all the pics. It's kinda difficult to come by nice high resolution pictures of these engines. Most Japanese sites seem to have really small pictures for some reason.

[ozconnection]

Are you going to put that motor back together?

 

That E30 head is the perfect 'clean slate' for a radical head build up, especially the inlet ports being as small as they are. Just a thought.

[kolonelklink87]

intake ports on the e30:

It seems from the images that nissan left the shortside radius alone and moved the longside down to make the narrower port... my un-trained instinct would be to do the oppposite; any ideas on why they took this approach?

[Tony D]

could be they left the cores for the water passages alone, or made them larger in the L20A (this one is actually an L20E...)

[rayaapp2]

Alright Tony, what is the L20E? Perhaps the post 79 L20 6? And how can you tell without measuring stuff?

 

My plan is to just rebuild it and have it as a backup in case the engine under the hood currently is toast. We know that the engine in the car turns about 2" on a 1/2" drive ratchet on the crank pulley, but the cam is really rusty even though the valve cover has been on and sealed. Car has been sitting since about 1987 and hasnt been touched. Not going to be doing any radical stuff to the motor. I just want to get the car running. In the future Id like to do a VH45 or Y44 swap into the car. The L20 is a cool motor and should get the car around until I finish up some of my current projects.

 

 

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I cant find much info on the L20E after searching a little.

This is a rear sump/mid sump motor. So the only options I know of that this motor was available in was the Laural or the Fairlady Z. However Im not uber well versed in Nissan models. When I think "E" I think L24e with small rod bolts. I checked and the bolts are the same as L28et which is the only other L series rod I have left around here not in a motor. I believe that is the larger bolt anyway.

Edited February 24, 2010 by rayaapp2

[NZeder]

Alright Tony, what is the L20E? Perhaps the post 79 L20 6? And how can you tell without measuring stuff?

 

My plan is to just rebuild it and have it as a backup in case the engine under the hood currently is toast. We know that the engine in the car turns about 2" on a 1/2" drive ratchet on the crank pulley, but the cam is really rusty even though the valve cover has been on and sealed. Car has been sitting since about 1987 and hasnt been touched. Not going to be doing any radical stuff to the motor. I just want to get the car running. In the future Id like to do a VH45 or Y44 swap into the car. The L20 is a cool motor and should get the car around until I finish up some of my current projects.

 

 

-------------------------

 

 

I cant find much info on the L20E after searching a little.

This is a rear sump/mid sump motor. So the only options I know of that this motor was available in was the Laural or the Fairlady Z. However Im not uber well versed in Nissan models. When I think "E" I think L24e with small rod bolts. I checked and the bolts are the same as L28et which is the only other L series rod I have left around here not in a motor. I believe that is the larger bolt anyway.

Ok the L20a is commonly used to describe the twin SU or single downdraught carb'd 2L L6. The L20E as you might guess is the same engine ie 2L L6 but with EFI. Much like there is L28 and L28E (L28 is usually found here in NZ in Nissan Patrol).

 

As I posted earlier there is 2 types of L20E that I know of the pre 79 and post 79 which have the differences stated above. I guess there might be other differences like those for the early N42 and later N42 L28 blocks but I don't know what they are if any

 

Cheers

Mike

[kiwi303]

This is an L20 A I am watching, if it's still around come May, I moght pick it up when I'm in the North Island at a conference. Notice the single downdraft, like an Arizona 4bbl manifold but with a smaller carb.

 

http://www.trademe.co.nz/Browse/Listing.aspx?id=273822334

 

I could have a full van on the trip home, I'll be picking up a Cleveland 302ci short block on the way back, and an L20B short block, with possibly this L20A and 4spd if it's still hanging around on Trademe at the time.

[Daeron]

And, in case the original poster was unaware, an L20B is a four cylinder, 2 liter L-series motor.

[2fast2Z]

Deleted, due to double posting

Edited February 26, 2010 by 2fast2Z

[2fast2Z]

Are you going to put that motor back together?

 

That E30 head is the perfect 'clean slate' for a radical head build up, especially the inlet ports being as small as they are. Just a thought.

Just curious, how would you attack that head ?

 

Chris

Btw. can't see the pics Ray

[rayaapp2]

Hey Chris,

 

Im just going to do a valve job on it, hot jet wash it, and clean the HG surface with the mill for a good seal.

Im not planning on a whole lot more than that. I might use some of that can of pink crack detector stuff on it to make sure it has good combustion chambers before I go through all that.

 

My Bandwidth is being limited by my ISP right now. It has been for just over a week. They had a plane crash into one of their main hubs that services my area. Its caused many problems with our cable, phone, and internet. We've been issued a refund for the inconvenience, but Im still noticing slow connectivity even on my end. I also have been busy posting pictures lately and sharing lots of my bandwidth with the video games. So Ive been pushing it. My server actually shut itself down last night. I havent figured out what happened yet. I may have just had a large influx of usage at sometime last night. Its a Windows Corp. XP system. I almost installed Server 2003 on it not long ago, but there isnt enough if any gain on my network to waste the time. Im really getting frustrated with Windows though. Im still living with Corp XP on most of my computers, because I do not like any of the new operating systems since XP corp. edition. The goal is to keep everything free at this point so I have no plans to upgrade beyond what we normally pay for our regular services. It is what it is I guess. Pictures should be back up. Someone from Ratsun has offered to host some of my pictures so I sent him a folder. Hopefully this will ease up some of my usage.

 

How are the Roadsters and Z?

[Tony D]

Just curious, how would you attack that head ?

Chris

 

Same as ANY L-Head. The 'clean slate' refers to the ability to simply REMOVE metal to give you a profile that you want as opposed to having to weld in metal to close combustion ports, etc...

 

The biggest problem with an L is getting a quench head configuration, and most heads fully built will have the CC welded and the head redecked. With the L20A head, you don't need to weld the head, and you don't need to deck it and loose lifetime on it, you simply start reshaping the chamber-since it's so small, you are virtually unlimited in what configuration you can use.

 

Everybody changes the valves anyway, so that's not even worth mentioning...

[kolonelklink87]

I know the e30 is *meant* to be a closed head... but from that photo it looks to be open chamber? can you clean it up a but to get a better view?

[2fast2Z]

Ray, the photo shows up now, maybe your server went down at the moment i was looking at the topic.

 

Roadster and Z are fine, they are in the garage at my summer house, last year i extended that garage and now there is room for both, currently doing a little work on the Z when i'm there, putting on triples (My balance tube topic) and improve ignition, getting it ready for spring time, i also want to do some suspension work, i will e-mail you about that.

 

TonyD, ive started a new topic, so i dont jack Ray's topic E30 head any comments will be appreciated.

 

Chris

[Daeron]

I know the e30 is *meant* to be a closed head... but from that photo it looks to be open chamber? can you clean it up a but to get a better view?

Pete: The circle you are seeing is just a difference in shading of carbon; if you go check out the Head Differences sticky thread, someone pointed out the same thing about an E31 or some other closed-chamber head there.. (it may have even been me, I can't recall) but it was just a photographic illusion.

[kolonelklink87]

Pete: The circle you are seeing is just a difference in shading of carbon; if you go check out the Head Differences sticky thread, someone pointed out the same thing about an E31 or some other closed-chamber head there.. (it may have even been me, I can't recall) but it was just a photographic illusion.

 

D: I hear what you're saying... its a pretty convincing illusion on the intake/exhaust side of the CC... i'm really not sold on this one way or the other... i'd like to see a clean pic