Datsun l20b rebuild advice

[DATSUN671]

im currently rebuilding my l20b.

 

my main concern is the bottom end.

 

on the bottom end the piston has scratches on the side is this normal?

 

what do you suggest i do?

 

thanks for the help

[bonvo]

pics

[Zeusimo]

We Suggest You Post Pictures

[RTB]

Pictures required. If it is deep and there are scratches on the block as well then 100% yes you need new pistons and probably a hone.

[DATSUN671]

Here's a pic of the piston and the cylinder bore

 

http://s1119.photobucket.com/user/Niyota/media/Mobile%20Uploads/image_zps2f9b8b92.jpg.html

[DATSUN671]

Pic of the cylinder bore

http://s1119.photobucket.com/user/Niyota/media/Mobile%20Uploads/image_zps0fc5ff96.jpg.html

 

Thanks for the help

[ggzilla]

Piston looks fine to me, very light scratches are normal

 

 

Can you take photos not so close, should turn out clearer.

[kgrantkey]

I thought I was gonna see some real scratches. Like when I was a kid and didn't put the keeper in properly on a full floating rod in my dirtbike. It really made a bad deep scratch. I just honed it a touch and replaced the rings making sure to put the rod pin keepers in correctly on the piston this time, It was a two cycle so it was gonna smoke anyway, 

 

I could hardly tell the cylinder was scratched. Ran great. Good little Yamaha.

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From what my untrained eye sees......

Looks like the wear is on the side that gets pushed hardest against the side of the cylinder causing it to wear more on the sides and can make the cylinder become out of round so to speak and increase the wear on the side of the piston. I know guys that would hone and re-ring until the piston slap was too loud to ignore. 

 

 

A good machine shop can knerl  the pistons and hone the cylinders but a bore job and new pistons would make it like new. Sometimes it's a question of what the car is worth to you versus what it takes to make it into a dependable engine.

 

 Over the years I've seen some guys do some cheap tricks to keep their truck running, and it's not what I do for a living so some on here could probably tell some stories.

 

 

my main concern is the bottom end.

 

 

I think most consider the "bottom end" to be the crank and bearings.

[datzenmike]

There will be a wear ridge at the uppermost travel of the top ring. Generally if you scratch your finger nail up the cylinder and it catches, it needs to be re bored. Yes I know everyone has had worse and simply ringed and honed it and it ran fine but I bet you didn't drive another 150K on it. Lucky to get 50K. The rings are not going to seal properly at the top where there maximum wear and pressure.If it's worn get it bored. My Z22 block was punched out 1mm for twenty bucks a cylinder. New Silvolite pistons and you have a brand new motor capable of a couple of hundred thousand miles because YOU will be looking after it, not the 3rd or 4th owner driving the shit out of it. I don't include rings because oversize are the same cost and you have to buy them anyway. When you re bore you can then run chrome rings because the bores are perfect. Irregular tapered or oval bores need cast iron rings to quickly wear in.

[DATSUN671]

I was reading on the mods u can do to the l20b and I'm planning to do the big bore set up with the ka pistons. My question is , Is the l20b and the z22 crank different? It says to use the z22 but I was wondering if I can use the l20b with the ka pistons?

 

Thanks for the help