Where to find 10:1 compression pistons L20B

[Guest nateoneel]

Where can I find 10:1 compression pistons for my L20B engine? I'm having a little trouble finding them through local parts shops. I don't want do any block swaps or crank swaps. Just bore and higher compression.

Any ideas guys??

[phatdave]

http://cgi.ebay.com/ebaymotors/Datsun-Z-240Z-280Z-510-620-New-86-5mm-Flat-Top-Pistons_W0QQcmdZViewItemQQcategoryZ6763QQihZ027QQitemZ400011829962QQrdZ1QQsspagenameZWDVW

[datzenmike]

Get a set of Z20E piston/rods from an '80-'81 200sx. Stock bore 85mm with open chamber head gives 9.941 compression. Closed chamber head.... 10.687. The pistons are flat tops with very small valve reliefs in them. Actually all you need are the 152.5mm long rods and mount .5mm (or what ever) over size on them. The piston pin height has to be 31.75mm to work with these rods. All Nissan parts.

[Guest nateoneel]

dude you are the god of datsun knowledge!!!

[Guest nateoneel]

Sorry if I don't know this one but what does open or closed camber heads mean?

[famousyellowz]

Will 280zx pistons work?

 

I think that's what I had in my L20B back in the day. They were flat tops, I think 10 over bore.

Edited November 25, 2008 by famousyellowz

[datzenmike]

'81-'83 280zx flat tops will work but you have to over bore the L20B 1mm to fit them.

[datsunfish]

Wouldnt L18 pistons slide right in? Then maybe a peanut head would put it somewhere close..?

[datzenmike]

Sorry if I don't know this one but what does open or closed camber heads mean?

 

An open chamber head is a head with a combustion chamber that extends over the whole cylinder width and would be circular in shape.

 

This is a good example of an open chamber head from a Z24 engine.

http://i138.photobucket.com/albums/q251/datzenmike/00770016.jpg[/img]"]

 

A closed chamber can be any shape and does not extend to the cylinder walls. In addition, the piston comes up to and is as close as the head gasket thickness away from the head surface. As the piston approaches TDC the piston violently pinches the air trapped in this zone forcing it into the open area. This causes beneficial swirling and additional mixing and blending of the fuel air and a more efficient burn. The swirl effect also helps to homogenize the cylinder temperatures thus reducing hot spots that can lead to pre-ignition. The pinch area is also known as the quench or squish area.

 

 

Here is a closed chamber head.

http://i138.photobucket.com/albums/q251/datzenmike/headL245hp1.jpg[/img]"]

Edited November 25, 2008 by datzenmike

[datzenmike]

Wouldnt L18 pistons slide right in? Then maybe a peanut head would put it somewhere close..?

 

L18 would work same as the Z20 but you would be able to use the L20B rods. I think the L18 flat tops are almost impossible to find now aren't they?

[Guest nateoneel]

An open chamber head is a head with a combustion chamber that extends over the whole cylinder width and would be circular in shape.

 

This is a good example of an open chamber head from a Z24 engine.

http://i138.photobucket.com/albums/q251/datzenmike/00770016.jpg[/img]"]

 

A closed chamber can be any shape and does not extend to the cylinder walls. I addition the piston comes up to and is as close as the head gasket thickness away from the head surface. As the piston approaches TDC the piston violently pinches the air trapped in this zone forcing it into the open area. This causes beneficial swirling and additional mixing and blending of the fuel air and a more efficient burn. The swirl effect also helps to homogenize the cylinder temperatures thus reducing hot spots that can lead to pre-ignition. The pinch area is also known as the quench or squish area.

 

 

Here is a closed chamber head.

http://i138.photobucket.com/albums/q251/datzenmike/headL245hp1.jpg[/img]"]

 

Thanks for breaking that down for me in english. I learned something new! :)

[banzai510(hainz)]

mike I though Napz pistons have a lower pin height?

 

I thought there is alot of headgasket proplem when installing flattops.?

 

natoneel ,

whats the big Boner oover 10-1 compression?

Gas isnt that good anymore. Might be asking for proplems,detonation timming issues

 

280zx NON turbo 81-83 piston (86mm) is the flattop which will be a +1mm over in a L18/20(85mm)

[datzenmike]

True, all of the L have the highest pin heights and the Z are overall much lower. This allows L20B rods to be used in the Z22 and longer rod lengths in all the others. Longer rods counteract the increase in stroke length as the engine size grows. Indeed a Z24 has a higher rod/stroke ratio than an L20B.

 

Only problem with head gaskets I can think of when flat tops are used is increased stresses incurred with increased compression. Stock gaskets, arguably the best you can buy, are for 8.5 compression. It's a testament to their design and quality that they will work far above that. But they can and will fail if pushed and are blamed for it when the cause is more likely just compression increase.

Edited November 25, 2008 by datzenmike

[datzenmike]

dude you are the god of datsun knowledge!!!

 

Let me think about that.................... No. That would be Hainz and or datsunaholic.

[banzai510(hainz)]

the head gasket issue what I can tell is

Most stock nissan/Felpro/Victor renz gaskets are very close to the bore @85mm.

Boring it over 1mm is getting close to getting the gasket to the bore.

Maybe a bigger gasket is needed.

[datzenmike]

The 'fire ring' should be back from the bore edge a bit to keep it cooler. Bigger is better I think too. Z4s are notorious for blowing (even stock gaskets) at 100K. The manual says to loosen each head bolt one at a time (no special order) and re tighten, at every tune up. Only happens if at the dealer, bet no one ever does that! But it's Nissan's way of managing the problem.

[hang_510]

i have a set of Arias forged DOMED high copmpression pistons, rings, pins @ 88.5mm

easily machined to get the 'perfect' CR

 

 

nismo HG required = 88.5mm

[datzenmike]

3.5 over bore on an L20B would make a 2.11 liter motor with 10.55 compression if flat top pistons are used... higher if domed.

[hang_510]

supposedly around 11.5:1

[Guest nateoneel]

i have a set of Arias forged DOMED high copmpression pistons, rings, pins @ 88.5mm

easily machined to get the 'perfect' CR

 

 

nismo HG required = 88.5mm

 

Are those pistons installed and working or for sale? :D If installed please tell me a little reveiw of what you think about them.

nate

[datzenmike]

More important what rod length is used?

[RacnJsn95]

Can't you just run L18 pistons, and a closed chamber head, and get real close to 10:1? Ozdat thing says 9.835:1? Maybe shave the head .015" and run some head shaver shims, could probably be a little over 10:1.

[datzenmike]

L28 flat top pistons in an L20B with closed chamber head would be .... 10.68.

 

L18 pistons with 4.36cc dish and closed head would be..... 9.915

Edited November 26, 2008 by datzenmike

[sdsurf]

so if I put 280z pistons (flat top) with stock L20b rods in my L20B My compression would bump to what? And I would have to overbore by 1mm, correct?

[datzenmike]

'81-'83 280zx flat tops will work but you have to over bore the L20B 1mm to fit them.

 

This would produce a motor of 1,997cc and if used with an open chamber head would have a compression of 10.12 With a closed chamber head it would be 10.87