'80 720 L20B

[KDW_80-720]

I can’t find a Z22 anywhere even for parts. I was looking for one and don’t have anywhere to put a parts truck lol 

 

I Might keep this one a little closer to stock and just clean it up and maybe go a little bigger on pistons. 
 

I really want to build a go fast 620, so if I spend a ton of money on motor I’d rather do it for that one 

[datzenmike]

If going to overbore go to the max 1mm and get the 1mm oversize pistons and rings. Might as well it cost the same.

 

Z22s were also used in the '82-'83 S110 200sx. But have a care as the later ones had different rods/pistons... so use your L20B rods instead as they are the same as the truck Z22. 

[EDM620]

23 hours ago, datzenmike said:

Even worse today. Mechanics don't like to work, they don't and can't fix things, only replace old, worn broken parts with new ones.

This unfortunately too true these days, training and service manuals says what module to replace and not how to fix. This is the joy & curse of being a backyard mechanic, and keeps us folks less reliant on the dealerships for service (BTW, the service dept. is where dealers make most of their money, not on car sales).

 

8 hours ago, datzenmike said:

The ports and the exhaust manifold now match perfectly (and are larger) and without a lip. While you are there you can do the intake and intake ports as well.

Fairly easy to do, just be patient and don't get too aggressive on grinding into the aluminum. I think I posted the before & after grind on my post, but here it is again for reference. I covered the area with sharpie then as described used the gasket to trace. Do your manifolds the same way.

 

[KDW_80-720]

1 hour ago, datzenmike said:

If going to overbore go to the max 1mm and get the 1mm oversize pistons and rings. Might as well it cost the same.

 

Z22s were also used in the '82-'83 S110 200sx. But have a care as the later ones had different rods/pistons... so use your L20B rods instead as they are the same as the truck Z22. 

 

so if we were to bore out 1mm and use flat top pistons what would the compression be on that? Assuming it’s bored out 1, I have to get it bored due to the wear anyway. 

[wayno]

I have a closed chamber head on a Z20s engine with flat top pistons, Mike told me it had a 10.8 to 1 compression ratio.

[KDW_80-720]

6 minutes ago, wayno said:

I have a closed chamber head on a Z20s engine with flat top pistons, Mike told me it had a 10.8 to 1 compression ratio.

My buddy and I are thinking boring to 86ish and putting some flat tops with some connecting rods and such. With my peanut head

[wayno]

Personally I would not build anything that you cannot use/burn premium pump gas in if I were you, I am lucky to be near 2 stations with premium(92) ethanol free fuel, I use it in everything but my work truck and diesel builds, I even use it in my lawn mowers, blowers, rototillers, edgers, pressure washer(small one), and my chainsaws as it doesn't spoil like pump gas, my business pressure washers(big ones) use pump gas, they were made for that gas, I rotate my two commercial pressure washers every month or so so the gas in the plastic tanks don't spoil and cause me issues.

Like i mentioned I re-curved my distributor in that truck, I think the knocking/pinging was why I lost a head gasket, it was timed at 0 degrees and it still knocked at the end just before I lost the head gasket, I re-curved it too late, but now it is fine at 6 or 7 degrees BTDC with the modified distributor.

 

[datzenmike]

7 hours ago, wayno said:

t, a Z22 block bored out to except stock 89mm Z24 dished pistons, I put a closed chamber head on mine and Mike said it was 8.9 to 1 compression ratio.

 

8.825

 

 

2 hours ago, wayno said:

I have a closed chamber head on a Z20s engine with flat top pistons, Mike told me it had a 10.8 to 1 compression ratio.

 10.7

 

Close enough.

 

 

2 hours ago, KDW_80-720 said:

My buddy and I are thinking boring to 86ish and putting some flat tops with some connecting rods and such. With my peanut head

 

Later (even used) 280zx pistons are 1mm larger than your L20B and are flattop. I guess you could by new 1mm over size zx pistons and bore to 87mm. All L series pistons have the same pin height so they will fit your L20B rods and not hit the under side of the head. 10.87 compression because 86mm bore not 85mm. I'm not a fan of big compression numbers. Each compression point increase might (on a good day) get you a 4-6% power increase. This would be a hair over two points so (on a good day) lets just round to 8%. On a 93 HP L20B that's 100 HP but only at 5,500-6K. Around town speeds it's one or two HP.

 

It's a free increase in engine efficiency and if combined with cam, carburetors, larger valves, head work, better exhaust it's 8% of what ever that makes. The down side is making it work without blowing it up. Higher compression burns faster so retard timing and you'll want to run high octane gas and colder plugs.

[KDW_80-720]

1 hour ago, datzenmike said:

8.825

 

 

 10.7

 

Close enough.

 

 

 

Later (even used) 280zx pistons are 1mm larger than your L20B and are flattop. I guess you could by new 1mm over size zx pistons and bore to 87mm. All L series pistons have the same pin height so they will fit your L20B rods and not hit the under side of the head. 10.87 compression because 86mm bore not 85mm. I'm not a fan of big compression numbers. Each compression point increase might (on a good day) get you a 4-6% power increase. This would be a hair over two points so (on a good day) lets just round to 8%. On a 93 HP L20B that's 100 HP but only at 5,500-6K. Around town speeds it's one or two HP.

 

It's a free increase in engine efficiency and if combined with cam, carburetors, larger valves, head work, better exhaust it's 8% of what ever that makes. The down side is making it work without blowing it up. Higher compression burns faster so retard timing and you'll want to run high octane gas and colder plugs.

Hmm...I’ll probably dyno tune it at that point. Adjust head gasket thickness as needed

[KDW_80-720]

43 minutes ago, KDW_80-720 said:

Hmm...I’ll probably dyno tune it at that 

[datzenmike]

Or run an open chamber head and lower the compression.

[EDM620]

If putting a turbo on at some point is in your mind, you might not want to build to a higher compression...

[KDW_80-720]

1 hour ago, EDM620 said:

If putting a turbo on at some point is in your mind, you might not want to build to a higher compression...

I don’t plan on one for this build. One day I’ll do a turbo 620 maybe, but this one I just want a little bit more since I’m already having to get The block overbored due to wear 

[KDW_80-720]

On 6/30/2020 at 8:18 PM, datzenmike said:

Water passages look plugged.

They are, at it looks like it’s by design, someone plugged them with something. I tried to chip away at it and nothing coming out of it. 

[datzenmike]

 

 

Open chamber W58 front to the left.

 

Looks like maybe the ones that look plugged are just s gasket imprint

[KDW_80-720]

I’ll work on cleaning those up, although I’m not sure the point if I’m taking it to the machine shop anyway. 

[KDW_80-720]

On 7/2/2020 at 7:32 PM, datzenmike said:

 

 

On 7/2/2020 at 7:32 PM, datzenmike said:

I guess you could by new 1mm over size zx pistons and bore to 87mm. All L series pistons have the same pin height so they will fit your L20B rods and not hit the under side of the head. 10.87 compression because 86mm bore not 85mm

 

Sorry, this has 87mm and 86.  Is this 10.87 compression at 86 or 87?

 

If I were to get some slightly smaller dish that isn't the 11cc, maybe 4? What would that drop my compression to?

[datzenmike]

L20B is 85mm bore.

 

Bore to 86mm you can use stock 86mm L28 flattop pistons. Compression 10.87 with closed chamber head

 

Bore to 87mm you could use 1mm oversize 87mm flattop L28 pistons. Compression is 11.0 with closed chamber head

 

 

There are a couple of other 86 or 87mm pistons but are not L series and then you would need to hunt up rods to make them work. Best easy way to drop the compression is an open chamber head. BTW.... closed chamber heads only work properly with flattop pistons. Dished pistons defeat the purpose of a closed chamber head.

[KDW_80-720]

28 minutes ago, datzenmike said:

L20B is 85mm bore.

 

Bore to 86mm you can use stock 86mm L28 flattop pistons. Compression 10.87 with closed chamber head

 

Bore to 87mm you could use 1mm oversize 87mm flattop L28 pistons. Compression is 11.0 with closed chamber head

 

 

There are a couple of other 86 or 87mm pistons but are not L series and then you would need to hunt up rods to make them work. Best easy way to drop the compression is an open chamber head. BTW.... closed chamber heads only work properly with flattop pistons. Dished pistons defeat the purpose of a closed chamber head.

Okay.

 

My pistons were dished on stock with the closed chamber head. I mean the block has to be honed and bored a little, so if I went .5mm to like 85.5.  So if we went a little over and then replaced with the flat tops, short of getting a new head, what would that put the ocompression at?

 

I'm sure there's a calculator somewhere, but I'm not sure where to find one 

[datzenmike]

The L28 flattops are stock at 86mm so won't fit 85.5mm.

 

L18 pistons have a 4cc dish and you could maybe get in 85.5 and 86mm.

 

86mm (1mm over size) L18 pistons and closed chamber head is 10.0

 

 

From Nissan (if they have them) 86mm L18 piston with pin......  12010-A8706

Rings 1mm over.............................................................................. 12033-A8702

 

You can use these numbers to cross reference a different maker.

[KDW_80-720]

Thank you!  I can work with that.  I'll try and track some down.  Not sure where to start looking for them, but thank you.

[datzenmike]

Mahle, JE, Wiseco, Arias, Carrillo..... 

[KDW_80-720]

Okay.  Thanks.

 

Those numbers are for the 4cc dished?

[datzenmike]

They are for 1mm over size L18 pistons. Replacement pistons would always have the same dish to keep the compression ratio similar.

[john510]

Good luck finding L-18 4cc dish pistons in an oversize.