so trying to figure out what do do to my L20b

[datzenmike]

Early Z22 pistons 35.5mm pin height
Used on ALL 720 truck Z22 engines... '81 through 12/'82 build dates.
and S110 (200sx) Z22E engines... 07/'81 through 12/'81 build dates

ALL Z22E pistons 32.1mm pin height

Used on S110 (200sx) Z22E engines from 01/'82 through to the end of the model year (about 07/'82)

[Lobo]

Thank you that is what I wad trying to figure out

[datzenmike]

Early.... 12010-06W11 35.5mm pin

Late..... 12010-D8101 32.1 mm pin

[Lobo]

that really helps thank you

[Lobo]

ok another question for you guys what would be a CR if i just bored the l20 say .040 and decked my head ohh i don't know 1mm i think i want to set this up to run mid to premium gas im just not sure what to do with it im going to run the u67 head for sure and i want to get a good CR what do you guys really suggest

[datzenmike]

Well, define 'a good compression ratio'. You mean the highest possible without detonation or pinging? That would depend on the fuel you plan to run, your timing, air temperature, humidity, altitude and probably several other factors. The combustion and piston design is another. Two engines can have the same compression or one higher and one does not ping.

 

To answer the question a stock L20B, 0.040" (or 1mm) over size with a U67 milled 0.040" (or 1mm) will have a compression of 9.276. Easily run on premium gas.

 

Going from 8.5 to 9.27 is less than one point of compression. Running optimal timing with a higher octane fuel, on a 90HP motor maybe 4-6% increase. Or for all the bother almost 4 hp at the top end.

[Lobo]

basically I don't want to run into a lot of issues with pinging and detonation. I like the sound of the orig setup I was thinking but this is my DD so I think I want to dial it back some more to this stock setup just bored and milled. so how far can you mill a head and if I wanted say some were around 9.5 on CR is that to high for a DD. sorry for so many questions I have never built a motor other then leaving it stock so im trying to learn about this stuff.  

[datzenmike]

To answer the question a stock L20B, 0.040" (or 1mm) over size with a U67 milled 0.040" (or 1mm) will have a compression of 9.276. Easily run on premium gas.

Above, but mill 1.3mm from head to get 9.51. That's almost 0.064" and might affect the chain slack.

[flatcat19]

Why go through all that work to mill the head for minimal gains?

 

Spend your money better. Carb(s), better clutch, better tranny.

[banzai510(hainz)]

bolt a 38/38weber DGES on there and call it good

[Nuclear Water Boy]

Above, but mill 1.3mm from head to get 9.51. That's almost 0.064" and might affect the chain slack.

 

Don't mill the head to gain compression save the head!!!! Biggest power gains are in the head as in combustion chamber, port, valve cam work. A good 9:5 compression with a well massaged head will gain excellent results without the worry of which fuel and pinging and all that. I ran a LZ22 with DAMB cam, 46mm Z SU's from ZTherapy, 10:1 compression. I also reworked the EI distributor as to NOT give to much advance right off. I recurved for a 15btdc static timing and 32degs all in by 3600 rpm<-- I think it was 32degs. Anyway ran 91 to 93 octane but typically 91 and no issues at all and it ran strong very in fact. But then sold that setup and swapped in a S14 SR20DE and the SR would own that LZ hands down easily and gets better gas milage too.

[Radim]

I'm daily driving my big bore L20B stroker, I don't see what all the fuss is about.

L20B 89MM bore
219 Head, Ti valve springs
520 Lift 287 Duration
KA24 Truck pistons
1.5MM Headgasket
Dual 40 DCOMs.

about 10:1 CR 2.3L

Get's shitty gas milage but that's about it, City/Highway driving is fun.

[datzenmike]

Cam 'n carbs are a little hairy and dialing it back would bring the mileage up but you would only drive it harder, right??? :lol:

 

 

 

Got any RPM numbers? How high do you rev it?

[Radim]

i dont rev it past 6k the cam starts making real power at 2.4k and makes it up to around 7. ill get some numbers when i get the wideband thrown in and ready. also working on EDIS4 and megasquirt with carburator TPS

[620Turbo4X4]

basically I don't want to run into a lot of issues with pinging and detonation. I like the sound of the orig setup I was thinking but this is my DD so I think I want to dial it back some more to this stock setup just bored and milled. so how far can you mill a head and if I wanted say some were around 9.5 on CR is that to high for a DD. sorry for so many questions I have never built a motor other then leaving it stock so im trying to learn about this stuff.  

 

I like your first idea too. Sounds like you have much of what you'll need to build it too.

 

I have almost the exact same setup in my 620 4X4. L20 block, crank, rods, .030 over L18 pistons, Ported W53 closed chamber W/ Isky 270 cam, 32/36. Compression on my motor is around 10.3;1 or more, due to a shaved block. No problems with detonation or pinging whatsoever… The closed chamber heads with flat top pistons respond well to the increased compression by providing turbulence at TDC. I'm running 92 octane @ 12 Deg. BTDC base timing with a lightweight spring added to one of the advance weights (to not give so much advance at low RPM's). I also limited the vacuum advance by about half, by locking down the base plate with vac advance halfway compressed against the stopper pin, since I'm not running any EGR. One thing often overlooked is spark plugs. I'm running  B8EG Plugs. As compression and engine RPM goes up, so should the number on your plugs (colder).

 

Overall, very good engine for a DD. I'm very happy with mine. Smooth idle and power delivery is pretty much like stock, just more of it. Don't have any dyno numbers but, feels as if I added another 2 cylinders to the engine. Fuel economy is actually better now than with the stock engine and easily pushes my 33" tires W/ a 4.625 rear end ratio down the freeway in 5th...

 

[Lobo]

Ok couple questions were did you get your l18 pistons and we're did you get that block off plate on intake manifold

[datzenmike]

They are likely L28 pistons.

[620Turbo4X4]

The pistons were bought from nissan many moons ago. NLA. There are aftermarket companies still selling pistons for the L18. Check silv-o-lite or ITM maybe? Perhaps someone on here may have a NOS nissan set? Post want add to classifieds.

 

 

Block off was made from 3/8" aluminum plate, cut to gasket, and 1/4" stainless "street" elbow to get the PCV pointed in the right direction (eBay). Threads were not a perfect match to the PCV, But with extra thread tape, close enough. Made my own 1 piece carb adapter from the billet aluminum too. I hate the leaky cheap two piece ones….