All this Gas helps Ruredi on information ;) he needs it.
Stu I think if your Z18et block is as tall as the L20b then
you probably have Z20E conrods which are 152.5mm otherwise
with 145.9mm l20b rods you have way too much room left with
the L18 crankshaft unless previous owner used tall piston.

Rb30 forgies leave 2 spare for overboost or damage :)
SR forgies have the wrong pin diameter for L rods ;)

http://www.youtube.com/watch?v=AwV7ZTyHY4M

There L18 rods and L20 pistons mate I know the guy that built the motor

Keep the comments and advice coming. All beneficial in the end.

No worries il keep posting then . Also being a 72 you mite get away with an aftermarket ecu depending on what engineer you use

Will depend what year block he uses stu. Pre 73 block easy due to for emissions, after that ir gets harder

Umm interesting but do they have numbers for engine blocks that have not been registered for more than 20 years? I heard they fall of the computer listing after that time and there are a few guys on ozdat that have the original L16 just collecting dust for 3 decades or more since most where upgraded to L18/20.

Stu L20B 38mm sky scraper high pistons make sense now :)
bloody tall but tough as nails esp. new high silicon castings.

Ruredi will only have space for 32mm and under but the 1.547 rod stroke ratio is going to be an even better fast combustion process that reduces detonation and then can afford a bit more compression to start with.
Im not sold on low comp motors as they are just tired motors without the boost. The Zet was not the pollution engine most peeps think it was, the EGR is not as big as in the NA version of the same Z motors.

Some good history is that the DR30 FJ20ET bathurst racers that replaced the Z18et Bluey where a tad lighter but never came close to smashing the fastest lap for Hardies Heroes :)
So the midrange torque helped by semi hemi pro swirl chambers with twin spark and high boost had better results than the 4 valves with modern styled tumble pent-roof chambers.

a few things for ruredi. im not sure what people are worried about re: stressing about year of block for emmissions etc. I have a 93 model sr in my 1600 and the engineer was going to pass with aftermarket ecu.

call an engineer (sanjay) and get him to give you an idea of what you need to do. tell him only what he needs to know, not about all the plans with different internal bits, just capacity or engine. thats the best plan so you know you will be right

about all this spruking on the Z head... its common knowledge that it is a bit of a dud. its great for crossflow design but thats about it. its designed around good emmissions rather than performance. the ports are more restrictive than L series, can't be ported much because of water jackets and the combustion area issues equal a poor burn.

im not trying to bag the z head just for fun just counteract D's tent pitching rant about them every other post. dont get me wrong D is a wealth of info, i just think that if you take what you like out of info on the internet you;re not getting the full story. as long as you do your research and are happy.

you are welcome to come for a spin in my car and see what 220kw in a datsun feel like, although its not really similar to a revvy motor in a lighter solid axle car - itll make you smile

The Dud donk was in my family and so was the mk II FJ20et, yet the dud motor was a winner in all areas with same turbo and boost albeit some head work, L20b internals etc.
When my father had enough of losing to brother Luis he went for KKK (to4 hybrid equiv) hybrid snail custom mani, mildly ported head with more boost (30-35psi) prepped stock Mk2 rods with forged slugs, made almost 280kw atw & still wasnt that much faster. C16 leaded fuel 550cc inj made over 300kws w/ stock cams.
My R100 BP made 200+kw ate and was 200kg lighter than most datsun 1600s & no offence but would never own an SR powered oldskool 60/70s car just doesnt look right or do way more than some older nissan engines.

I'm enjoying the difference of opinions here and I encourage them to keep coming.

My opinion:

Now I don't know as much as you guys all do as I'm still learning however in relation the Z18ET head that a lot of people are dismissing...

1. It has been used in race applications with some very successful results. And still is being used by some (Troy Morrow) with impressive results. I'm sure they are not standard heads and have had plenty of work done to them.
2. Stu is using it on his 120y and from what I hear and see...it's a pretty cool little weapon...if i could get my car going with those numbers i thibk id be happy. He's running it on gas also...so I can only guess that on petrol it might even go better (not to bag your setup at all Stu)
3. Ease of using the standard efi setup than converting an L series???
4. Many of people have used this head with good numbers and have had good results.

So to say that it is a "dud" is probably a bit far. There is still plenty of good about the head.

No offence taken mate And yes you will gain more power on fuel like Leigh said speak to an engineer first and see what your option's are. Depending on what sort of power your after I see no reason why a L/Z combo on fuel with decent manifolds and a roller turbo wouldnt crank out at least 150rwkw on relatively low boost.