1980 Datsun L20B z engine into 77 Datsun 620

[datzenmike]

The Z is ok for what it was built for... good low speed torque and low emissions. With this is mind, and never intended to rev or make much power over 4K, (or highway speed) the ports are low on the head with a sharp bend at the valves to make it a semi hemi. Again it doesn't flow well above 4k because it doesn't have to. It's very efficient, very reliable,  it just doesn't lend itself to performance improvements very well. 

 

So I wouldn't say it's a bad fit for a truck. It has gobs of displacement and stump pulling torque. Perfect for pulling a heavy truck.

[SPIDERSHACKOV]

Has anyone ever thought of putting a z series head on an L20B. Flat top pistons, a cam with .575 lift and 248* duration, and some sort of a better intake system. 

[Stoffregen Motorsports]

10 hours ago, SPIDERSHACKOV said:

Has anyone ever thought of putting a z series head on an L20B. Flat top pistons, a cam with .575 lift and 248* duration, and some sort of a better intake system. 

That's the opposite of how to make horsepower.

[datzenmike]

Read my last post. Better to put a better breathing L20B head on a Z series. With flattops you get 9 to one compression. A Z series head has a 57cc combustion chamber compared to the L20B which is 45.2cc. An L20B with a Z head would be somewhere in the 7s

[wayno]

You statement above has me wondering Mike, there are different L heads and 9 to 1 with flat top pistons must be an open chamber head, as I have a closed chamber head on a Z22 block with stock Z24 pistons(dished) and was told by you that it was 8.9 to 1 CR and I have a Z20 block with flat top pistons(long rod) and a closed chamber head that you said it was 10.8 to 1 compression ratio.

I bring this up because it is very important that newbies know what they have(head) and understand what they are combining, a mistake was made several years ago and a head was rebuilt($300.00+) that was completely un-suitable for the block.

23 minutes ago, datzenmike said:

Read my last post. Better to put a better breathing L20B head on a Z series. With flattops you get 9 to one compression. A Z series head has a 57cc combustion chamber compared to the L20B which is 45.2cc. An L20B with a Z head would be somewhere in the 7s

 

[SPIDERSHACKOV]

On 5/24/2019 at 9:15 AM, Stoffregen Motorsports said:

That's the opposite of how to make horsepower.

Not looking for high end horsepower,but low end torque. These are trucks we have not sportscars.

 

On 5/24/2019 at 10:35 AM, datzenmike said:

Read my last post. Better to put a better breathing L20B head on a Z series. With flattops you get 9 to one compression. A Z series head has a 57cc combustion chamber compared to the L20B which is 45.2cc. An L20B with a Z head would be somewhere in the 7s

What makes the l20b head flow better the port size, valve size? For low end you dont want these to big, velocity from the venturi effect comes into play. 

I am asking these questions coming from the point of my experience with Harley-davidson motorcycles, sportster 883/1200 conversion to be specific. The 883 head, smaller valves and ports, has more torque and the same horsepower till about 3500-4000 rpm than the 1200 head, bigger valves and ports.

Yes the compression ratio will need to be figured out, want at least 9:1, 10:1 will be better. 

[datzenmike]

On 5/24/2019 at 10:58 AM, wayno said:

You statement above has me wondering Mike, there are different L heads and 9 to 1 with flat top pistons must be an open chamber head, as I have a closed chamber head on a Z22 block with stock Z24 pistons(dished) and was told by you that it was 8.9 to 1 CR and I have a Z20 block with flat top pistons(long rod) and a closed chamber head that you said it was 10.8 to 1 compression ratio.

I bring this up because it is very important that newbies know what they have(head) and understand what they are combining, a mistake was made several years ago and a head was rebuilt($300.00+) that was completely un-suitable for the block.

 

9 was from imperfect memory.

 

L20B/Z20 with flattops, open chamber head................................................. 9.94

Above but with closed chamber head.......................................................... 10.68

 

Z22 crank, rods and Z24 pistons with open chamber head................... 8.4

Above with closed chamber head ........................................................... 8.8

[Stoffregen Motorsports]

17 hours ago, SPIDERSHACKOV said:

Not looking for high end horsepower,but low end torque. These are trucks we have not sportscars.

 

I've been around the block a time or two, and in my experience, an L head on that motor is better, all around performer. Higher compression builds horsepower and torque.

 

If you're really concerned about torque, install a heavy flywheel too. They improve bottom end quite a bit, especially between shifts.