Aside from the engine stamp, the short blocks are about 99% the same (same rods/pistons/oil pump/water pump housing etc). Only difference is the crank pulley size is smaller diameter on the Z1.
A2 = 5.80" dia.
Z1 = 5.5" dia. (same size as JDM DC5/EP3 K20A pulley).

 

...Only difference is the crank pulley size is smaller diameter on the Z1.

Same gasket pattern or coolant/oil path pattern?

 

05-06 DC5 has the better cams!

 

Yes, they have the part #14110-PRC-030 and #14120-PRC-030. It's lobe profiles are the same as the K20A has (1411(2)0-PRC-000), they just have a bit shifted centerline on the intake cam (measured results).

 

Is this some kind of nostalgia, or something? This discussion isn't actually happening right now, is it?

K20Z1 has Type-R cams. Old news, like decades old news (ok just 15-16years).

K20Z1=K20A2 + Type-R cams + Type-R crank pulley

The cam difference is duration, between K20A2 and K20Z1/Type-R. Who cares about the centerline. The valves stay open longer because the duration is longer.

 

I have to correct something, to clear that misunderstanding.

Is this some kind of nostalgia, or something? This discussion isn't actually happening right now, is it?

There is one who was asking for the differences. Not sure if he asked for a nostalgia discussion 🤔?! He definitely was not asking for the cam differences, this was something you brought into the discussion.

05-06 DC5 has the better cams!

I commented on that, because I wanted to point out the DC5 came with different engines on the market: K20A3, K20A2, K20A and the K20Z1. USDM relevant are only A3 (02-06), A2 (02-04) and Z1 (05-06). I assume you were pointing on the Z1 engine, but for someone who is asking what are the differences of the A2 and the Z1 it might be not clear. Therefore I made clear which cams we are talking about. And if you read my post again you will know I was comparing the ITR (K20A engine, cam part #1411(2)0-PRC-000) and 05-06 DC5 Type S (K20Z1 engine, cam part #1411(2)0-PRC-030). Those cams are compared by valve lift measurement the same beside the intake centerline difference.

The cam difference is duration, between K20A2 and K20Z1/Type-R. Who cares about the centerline...

That's indeed correct, something 6spd_EK measured by valvelift variation in 2013 I believe, but that wasn't my point. If you look into the part numbers you will know I was talking about the K20A cams vs. K20Z1 cams.

 

The K20A2 and K20Z1 heads have the exact same casting (PRB), the only difference are the cams (Z1 has K20A ITR cams). The K20Z3 (RBC) head has the different coolant port. You can put any of the three heads above on your block (as long as its not K24Zx, which I don't think it would be since it's JDM).