AsmodeusXr

I have a 2000 civic si with a non stock engine in it, which I've had no luck thus far with identifying. I am somewhat new to cars, and this is my first, so please be patient with my ignorance when it comes to the vernacular.

All I know is that the engine is much smaller than stock, taking up about only half the room. It is engraved with the following on the front:
HM (in larger, bolder lettering than the rest)

ZC
6603103

3(again, bolder font)

Any ideas?

civic402lx

Post a picture.
look at the block, get the engine code.
dont know how or where to find engine code?
Google it

JRCivic1

A "ZC" is a Japanese engine (JDM) and is NOT what came in a USDM 2000 Civic Si. Have you run your VIN code to see if in fact your car is actually originally a Si chassis ??? If so, then someone has swapped in this inferior engine and you have been had... unless you bought this car for pennies on the dollar.