Hello, please I really need help.
I have swapped the engine block of my mk2 1242cc yr01(mpi) model to a mk1 one(spi).
I have managed to put the knock sensor under the inlet manifold. The mk1 pistons and shell bearing dimensions are slightly smaller than the mk2. The mounting was ok, with swap of pulleys. The engine starts with no problem, engine light too is off
My problem is that the car HAS LOST POWER DRASTICALLY,EVEN WHEN I'M ON SECOND GEAR, IT HAS BECOME SLUGGISH.
PLEASE HELP.

is the Timing all good?

aint mk1 and mk2 on differnt timing marks,?

Check the timing, but

The mk1 pistons and shell bearing dimensions are slightly smaller than the mk2

Click to expand...

is rather worrying.

It might be loosing power due to poor compression (pistons too small) or be on the point of seizing (shell bearing dimensions too small).

Generally it's a bad, bad, idea to swap components over from one engine to another without measuring and machining: for example, even given a new set of pistons and rings with manufacturer's sizes clearly stamped on them, no-one would bore the block without first measuring them several times.