Call me insane, but i think for a sapphire, this is my best way to go

For starters, there is the ease of fitment! both are rwd, so mounts and ancillaries will fit no problem (using some sierra parts, like the sump to remove the balance shafts).

Secondly there is the design if the engine. it has bigger valves and ports than the zetec, the bore is 86mm and pin size is the same as a vauxhall. fitting the vauxhall xe pistons (pressure cast ones) would lower the compression height and therefore the CR to a reasonable level. the port spacing is close to a 200sx, so i can easily get manifolds that require little modification to fit.

it is a bit heavier than a zetec, but it also looks to be built alot stronger

can anyone think of a valid reason why i should be taken into 'special care'? or does my argument seem sensible?

 

Sounds good, its your car your choice.

 

Do it. I love i4s. Can't see whyore people done use them. 150bhp out the box on a rs2000. More than 95% of zetecs will ever see.

 

i can see why they aren't used, parts are far more readily available for the zetec, especially the turbo ones. yes the I4 on the rs2k will be around 150bhp, but it's heavy and potential tuning will cost more in the long run.
all depends on level of tune aimed for, i for one have a zetec turbo and yes it wasn't cheap to build, but it's done with good parts and will take decent power.

no reason not to fit one in my opinion, just the tuning potential of the zetec is better due to off the shelf parts and a few tuners out there who know what works to get figures.

 

If its just going to be ghetto spec i say give it a go, but if your spending good money (forged bits) just do zetec as above parts are easier to get.

 

I4 seems to be a very under-rated engine. I've seen a few examples of turbo builds and they seem to work well.

If the I4 had been used by Ford in a few more applications instead of a Zetec I reckon it would be a far more regularly tuned engine.

For the Scorpio engine are you going to run the 16V head from the Scorpio, or RS2000 or make a hybrid with the Sierra 8V head? Supposed to be nice and torquey with the 8V but unsure on turbo builds