I have a little dilema that i need the combined knowledge of you locost geniuses to help me decide.

I reckon i am no more than 20hrs worth of work away from completion and IVA. I have currently got a 2.0 blacktop on TB's and emerald K3 ecu which other than a little tuning is running and driving. I have however got a slight g/box leak from between the bell housing and case so the engine g/box has to come out for me to sort it.

This is where my dilema comes in. I've just been offered a complete running st170 engine inc loom and auxiliaries for £250 delivered, (its still currently in the car).
As I am having to remove the engine/gbox anyway should I go for the ST engine, swap everything over and drop that in instead, and run a few extra wires for the vvt. Is the st block the same as the blacktop in regards to the race line sump, alternator, engine mount positions etc etc. I don't want to have to buy more bits if i have to. Or should i just stick with my current set up forget the ST.

I'm not in a hurry to get the car through IVA as without a screen, heater etc its getting close to the wrong time of the year for it anyway. Stoneliegh 2018 will be my target date.

If you want a bit more power then go for it.

Every thing should bolt across but some people have said that the odd drilling has not been tapped. I've not found this.

Not worth the hassle in my opinion. K3 won't run vvt. So stick with blacktop.

It will bolt straight in at the engine level, however you have several options to sort the management.

Change your ecu/loom for either the stock item and swap to a stock inlet manifold and fuel pump/controller.(probably not posssible due to space needed.)
This will give stock power, but a guaranteed way to pass the emissions test with a cat.

Use a vvt delete kit to lock the cam in a fixed position and use your k3/itb's.

The k3 does not support closed loop vvt control that is needed to give a good torque curve, the vvt pro box is specifically for this purpose.
https://motorsport-electronics.co.uk/st170-vvt-control-cams-delete-vvt-pro.html
This will control the cam timing to a target map, and afaik you tune the main management as a normal engine.

Expect 190-200bhp on itb's and a good torque curve with vvt control, and the same power but a peaky torque curve with a vvt delete.

Dave

IVA it as it stands and upgrade after
Trust me on this one

And don't forget the inlet manifolds are different. They will swap over and bolt up, but the ports are out of alignment (so wasting a fair amount of power...)

All fixable.

I have an ST170 in my spitfire. GSXR ITB's and homebrew exhaust as packaging requirements were awkward. But primaries are 26"long so pretty good, however shape is a slight issue. But all that with VVT gives approx 175bhp on the Bailey rolling road. Reckon a better exhaust would give another 10, and a day that didn't have mad temps (my corsa expansion tank started to melt, I kid you not!) probably held another 10 back.

I would leave the blacktop as is and spend your money on cams. Hindsight is wonderful...

get it IVA'd and then have a project for next winter.