K-Series Engine Value

[Graham King]

Folks, I'd appreciate a few pointers on the value of the below:

I have recently sold my 1999 K-Series SL. The car as sold had a 210+BHP engine that I had built from a 2nd hand unit that I purchased via Blatchat a good number of years ago. 

I still have the original engine that I took out from my SL and the purchaser of the car has said they would like to buy it at extra cost. However I have no idea what it's worth. 

The engine spec is below:

1.8K SuperSport (140BHP)

Caterham Lightweight Flywheel 

Vernier Pulleys

Original ECU

No ancillaries

The engine had done approx 20000 miles when removed from the car circa 10 years ago. Since then it's been stored covered in my garage for that time period. I'd does turn over freely by hand (socket on crank bolt). 

Any views welcomed. 

Cheers.

Graham

[Wrightpayne]

Graham

YHM

Ian