Looks gorgeous, faulty engine or not, its certainly worth 4k! Worst comes to worst, get another lump/remove and rebuild, you have yourself a mint cosworth.

You could probs pick up a rebuilt lump for a 1.5k, a weekends worth or work and your laughing. Understandable if the owner is getting fed up of spending money and fucking about with them tho, we all get to that stage. But for someone, there is a great opportunity waiting here.

Good luck