Hi,The images look more like an exhaust manifold rather than a heat exchanger.
The narrowing in the first image looks more like metal than calcification. Would an experimental scrape show one way or the other?
Hi Richard, thanks for your response. I have done a bit and seems quite solid. Prob leave it be!It does look like an exhaust manifold / water injection point. It looks to be in reasonable nick to me but, as TCT says, a bit of judicious scraping would prove conclusive.
Richard