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I’m sticking a new head on this block. Is there any point cleaning the pistons? They’ve done 15k km’s.

Any abrasive cleaning or wire brushing will drop material down the sides and may accelerate wear. You can minimise that by smearing grease around the seam between piston and bores and wiping it out later. However they soon build up a little bit of muck again and then, if the engine is properly tuned, they reach an equilibrium there. Effectively you gain nothing in return for a fair bit of work and risk.

On the other hand any large lumps of stuff can become hotspots that may initiate pinging. You can safely scrape them off with a metal scraper while sucking it with a vacuum cleaner.

TLDR: don't bother

Thanks for that. I’ll give them a clean only because my head won’t be back from the shop until mid Jan and I’ll need some excuse to be in the shed over xmas

Never clean pistons inside the block.

Bit of Ajax and a Brillo pad will make it shine! What's the harm.




(I am kidding BTW).