The OLDER flushes were very harsh and did take away the carbon deposits so fast it came away in chunks and did damage things.
Modern flushes like Wynns are totally safe, and do work 100%.
The flush like wynns does not take away any lubricant properties at all.
I use 1 can of wynns prior to a engine change, but don't use it the way wynns state.
I put it in and drive for 200 miles before changing the oil at 12,000 miles, or 1 year old.
Has worked for me for around 25 years, my engine has just been rebuilt after 200,973 miles, and it certainly isn't a pampered car engine wise, I didn't buy it for that.
You will be perfectly safe with a decent flush like wynns, but it is possible that it may get noisier as it dislodges years and years worth of crap, but this should settle.
My engine was spotless inside when stripped, didn't even need washing in the hot tub at the engine shop, all oil passages were totally clean.
A problem with the cossie is the collection of congealed oil that collects in the oil feed galleries each side of the head at the rear esp on the hotter exhaust side, when this is broken down it could potentially jam a tappet hole at worst.
So the risk is yours, it's perfectly safe if it hasn't had a lot of missed oil changes, crap oil, most detergent packages in modern oils are excellent and there won't actually be much carbon build up, it's held in suspension in the oil, hence the oil going black so most comes out with oil changes.
I flush before each oil change myself on every car, astra has 237,000 on it now.
tabetha