A year ago I sent my engine to
Barrett Precision in Tulsa, Oklahoma. They were the most reputable engine shop I could find. (Yes I know their website is a bit naff...)
Prior to that I did extensive "due diligence" on every engine shop over here and could not find two actual users who would trust any of them as far as they could throw them.
To be fair, this could be as much a reflection of the poor work done by many as the difficulty of finding past customers to talk to (via the inevitable internet means) but the bottom line is that an engine shop in the USA will quickly get a very bad name if they do any poor work, never mind consistent poor work, because they are so much more widely discussed on the huge American pilot forums, and in pubs like Aviation Consumer.
The drawback of going to the USA is shipping. Air freight is cheap at about £500 each way (for a big engine) but can be appallingly unreliable due to the low grade personnel involved. Been there, done that, and at work we struggle with AF too, time after time, right down to some moronic delivery drivers. Next time I would just use DHL at some £1500 each way and it would still cost no more than a UK job picked up in a van.
The other drawback is warranty, which a US shop would tend to work via a UK engine shop, but the chance of a properly assembled engine needing anything is very remote, and the warranty is 1 year anyway.
I paid $12k+shipping for the same job for which the now-defunct CSE quoted £16k, so the recent moves in the exchange rate are nowhere near making up the difference, and I most definitely could not find two happy CSE customers... and hey how much a warranty from CSE be worth?
If installing to anything other than an N-reg, make sure you get an 8130-
4 form (an FAA Export CofA, a special form signed by an FAA DAR) which is about $300 extra. For an N-reg, 8130-3 is fine and comes standard.
There are some big US firms which can generate an EASA-1 form (e.g. Pen Yan) but their quality reputation is not exactly spotless. But if you have a G-reg on AOC then that may be the kind of firm you have to go to.
The whole engine was statically and dynamically balanced and runs very smooth.
Anybody wanting more info, email me.