Don't we know it! We maintain a small fleet of Plaxton bodied Dennis Javelin nails with the 6 litre ISBe Cummins enigne in. They have a habit of cracking exhaust manifolds which means you're in and out of it like porn stars cock as half of it you have to do from inside and the rest outside, but you end up doing a bit inside then out, then back in, then out agin....