TonyHawk

I have an odd problem that I just can't track down and I was wondering if anyone on here has come across it, or maybe had some suggestions I could investigate? The long and short of it is, I have an exhaust smell coming into the cabin and I cannot find out where it's coming from? A bit of history: I have a 1985 Daimler Double Six 5.3 V12; I have had the engine out and rebuilt it, swapped out the injection system for Weber 40IDFs, high lift cams, new valve guides, multi-angle cut valve seats, light skim, branch manifolds, manual gearbox conversion, high ratio rear diff, electric water pump and fans and a Electromotive ignition system (replacing the distributor). As the carbs have no option to plumb in the crank breather, I have it exiting under the car, by the rear axle. When stationary, I can stick my head in the engine bay and sniff as much as I like, but I cannot smell anything. When driving, with the windows closed you can't smell a thing, open the window and it's there (As the engine warms up, the smell is more noticeable), but not hugely strong, however there and when I get back, my clothes smell of it. There are no oil leaks in the engine bay, no exhaust leaks and no cracked gaskets (all exhaust gaskets are new as of 2 weeks ago). There is one small leak from the rear crank end cap, but it's minute. If it were that causing oil to leak onto the exhaust, then how would it get into the cabin, via the drivers window, even on the motorway at 80mph! If it were the crank breather, again, being at the back, underneath, how would this find it's way to the window? I'm at a loss, I cannot find anything? Any help or suggestions would be very much appreciated. Thanks