If the oil has already been drained from the engine, try to arrange to remove the sump pan. Inspect the bottom-end for signs of wear and any stray metal particles. If you're still feeling keen, you might want to remove the valve cover(s). You'll soon discover any residual "mayonnaise", obvious valvetrain wear (eg in rocker arms) or excess oil gunk build-up. The "black death" of this Mazda V6, for example, was a good indication of poor oil quality.
Next to come out should be the spark plugs. Inspect them for any abnormalities such as oil dampness, baked-on black deposits, or even the wrong plug-gap. A white electrode surface indicates lean mixtures, engine overheating or the incorrect plug heat range. A physically damaged spark plug often points toward detonation. Stay away from an engine with damaged plugs.
Furthermore - if possible - you might want to take off the pressure plate to check out the condition of the flywheel and clutch. Be on the lookout for flywheel scoring and cracks and a thin, fried-looking clutch plate. You'll find this on any high-performance AWD car that's had a semi-hard time.
If you want to get really tricky and blow the wrecker away, you can hire what's called an endoscope. This is a very small camera (4.3mm in diameter) on the end of a flexible stem. The end section can be bent so that the camera (which has its own light source) looks up at the underside of the valves or down at the top of the piston. National company Tech Rentals (
www.techrentals.com.au) rent endoscopes for around $305 a day - if you're looking at a mega-dollar engine it's be a wise investment. (Plus imagine where you could go looking with such a small camera? Well, maybe not.....)
A compression check is almost impossible to carry out on import engines - except for those in half-cuts where you can easily insert a battery. If it is possible to turn the engine over, connect a compression gauge and look for consistent readings across each of the cylinders.
If you plan on using an import gearbox, it's a good idea to remove the oil pan (or plug) and - again - inspect the fluid for stray particles. As with an engine, perform an external inspection for leaks and signs of being pulled apart. If you're planing a FWD transplant, make 100% sure you can get driveshafts to suit your application
Turbos
When you buy a hi-performance Japanese engine, a turbocharger - at least one - is often part of the caboodle. Short of fully stripping a turbocharger apart, you cannot obtain a sure-fire indication of how healthy it is.
Bill Keen of Adelaide Turbo Service suggests a few easy assessments to quickly identify a dud turbo. Interestingly, Bill has seen a l-o-t of ex-Japan turbos that have been below par due to too few (if any) oil changes. We're told it's a good idea to remove the oil drain fitting from the turbo core and check for sludge or carbon build-up. Interestingly - despite common belief - it's not always a good sign to have minimal axial shaft play. This can in fact mean that there's an oil/carbon build-up that's making the shaft feel tight. On the other hand, Bill considers too much axial play to be when the wheels are touching (or very near touching) the inside of the housing. It's also quite common for the 'lads' in Japan to run their turbo cars without an air filter - this may have led to damage on the compressor wheel, which may be visible by using a torch and careful inspection.
Important Final Bit!
Having performed these inspections, make sure that you get all of the details of the wrecker's engine warranty. Also, ensure that any deals - no matter how seemingly insignificant - are made in writing. This should cover your bum unequivocally.