The old inlines were/are good engines. They are not the best to hotrod because of their crossflow design. They run very smooth. The only problem I know of is the decaying of the insulation of the wiring harness. But that happens to almost all old Mercs. The only other drawback is the way they are put together. You have (or are suppose) to install the complete rotating assmebly in to the block all at one time. Never done it, but from what I have seen, it is not the easiest thing to do, especially w/o special tools.