Installing the tappet guide block o-rings without damage is crucial in preventing oil leaks. One tip is to de-burr the cylinder block bores for the guide blocks.
Another is to protect the o-rings while installing them over the guide blocks. Wrap the blocks with a scrap of paper and fold/twist the free ends like a penny roll. Then stretch the o-rings over the paper and roll them over the paper to their grooves before pulling out the paper scrap.
