Many motors are now well into their 30's in terms of age, let's look closer at the side housings of one 13B that came into the shop for a refresh.

This was a 1988 GTU 13B that was well taken care of, sat for awhile and now compression / power loss have taken over. 

This side housing clearly tells the story of corrosion yet minimal wear. When we write about how motors come apart, this is part of the process to understand, clean, measure and get motors back to specs. 

This motor had coolant leakage into the chambers, look at both the water jacket seal and the groove. This is typical of a motor that wasn't run and sat without heat cycles to keep materials fresh. If you don't clean, examine and identify these issues on your rebuild, it will come back to bite.

We see this on older motors, what do we do about it? I happened to have a solid spare rear housing to replace it with. If reused, it would have soon been eating coolant and pushing towards an early death. Not acceptable. 

Can you fix these issues, is there a process that is proven? Everyone will have their opinion, my experience is that it is important to do it right, that means replacing it. Yes, that does take time, however as I tell my customers, I do not want to see the inside of this motor for a long time. Racing or street performance, it doesn't matter.