Get more power, torque and component longevity
Stress is a situation in everyone’s life and unless that stress is relieved, it may kill you. I have lost a lot of friends from stress-related illnesses and it can affect your engine in similar ways. The same is true with other components in a performance piece. When stress is relieved, all the parts become much stronger and more reliable, just like with people. Every part that is cast, forged, or is a billet has inherent stress in it and until that stress is relieved, the part remains unstable.
New cylinder blocks, heads, cranks, rods, valve springs, pistons, and oil pumps have a lot of stress in them. These components will move around after you’ve machined them and built the engine unless you stress relief shake them. For this reason, many engine builders prefer to use previously run seasoned blocks and components because they feel the stress and possible movement of the block and heads is no longer there. Well, not all the stress is gone and I had to prove that to myself, too, before I was a believer. So, I took an Oldsmobile block that had about 150,000 miles on it and measured everything; then put it on my Stress Relief Engineering Vibratory 62 Load Master 2000 shaker table and gave it a massage for about 2 hours at 100 hertz frequency and guess what I found? It still moved around significantly. The total deck changed .003”; the bores .0025-.0035”; the main line .001”; and cam tunnel .0005”. These measurements show that everything shrunk significantly from prior measurements. This observation blows the theory out the door that older components are stable, maybe more so than new but not quite there yet!