By Joe Mondello
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!
Some engine builders also have the theory that machined green blocks, when assembled and run, will relieve their own stress; especially in the fields of drag, circle, boat, and Bonneville racing. My extensive testing proved time and time again this is simply not true. One of my mottos is “machine it straight, keep it straight – machine it round, keep it round”. Most shops cannot do this using old school technology. The most amazing thing I found is how much I helped the 5 HP Briggs & Stratton flat head Kart engine on Methanol and running on a dirt track. That engine is the most expensively built, unstable one that I’ve ever seen but I shook it and cryogenically froze it fully assembled (less the magneto and rubber seals) using the same material and thickness engine base plate as OE. It includes the side cover and gasket, head and gasket, fasteners and gaskets, all torqued to specs as a final assembly. I shook the assembly first and then put it in the freezer at minus 300°F before bringing it up slowly to + 275°F for the heat treat cycle. After doing so, that engine lasted a full season without a rebuild!
I have built a lot of engines in my “hobby” job of 52 plus years and shaking with freezing have been two remarkable breakthroughs in high performance or even for stock engine building for quality shops. The most remarkable part is the shaking, as it changes sizes. Therefore never shake after the final machine work is done. You can freeze after final machining but in my opinion it is better to do the work after both processes. That way all parts are free of stress and one to two points harder on the Rockwell C-scale. Also note the surfaces have more lubricity in them for easier machining. Always have your mains torqued when freezing or shaking. Do not freeze aluminum blocks with the sleeves in place; freeze the sleeves separately. You can, however, shake it with the sleeves in place.
I have made some really trick fixtures for shaking components like rods, cranks, valve springs, etc. On our valve spring fixture we can install up to 16 springs and retainers adjusted to the installed height for each application, shake them, and then place them into the freezer without disturbing the fixture. We do the same process with my rod fixture. Cranks are shaken parallel to the shaker table, but we stand them up while they’re in the freezer. Heads are bolted to the table with a head gasket between head and table. Blocks are bolted to the table with the bell housing down against the table. We usually shake four blocks at a time; one in each corner of the table. To shake pistons we run a steel rod through the pin holes with tangs to the table; four in a row and clamp them securely to the table. Always remember, when shaking parts they do get smaller and freezing does not affect the size of anything. If you only have one choice due to cost, always choose shaking instead of freezing. Of course, shake and freeze is the ultimate procedure as we’ve increased valve spring life more than 300%.
I once froze a set of Childs and Albert aluminum rods in the ‘90’s for my VO Twister Oldsmobile R&D race car. Everyone is told to expect to run this type rod 150 to 250 quarter mile rounds; mine ran 1,159 rounds down the track and driving back to the pits before one broke. So you see, I really believe in the shaking and freezing! Most people do not use aluminum rods for street, Bonneville, boats, or circle track because they have cycling memory. I have applied frozen aluminum rods in all the above applications with great success.
There are many things in this industry that are hard to sell such as internal and external engine coatings, nitriding cams and cranks, stress relief shaking and cryogenically freezing. . .well guess what? Nobody flew until the Wright Brothers tried it and look where that industry is today! Far too many engine builders, and I mean even good ones, are not thoroughly convinced about my shaking/freezing techniques. I have taken a lot of aftermarket blocks and heads, both cast and aluminum, and stabilized them with this procedure, making them much better components. I am still trying to convince some builders and manufacturers that stress kills engines just like it does people.
Shaking and freezing doesn’t just start or stop at the engine either. Stress relief shaking and cryogenically freezing engines and their components started in the early ‘60’s when the Bonal Company in the Midwest first started experimenting with it. In 1962 Stress Relief Engineering designed their “Formula 62 Loadmaster 2000” to relieve sprint car parts and components. They actually welded the car chassis together right on the shaker table as it was operating. The chassis would run several seasons without having any cracks appear in the welds. Metalax makes a stress relief shaker unit today. You can remove stress from virtually anything out there that is manufactured. Some interested engineers and chassis builders, like NASCAR, have purchased units and started shaking their engines, drive trains, and brake rotors and related parts. They also shake weld the chassis to eliminate fatigue cracks. This process along with cryo freezing for years was one of the best kept secrets of racing. I purchased my shaker table 26 years ago from a southern California sprint car chassis builder who designed this vibratory 62 table in 1962. Shaking is a must in all my performance built engines and chassis components. In the early 1900’s a Polish machine gun company started freezing firing pins because they were soft and breaking. They used ice and nitrogen on some but did not have total success due to nitrogen brittlement, because they submerged some of the parts in it. In the new cryo machines like our Texas made in the USA unit, the nitrogen never touches any parts. I have used my cryo freezer for over 20 years and we love it. We have frozen carbide valve seat cutting tips and porting burrs, drill bits, broaches, brake rotors, golf balls and clubs, gun barrels and parts, gears, trannies and differential, axles. Most likely we have frozen every engine part imaginable, even spark plugs. I have never seen any ill effect on anything by using the freezing process.
If you do a lot of aluminum head and block repair, undoubtedly you have experienced a dropped valve seat. Stress did this. I learned years ago from the best aluminum welder on this planet Quincy D. Epperly. He used to repair blocks and heads for Rodec, Venolia, Alan Johnson, John Force, and probably everyone else in top fuel who insisted on a perfect repair. He always heated up the part and peened every weld he laid down with an air hammer. He told me, “If you don’t peen the welds there will always be stress in every one of them.” There’s that dreaded “S” word again!! Then, after he welded he shook all his parts on the stress relief table. You could not tell one of his repaired blocks from a new one. Quincy died in 2001 and with that we lost a truly great innovator and craftsman in our industry. Any time you get in some heads, aluminum or steel, that have been previously welded and some seats fall out – stress did it.
You can learn a lot from pros who have been around a long time and become icons in this business. They are living legends to the industry. Not only can you be like them, you can use their information and take it a step or two forward by trying new things, innovate! Change your ways, step out of the forest and look at the trees; think outside the box! Remember, stress kills everything so take my advice and relieve the parts to relieve your mind! I hope you have enjoyed my article.
Engine professional Magazine 2011