Engine Builder Shop Solutions: October 2009
Valve Spring Clarification
There are many misconceptions on the visual inspection of valve spring free heights. There is a manufacturing tolerance on this dimension. The spring can change during the heat treat processes and squareness during the coiling process. Spring dampers can also influence the free length as they are installed before the spring is packaged.
Here is what is important:
Always check the valve spring tension at the manufacturer’s installed height spec (e.g., 141#@ 1.750˝). This specification is the value they target during the manufacturing process and has a tolerance of +/- 5%. This percentage value will change when manufacturing higher load and multiple assembly springs. When purchasing a set of high-end springs each spring assembly is checked and then is matched as a balanced set. These high-end springs still have a +/- percentage during manufacturing but are sorted for the best possible balance.
Using this information you can receive a set of springs and follow the procedure to verify the load is correct and not feel there may be an issue because of the (relaxed) free lengths are not exact from spring to spring. Also it is a good idea to calibrate (certify) your spring tester frequently.
Grand Rapids, MI
Protect Your Investment, Customers, Warranties and Your Business
One great way is to use an engine dynamometer or engine test stand to test and break in engines before they are installed or delivered to another facility for installation. The dynamometer ensures the engine is broken-in properly and there are no problems before it is delivered or installed. This of course is extra time and labor intensive but the rewards are fewer comebacks, which can mean more dollars in your pocket.
Dynamometers are expensive, of course, but unless you are a pro race engine builder, manufacturer, or a really rich guy you may not need a full-blown model. With a little time and money, and ingenuity, you should be able to put a nice functional engine stand together yourself for some of your more popular builds. After it is put to use watch your comebacks fade away.
Engine Pro Technical Committee
Clean Dishes AND Engine Parts
How to make your engine parts clean enough to eat off of take an old dishwasher, some Cascade dish soap and a little flash rust powder to pre-wash pistons, rods, valve springs and other small parts, instead of spending the time to wash them by hand. Just load the dishwasher and walk away!
Proper Fastener Preparation
In order to obtain proper torque (or torque to yield) values, it is absolutely imperative that threaded fasteners are clean and in good condition. All threads should be inspected and cleaned, especially fasteners and threaded castings or housings that will be reused. The best way to insure that threads are in optimum condition is by utilizing thread restoring tools. These tools are designed to clean and restore existing threads, not to cut new ones.
Most typical tap and die sets are designed to cut new threads and their ability to remove material is detrimental to used threads. Male and female threads found throughout the automotive industry have approximately 75% contact between the threads and using a tap and die set will very likely reduce this contact percentage further by removing necessary material from the fastener and/or the threaded receiver. This reduction in mass will affect torque values and ultimately the ability of the fastener to maintain proper holding properties.
Thread restoring sets can be obtained from most, if not all, of the major automotive tool suppliers and are a valuable addition to any tool collection. Finally, all blind holes most be free of residue and all threads and contact surfaces should be lubricated sparingly with clean oil or assembly lube.
Twin Lake, MI
Tarp Strap Dampener
To keep chatter and harmonics to a minimum on a resurfacing machine, attach a tarp strap to the head or manifold. Then stretch the strap and hook it to the machine. Any vibrations will be countered by the rubber tarp strap.
NAPA of Saratoga
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