Jim, I'm always happy to help. I hate to see people end up with a basket full of broken parts, when it can so easily be prevented. Something as simple to figure as coil bind clearance can baffle people, until they see it calculated one time. Then it becomes crystal clear. And it is a dimension that is extremely critical. When people ask what valve spring is best for them, my answer is always the biggest spring you can fit onto the head, that will provide the closed and open loads required and also offer adequate coil bind clearance.
Back in the days when we were still running 18° heads, a pal was pitted next to us at a points meet. He had a very fast A/SM car. He would make a pass, come back and knock the valve covers off and start shimming or replacing springs. He finally walked over and asked why we never pulled the valve covers off our car. "Why pull them off when there is no need," was the answer. He asked often we changed valve springs on the car and Brian told him we changed them when it snowed. And that was the truth. It was extremely rare to ever have to change out a valve spring. Of course cylinder head and camshaft technology are more Star Wars in nature these days and valve spring maintenance is more common. But when a guy has to either shim or change out a valve spring after just one pass, that is a car with A) the wrong springs or B) springs that are installed incorrectly.
The blown alcohol cars are very hard on springs. Let's face it, the standard Hemi valvetrain layout sucks. And trying to make that stuff live at the kind of RPM levels those cars see at the finish line is next to impossible. Super Stock cam profiles are ultra-aggressive with respect to ramp designs and can be hard on springs. The Pro Stock stuff is so far out of hand, it is ridiculous. Those guys are running valve lifts you would struggle to imagine, with extremely long and large valves and what appear to be drain pipes for pushrods. Then they take that stuff and screw it to the moon, too. I keep wondering when they are going to finally reach a point of diminishing return, by continuing to make everything bigger. Increase valve sizes and valve lifts until a larger spring becomes necessary. The, the pushrod suddenly becomes the weak link and starts deflecting too far. So, you put in a bigger pushrod, but that suddenly puts more mass on the shoulder of the spring. So we now need a heavier spring. And about the time we find a way to build a heavier spring, cylinder head technology makes a big jump. And now, camshafts start growing again and valve mass starts climbing, until we need an even heavier spring, that will end up deflecting the pushrods. A couple years back, we started seeing the physical size of valve springs become part of the weakness of the spring. Remember, a spring is not just controlling a valve, valve locks, a retainer, a rocker, a pushrod and a lifter, it also has to control itself. Talk about a Catch-22! An innovative Pro Stock team tried to develop a pneumatic return arrangement a few years back, to eliminate the valve spring entirely, but physical size was the obstacle. If NHRA would ever allow a 4 valve cylinder head, where you could bring valve sizes back down and use pneumatic returns on the valves, you will see a quantum leap forward in HP. Some newer materials are allowing physical valve spring sizes to be reduced, which is helping the problem, but it won't be long before the smart cookies will start having problems there, as well. Race springs were up in the 1.750" diameter range and are now back to a point where 1.550" diameter is pretty large.
A (then) pretty well-known race team from the Indianapolis area had pulled out all the stops to build a no-holds-barred, damn-the-budget, full-speed-ahead Comp car. After a few races, their crew chief came to me, wanting help on trying to get his valve springs to live. It was like passing a Secret Service security check, but he finally allowed me to look under the valve covers, to see if I could spot anything wrong. Within seconds, I could see what was wrong. He had an 18° cylinder head and was running a standard 23° valve cover. The valve springs were getting into th4e valve cover and beating themselves up. You might think a steel valve spring, doing a ritual mating dance at 9,000 RPM would have its own way with a cast, aluminum valve cover, but that is just not the case.
I can remember running valve covers with pockets at the top to clear the tops of the rocker arms and pockets at the bottom to clear the valve springs. We would get stuff moved so far apart, we would lose the valve cover mounting holes. We had one set of valve covers where we drilled the Jesel rocker arm bar and ran two long studs up through the very center of the covers. A well-known race engine builder saw what we had done and asked if we were running modified polyspheric 318 Chrysler cylinder heads. :rofl: It looked odd, but there was no other way to hold the valve covers on.
This video is old as the hills, but take a look at a valve spring on an old Cup engine running at 7,000 RPM on a Spintron -
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Can you imagine coils deflecting that far? Get that engine at the right RPM where the spring wire resonance gets into some bad harmonics and LOOK OUT! :wow:
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Back in the days before YouTube, we had a Spintron video of a spring that was going wild with harmonics. It set up a wave that would travel down the coil to the cylinder head, where it would reflect and travel back up the coil, reflecting off the retainer and back down again. RPM got bumped up a couple hundred and suddenly, there were two waves, moving in opposite directions. Well, there were two waves until they ended up meeting one another, when the spring fractured.
