Valve springs are one of the hardest worked, but least understood parts on any engine. And while a lot of engine parts, even the cylinder heads, might get replaced during an engine’s lifetime, the valve springs from the old heads will most like just get transplanted onto the new ones.
Make no mistake, though: valve springs, like every other stock engine part, weaken over time. That means if you’re planning on making any kind of engine modification that’s going to increase RPMs, pushing stock valve springs beyond the point they were designed to function is guaranteed to result in parts failure.
The solution is easy: install new valve springs. There’s more to valve spring selection, however than just getting the biggest, stiffest springs you can find. You have to select the one that matches your application; and more importantly, they have to work in harmony with all the other parts on the top end of your engine.
Choosing the Right High Performance Valve Springs
Although the search for horsepower typically means making things bigger, balance is infinitely more than size when it comes to valve trains. That’s why the correctly sized, high-performance valve springs available from the aftermarket are so integral to controlling the valve train, and why your camshaft specs and RPM range are so critical for determining that size.
Valve springs have two jobs: the first is providing pressure at all times to keep the valves closed, and the second is ensuring that there’s also sufficient pressure at all time on the rest of the valve train to open them. It’s this double-duty, however, that makes the balance in valve spring performance so important.
On a high-performance turbocharged engine pushing 8500 RPM, each spring could be pushing this balance up to 140 times every second, and by choosing the right sized valve springs, you get the benefits of:
· Correctly timed valve openings and closures at all RPMs;
· Reduced wear on valves and valve spring seats; and,
· A reduced likelihood of valve train breakage or engine damage.
Regardless of whether you’re looking at OE replacement automotive valve springs for a mild daily driver Barra, or competition-level valve springs for a 1JZ brute, the same benefits still apply. There’s free horsepower available just by using the right valve springs, and that makes installing the correct ones for your build one of the most important valve train decisions you’re going to make.
How to Recognize the 3 Main Types of Valve Springs
High-performance valve springs, including shims and valve retainers, are sold in sets to match the number of valves your heads have, and the lift profile of your camshaft. There range of profiles is extensive, but there are really only 3 main types of high-performance valve springs:
· Single coil. These are the standard, cylindrical-shaped, one-coil valve springs used in stock, and mildly modified engines. They’re limited by heat, friction, and the amount of lift that’s possible during high-performance use.
· Dual coil. These cylindrical-shaped valve springs use two coils instead of one, and are preferred for high-performance engines. They provide extra damping at higher lift, and can prevent a valve from dropping down into the cylinder in case one of the springs breaks.
· Beehive. These taper-topped, one-coil valve springs are tighter at the top than other types and are another high-performance engine favourite due to their lighter weight, higher allowable lift, and greater resistance to floating.
And because of the job they perform, it’s also no surprise that titanium and ultra-high tensile strength steel are the preferred materials for high-performance valve springs over OE carbon steel variants. Their resistance to fatigue and sagging are qualities that high-output engines need for reliability as well as performance.
Know Which Spring Specs Match the Engine You’re Building
Assuming your valve springs’ diameters don’t come into unintended contact with other engine components, there are 3 crucial specs that need to be considered when you’re picking them out:
· Spring height. This would include the installed, open, and fully compressed (binded) height of the spring.
· Spring pressure. This would include the amount of pressure needed to open a valve all the way, along with the amount needed for it to stay completely closed.
· Spring rate. This is the amount of force needed to compress a spring, expressed in lbs/inch.
If you’re only rebuilding a stock engine with stronger internals, manufacturers can provide you with these specs. And if you’re building strictly for a big boost in horsepower, your camshaft manufacturer is best prepared to advise you about which springs are going to work best with their cam profiles.
Again, balance is the main objective, so it’s important to remember that even small variations are going to make a difference in performance. Ultimately, knowing which characteristics you want your engine to have will help you choose the right valve spring, without the problems and risks that can arise from using the wrong ones.
The Dangers of Neglecting Your Valve Springs
Although the range of problems that can happen on any engine with insufficiently rated, or overrated valve springs are consistent, you can expect them to be more severe when racing valve springs are involved. The 3 main problems that are encountered when using incorrectly sized valve springs are:
· Coil binding (when the height of the fully compressed valve springs won’t allow the valves to open completely);
· Over stiffness (when the camshaft is unable to compress the valve springs enough to open the valves completely); and,
· Valve float (when valve springs don’t have enough pressure to hold a valve closed).
And while any of these situations will inherently lead to excessive heat and friction, there’s much deeper damage taking place. Premature wear on the camshaft, lifters, and pushrods is also taking place, and you’ll experience it as:
· A significant loss of compression and performance;
· Engine misfiring and backfiring; and,
· Excessive valve train noise.
In short, if you’re building for reliable high-performance, you have to invest in the right high-performance parts. Reusing stock valve springs, or forcing inadequately rated springs to perform outside of their range can ruin an otherwise perfectly built engine. Fortunately, when it comes to high-performance valve springs, Australia has resellers who know precisely what you need.
The Final Word
At the end of the day, the amount of horsepower your engine is capable of producing is going to dictated by how well your valve train performs. If you’re upgrading camshafts, lifters, and valves, neglecting to upgrade your valve springs is going to cost you power and reliability.
Making sure to install properly sized and rated high performance valve springs on your next rebuild will let you get every ounce of available power out of your valve train while ensuring it stays balanced. It’s the easy way to prevent premature part failures at the top end of your engine, and you’ll immediately notice the difference in performance.