High performance low mass valve spring option vs XE282 roller cam

[CCH]

For those of you running high lift hydraulic roller cams with a radical lobe shape, you know that keeping the roller on the lobe over 6K can be a frustrating task. Hydraulic roller lifters are heavy. Large valves are heavy. Double or even triple springs add a lot of mass that has to reciprocate up and down with valve actuation, and the corresponding retainers carry a good amount of weight as well.

At 6500 RPM, all of the weight of a lifter, pushrod, retainer and locks, spring coils and the valve itself have to rapidly open, then change direction and slam shut more than 58 times every second. All the while, the lifter needs to keep in constant contact with the lobe - quite a task. You can't make reliable power at higher revs when the valves start to float.

There are many aggressive lobe profiles available for our engines, and they can make great power if you have the right components to support them. On the 334 CI engine I'm currently assembling, I'll be running a common roller cam choice for SBF strokers - the Comp XE282 roller. This cam has some very aggressive lobe profiles, and I've been told by a few people including my machinist that it's not an easy task keeping the larger XE roller cams from floating valves on the dyno. These are also SADI/cast core cams and not billet, so many will suggest limiting the amount of valve spring pressure. The recommended max amount seems to vary from source to source, but I've found mention of everything from around 400# on the nose to 550#. I know people running in excess of 450# open pressure on these without damage, but I'd rather err on the lower side if I can do so and still get the RPM I'm looking for.

If you are trying to control float but are limited by how much spring pressure you can run, there are only two other parts of the float equation to modify - the cam lobe profile or the mass of the moving parts. As I already have the cam, I opted for the latter. Unfortunately, the double springs and hardware on my TFS heads were not exactly lightweight. The pressures were significant at 125# on the seat and around 370# open, but the mass of these 1.470" diameter springs/retainers needed some help if I expected to get any kind of float-free RPM out of the motor.

The most important place to remove weight from a valve spring assembly is on and near the end that has to travel the most distance during valve actuation. If the base of the spring is heavy, it matters little as it doesn't have to move. Conversely, if the top end and retainer are heavy, that has a negative effect on float due to the springs having to overcome the inertia of greater mass when trying to close the valves. There are multiple schools of thought on how to improve this.

You can always decrease weight by decreasing size. Going to a smaller diameter spring accomplishes this, as does reducing the diameter and thickness of the retainer. Spring diameter can either be reduced down the entire length of the coils or can taper down toward the top of the spring (the popular conical or beehive designs). Either way, mass is removed from the end of the spring that has to travel the furthest during valve actuation. The smaller diameter retainer can remove a lot of mass as well.

Changing materials is the other way to reduce mass. Most notably, substituting a metal like tool steel or titanium for the usual chromoly on a retainer can provide a substantial reduction in weight. In the end, I decided to do both. I wanted to employ a smaller diameter spring in addition to lightweight retainers, but also wanted to get the most for my money. In the end, I was able to assemble the valve spring upgrade for about $330 including locks, seals, locators, double springs and titanium retainers. The catch? Not much, unless you have an aversion to running "GM-oriented" parts on your heads. The parts used for this are generally used on LT and LS engines.

It's nothing new, as before the dawn of readily available aftermarket SBF heads started to hit in the late 80's/early '90s, the most common head improvement was a good port job and the installation of larger Small Block Chevy valves. No they didn't flow like a set of 205 Renegade AFRs, but short of Cleveland heads and a custom intake, they were about all the average guy to afford to do to improve Windsor breathing substantially. -Plus, how many Ford 9" rear ends have you seen in other makes? Those LS springs are hidden under valve covers anyway...

There are a couple companies that will sell you 1.2-1.3" diameter spring kits for your SBF. I looked into these, and I have no doubt that the people at those businesses know what they're doing and can offer some great guidance and advice regarding spring selection for your cam and head combo. Most of them end up in the $400 range for a full kit that includes steel retainers. By most accounts, they work great and the purchasers are happy. I'm certainly not here to disparage any of those providers. In my case, I already had an idea what I wanted for rate, installed height, bind clearance etc., and set out looking for a match that met or exceeded my needs for less money.

Eventually, I decided to get my parts from Brian Tooley Racing. BTR is a major aftermarket retailer of (primarily) GM LS performance parts - particularly valvetrain items. While I haven't talked much with Brian in many years, I originally met him back in the mid '90s. I was doing fuel injection and engine control product lines for Tomco and Brian was working for Holley in Bowling Green, Kentucky. His project at the time was as the main development force behind the Systemax products for the 5.0l Fords. He's a sharp guy, and though he makes a lot of LS money these days, he's far from a Ford hater.

BTR and a few other companies sell retainers that work with small diameter LS style springs, yet accommodate a valve stem of 11/32". This is important, as SBF valves are 11/32" diameter. Those of us who put a set or two of Small Block Chevy valves in Ford heads back in the day also know that SBC valves are also 11/32". LS valves are 8mm by the way, so standard LS retainers will not work with standard SBF/SBC valves. Problem one solved, I had a retainer that would work.

I chose a set of double springs with a diameter of about 1.3", already a reduction of about .2" diameter from the original springs and a retainer that was nearly 1/4" smaller diameter (and titanium). The locks used were standard size/style 7 degree single groove. I chose a set of Comp Cams 648-16 machined steel locks. The rate gave me a little over 150# on the seat at 1.78" and around 400# on the nose.

As these springs locate on the inside diameter of the inner spring, a locator shim was necessary to keep them centered and add reduce some of the installed height. Selection of the locator will vary depending on the diameter of your valve guide, but the guides on my TFS heads was .5" all the way down. I chose a locator that fit the correct I.D. of my inner spring, and also had a .505" hole through it that fit perfectly around my .5" guides and kept it from moving around. Valve seals were standard .5" teflon or viton push-on seals. As long as they clear your inner spring sufficiently, they'll work.

The trick to making this combo work (other than the use of 11/32" retainers), is getting an installed height that works. Compared to SBF retainers, the LS retainers will end up placing the top of the spring a little higher on the valve stem. This will lead to an installed height that comes out to roughly be about .065-.075" greater than with the old retainers. Your results may vary depending on tolerances and the fit of your old locks and retainers.

On my TFS heads, I was at 1.78-1.8" installed height before. This included the .060" thick spring cup included with the heads as well as one .030" thick shim. For my initial mock-up measurements, I kept both the spring cup and existing .030" shim, and added the .060" thick locator for a total shim height of .090". Much to my satisfaction, this was not at all far off the mark. I ended up with installed heights roughly in the 1.85" range - right in the ballpark to correct with a little bit of shim work. I only got the chance to check one intake/exhaust pair before heading out of town for work, but I intend to finish them up this weekend. At least I know that they're close enough to get what I need out of them.

The biggest smile out of this whole project so far was achieved when I weighed the old versus new valvetrain parts. I'll include pictures, but here's the highlights:

Old valve spring weight: 117.56 grams, old retainer weight: 32.42 grams
Total of both: 149.98 grams

New valve spring weight: 92.9, new retainer weight: 9.3 grams
Total of both: 102.2 grams - a reduction of nearly 50 grams, and only 2/3 the weight of the old setup!

I will also be freshening up the motor in my other Mustang at some point in the next few years, and absolutely plan to do something similar on those heads as well.

As a related note, some may question "why not run beehives?" I have no hate for them, and the physics is sound for the same reason that my current combo is an improvement. In fact, depending on spring and retainer diameter up top it's sometimes possible to get even greater mass reduction with some conical and beehive setups than what I achieved. I just prefer the extra safety margin of the inner spring should there ever be a valve spring failure. Beehives and conicals can only run one single spring, no possibility or a double or triple configuration. If that one spring breaks, your chance of dropping a valve is arguably higher than with doubles.