Guide to Hydraulic Valvetrain
 

When setting up a valvetrain, power comes from a system that is well designed and in control. Such a system is typically more reliable, and for the vast majority of street/strip cars, having a valvetrain that simply works for 25k miles or so without constant adjustment is what you want. But you also want power. Control can be had with super aggressive combos, which might make power, but at the expense of longevity. It’s a trade-off; one that doesn’t have to occur. Why? Because you can setup the system to be reliable and perform. And here is how.

I generally recommend two rules when setting up a valvetrain as a “system”: light as possible over the valve side of the rocker and stout as possible on the lifter side of the rocker. See Figure 1.


https://cimg2.ibsrv.net/gimg/ls1tech...2c4c3b18ec.jpg
Figure 1. Valve Side Highlighted.

Valve Side Recommendations

When I talk about lightweight over the valve side, I mean everything on the intake valve side of the fulcrum on the rocker arm. That includes the tip of the rocker arm, the valves, and the valve springs. When I say stout on the lifter side, I mean the lifters, pushrods, and pushrod cup. Both will be affected by cam lobes, which I will get to momentarily.

For valve side of the fulcrum, a lighter setup is easier to control, even with aggressive lobes. It requires less spring pressure for a given lobe and more easily revs. I typically recommend lightweight, hollow-stem valves for the intake valve, and solid stem valve for the exhaust. The weight is similar between the two, due to the size difference, but the added material helps the exhaust valve deal with the heat a bit better. I also recommend either lightweight dual valve springs with titanium retainers or beehive springs. Modern, nitride beehives have similar closed pressure to lower-end duals, but weigh much less, have better harmonics, and typically control a valvetrain to a higher RPM than a similar spec’d dual. However, some lobes or valvetrain combinations need the added spring pressures of a quality dual spring.

The rocker arm is a place where the moment of inertia or MOI can wreck the entire valvetrain setup, because an extremely heavy rocker is difficult to control, requiring additional spring pressure to achieve the same RPM potential as lighter options. One example is the stock steel LS1 rocker is very light over the nose of the valve, but aftermarket aluminum roller rockers are not. Even though they are aluminum, the added weight of the roller bearing, pin, and additional material to withstand the stresses of high valve spring pressure makes them less than ideal in certain applications. Further, the added weight requires more spring pressure than the stock, steel LS1 rocker, but, as we have seen in past failures, the aluminum is sometimes unable to take the added spring pressure without fatigue and failure. Currently, there are no perfect solutions for the LS1 – either scrub the valve guides due to side loading at higher lifts with the stock rocker or add more spring pressure to the system, adding friction, weight, and fatigue to an aluminum roller rocker.

I typically use stock rockers with upgraded trunions to handle cam lifts upto .630″ with 1.7:1 ratios per Brian Tooley's recommendation. Bronze guides scrub easier and may require roller rockers. In many cases, you can have the head manufacturer install powdered metal guides, which take the scrubbing action of the stock rocker arm without as many detrimental affects.

Lifter Side Recommendations

On the lifter side, you want a lifter that can adequately hold the spring pressures applied to it. Any decent lifter is all you need, but I generally like short-travel lifters with link-bars. Link-bars provide added margins of safety versus the LS series plastic lifter trays. And the shorter travel lifter acts like a solid roller at higher RPMs, but does require precise preload across all valves. It’s time consuming and painstaking to measure all 16 valves for very small differences in preload, but the additional valve control afforded is fantastic. The control comes from taking the slack out of the system and allowing the cam lobe to transmit valve action without losing much transmission of force. To aid in this, I always recommend the stoutest pushrods that will fit. Even with regular, stock-type lifters, pushrod flex is a bad thing.

The bigger, stiffer pushrod deflects much less. When a pushrod deflects, it acts as a secondary spring, absorbing some of the lift action from the cam before it is transmitted to the valve and can actually try to vault the lifter off the cam, allowing it to loft before everything crashes back down once the pushrod recoils back into place. This is one reason why folks have to keep adding more spring pressures with aggressive lobes to counteract the lifter loft from the pushrod deflection. The problem is your lifter has to be able to withstand that increase and most stock type lifters cannot. Either way, no lifter, cam, or pushrod will take that abuse for very long. When you have 400+lbs of open pressure smashing metal parts together, repeatedly, things begin to wear and fail. Once the hardening on the lifter axle or cam lobe begins to scrub off, the cam or lifter will fail eventually.

Finally, you want the rocker to be strong in the right area: around the pushrod cup. This is where the pushrod sits, between the lifter and the rocker. Added material here does not affect MOI as much as over-the-nose weight, but it does add weight and thereby affect it to some degree. As with anything, there are trade-offs and the rocker still must be engineered correctly, but weight here is preferable to over the valve. If anything, weight on this side of the rocker, produces more strength and reliability in the entire valvetrain system. So be sure to check your rocker choice for added material in this area.

Cam Lobes and Conclusion

The cam should have a fairly mild lobe, designed for endurance, RPMs, and longevity. That way, you’re able to build the valvetrain system as light as feasible, reducing the spring pressures and decreasing the friction and weight of the valvetrain. And valvetrain stability is the key to both power and reliability. Go with only as much spring as you need and nothing more. Look long and hard at beehive springs, the biggest pushrods you can fit, lightweight and strong rocker arms, and lifters that can take the abuse.

And combined with an endurance type lobe, you aren’t giving up much if any power due to the better valvetrain harmonics. Let the heads and the intake/exhaust do the work of making the motor an efficient airpump. Don’t overcam or put the nastiest lobes in there. You won’t see a faster car, but you’ll see one with more reliability issues.

It's funny that you posted this today. I bought Comp's new conical design springs and I was just measuring the weight of my new springs against some other popular springs out there to compare.

Conical Springs w/ stock steel retainer and locks = 73 grams
Beehive Springs w/ stock steel retainers and locks = 93 grams
Dual Springs w/ titanium retainers and stock steel locks = 107 grams

That's pretty big.

Imagine those with Ti retainers...

I was looking at picking up a set of these for my eventual motor build. Paired with HUC lobes, thick pushrods, and a stock rocker with a trunnion upgrade, I think I should be set up for a nice setup.

Awesome sticky and written in a way that everyone can grasp. Bravo sir

Thanks. It's the sum total of a lot of the things I've learned with valvetrain applications. I don't get into any specifics here, but the generalities just to help you as you build your motor. Ask questions and make sure the people you are buying parts from have a similar philosophy to what you want to do. Saving a few bucks or going with something on the shelf isn't always the best way to build an optimized valvetrain.

Good sticky man. This stuff is very critical in a pushrod engine. I don't think most understand it or there would never have been a dual spring put on a hydraulic cam ls1.

Great sticky!

Question, would I be better off going with a conical or beehive over the PAC .650 dual for a XE 224/228 .534 .537 lift. I will be using my SLP 1.85 rockers which will increase the lift to .58x/.58x, but I wondering if the PAC's are too much spring.

Good info. A lot of people buy into aluminum rockers as better but IMHO they are not. The MOI with the big steel roller and bearing at the end take away any overall weight advantage and there isn't even much of that. It's like people think a pound of aluminum is lighter than a pound of steel. I like the fatigue factor of steel vs aluminum too.

I'd do a beehive for the XE lobe. I don't know enough about the conicals for the LS1 yet, so it might be better to go with a tried-and-true beehive. PAC 1212 or 1218 would work.

That is my thinking also. The heads that I bought currently have PAC 1904's with Titanium retainers.

I'd stay duals as that 1.85 rocker ratio will magnify the jerk intensity of that lobe profile

I remember you mentioned that when we talked. I spoke with Tony Mamo and he also suggested sticking with duals. So that is what I will do. Thanks Jim!

Great write up Jake!

And its always a good thing when the jerk intensity gets magnified!! :D


(Sorry.....couldn't resist!)

Guys....its real simple....if you can control the valve perfectly with a dual why not do so.....you have a far greater margin of error from a broken spring. A single spring breaks and the chances of not lunching the entire engine is slim....with a dual spring it makes noise....has a miss at high RPM....doesn't pull with as much authority at high RPM....you have a alot of warning signs if your smart enough to take the time and listen. With a single spring breakage, its all over very quickly.

The single springs offer good control from their lightweight no doubt but once again, if the spring breaks its usually a complete meltdown if you drop a valve in the hole. At low RPM you may just mess up the heads real bad....possibly the piston is salvageable, but if it busts at a decent RPM your probably out a complete engine and may even crack the block. Its ugly with a capitol "U"

Also guys think about this entire scenario as weight versus rate....a light spring is great and has less mass but a slightly heavier dual may have more seat and open pressure which allows it to handle the additional inertia of its own mass. I was never so nervous as the month I drove my Vette around with a single beehive Comp spring waiting for the first shipment of AFR dual springs. The chances of failure is slim with a high quality single spring but the chances of total destruction is high with the same choice if your one of the unlucky ones.....you have to weigh the risk/reward and why take a risk if a properly chosen dual can offer you the same power and peace of mind as well.

Some may say factory engines run with single springs for hundreds of thousands of miles and that is true for the most part but there is NO comparison in the springs themselves (light load), cam design (super soft profiles), and RPM.....its apples and oranges when comparing what we generally run to what the OEM's do.

Beehive/Conical spring technology is awesome....I see its appeal.....but I also see the inherent risks involved. You guys have seen the packages and complete builds I have designed and shared the power curves with....to 7000 RPM or more you might think it was a solid roller set-up based on the perfect arced curve that clearly shows excellent valve control.....every one of these have been achieved with the right combination of a dual spring, the right pushrod, and a quality rocker arm (usually a Yella Terra Ultralite) with the right geometry achieved thru shimming the height of the stands properly.

Lots of ways to skin a cat....personally Im alot more comfortable skinning it with a lightweight dual valvespring

Hope this helps...

-Tony

Quit "jerking" these guys around Tony, we all know a beehive is the "bee's knees"!!!

Couldn't help it myself either!!!

LOL

Your right Martin....my philosophy is entirely too logical.....LOL

I like the technology....I get it....I understand why and how it works but if you could have the exact same smooth power curve with a much higher level of reliability why wouldn't you??

Im also one of the few guys to have back to back tested the older gold standard of Beehives (918 Comp) on the dyno versus our lightweight duals. The curve was a layover till 6700....and smoother and higher with the duals till 7K when we terminated the test. It was obvious the valve control at the very high RPM's liked the additional seat pressure and spring rate the duals offered.

This is another topic that will always be hotly debated and the answer is no one is right.....know the upsides and downsides and risks associated with your decision is all Im preaching. I respect everyone's opinion but feel strongly enough about mine to take the time to share....(and right now my life is total chaos so time is a luxury Im short on!).

I cant think of a good bees knees come back.....LOL

If a single spring breaks the financial crippling of that event will bring you to your knees.....there we go! :judge:

Catch you guys later!

-Tony

OK guys....you cant make this stuff up

I just hang up with a guy in New Zealand inquiring about some Mamofied 230's for his new LS2 based stroker engine. Half way into this conversation he mentions the reason we are even talking is his engine builder talked him into beehives and one of them failed leaving the intake manifold as the only functional component he has left. I am not making this up and actually asked him to post in this thread as one of the "unluckys". Turns out he isn't on this board (blasphemy!) but the timing of this call was uncanny.

There is alot of GREAT info in this thread and Jake's presentation was top notch. Martin, nothing but respect and I hope you realize I am just having some fun while also trying to make a point. Sometimes there is no "tonality" in posts and things can come across harsher than intended at best.....completely mis-understood at worst.

Lightweight springs are awesome....I agree completely and I understand the why's and how they work as I previously stated. In fact I'm a fan of most engine components that can be made lighter and still live. I just wanted some folks to understand they do come with a very low percent (but high degree) of risk because anything can break....I don't care who's name is on the box. A spring is a stressed metal and metal can fatigue and break sometimes sooner than intended.

Didn't mean to derail this thread or take anything away from it....I just have enough background and experience with all of this that I felt my opinion (although somewhat against the grain?) was worth a listen.

-Tony

For what it's worth, I run duals. I also run a double-roller timing set.

But on very low intensity lobes, I think beehives have their place. Even the EPS lobes I run, which are fairly mild, really need duals.

https://ls1tech.com/forums/advanced-engineering-tech/394940-those-who-want-big-nasty-cams-lots-lift-etc.html

My how times have changed. That thread made me think Beehives were the "Bee's Knees" and when I saw Predator-Z used PSI 1511ML springs on a cam with 238 XFI intake and 236 XE-R exhaust, I wanted them too.
Reading this, his engine should have never survived a dyno tune.

Bee Healthy, Eat Your Honey (and buy duals) ?

How can both threads be right ? Something is not adding up for me here.