It's been said and proven that weight over the valve seems to be much much more important in the valve train then weight over the lifter. This makes perfect sense in the world of a solid lifter obviously as a solid lifter cannot compress, unless a catastrophe happens ofcourse. Now, does the same hold true for a hydraulic lifter with a pushrod cup which obviously does compress. My concern is pushrod deflection which is a very real phenomonon according to many and obvious from the use of big pushrods in nascar, pro stock, etc. I'm going to be running 7/16" pushords in my setup to avoid the deflection caused by smaller pushrods, or atleast avoid most of it. Now that being said i'm looking into a hydraulic setup for a friend/customer and like the idea of 3/8" pushrods. Obviously we won't be running killer spring pressure on his hydraulic setup like my solid setup but will still be in the .61X" and up category with around 150ish 400ish open pressure with some good morel hydraulic lifters. Do you guys think that the morel lifters will be able to handle the weight of the 3/8" pushrod over the standard 5/16" pushrod with solid stainless valves, stock rockers, and a 6900-7000 rpm engine speed limit?

Any thoughts or practical examples are appreciated

 

A lot is going to depend on what kind of spring load and spring design you need to control the valve. Rpm in excess of what you propose is being done with Morels. I've seen some of the engines, but I'm not the builder.

I think you are on the right track with stiff pushrods, but not overkill. Pushrod deflection can screw up valve control, or it can be used to loft the valve in a somewhat controlled manner, but not on the hydraulic engine you are building.

Yeah, stiff is better.

 

Thanks man. I think all systems point to 3/8" pushrods, just seeing what you guys thought.

 

Ask you cam/valvetrain designer. That's where I'd go for the specifics.

 

Yeah, I figured it be best to consult with ETP (heads he'll be using) on spring choice, morel for the lifters limitations, and comp for the lobes and what they think will result.

 

I think this is mostly because of the effect of rocker ratio. Things on the valve side are moving .6 of an inch, and on the lifter side only .35 of an inch.

 

What about the mass on the lifter side which wants to continue in the upward direction as the lifter passes the nose?

Spring pressure is multiplied back to the lifter side according to rocker ratio,
but how much consideration should be taken?

Rev kits are certainly worth a few HP as the spins increase.

 

Lots

Yep, the pushrod sees valve spring load x rocker ratio even before you add the forces due to acceleration which can be considerable.

FWIW, head guys aren't necessarily cam design guys and a cam company tech may not recommend different lifters or pushrods from what he sells. Everthing in the valvetrain needs to works with all it's neigbors. A good cam/engine designer puts it all together with your specific vehicle requirements. That service can be free if you buy some or all of the parts from him, or he might charge a design fee if you want to buy your own parts.

 

Mass on the valve side wants to continue moving down too, at the same time the lifter wants to continues moving up. And that mass on the valve side has a greater velocity, because of the longer distance it has to cover in the same amount of time.

Good point on the spring pressure multiplication. Hadn't even thought about that...

 

Its not really rocker mass directly, but rotational mass moment of inertia that needs to be examined for the rocker. Valve mass is a direct acceleration as is the spring, retainer and lock mass. These have to accelerate much faster than the lifter/push rod, but the lifter/push rod are probably a good percentage of the overall system mass. I know you selected Morels, but I have always been curious as to whether there is a lifter that is lighter weight, and if so which and how much?

 

Morel hyd in marine applications with heavy valvetrain are seeing 3/8" and 7/16" pushrods in lengths as long as 9.650", with 170# on the seat and 500# open pressure with consistant rpm in the 5500 range for periods of 30 minutes or more.

Mass of the rocker on either side of the fulcrum is critical. Reduction of this will help stability in the valvetrain in the higher rpm ranges.

 

Thanks man, I guess that i'm ok if that is the case, ha ha.

 

Column Theory

Because a pushrod is an eccentrically loaded column due to angularity load and arc motion within the engines atmosphere, whenever possible, it is most proper to use either a single taper or offset dual taper design pushrod. It is also very important to use the largest diameter pushrod that you can fit in the engine. This will help lessen deflection in the pushrod by putting the major diameter and mass where it is needed the most. The greater the angularity, the greater the arc motion. As the pushrod encounters this, the high load area on the tube moves closer to the energy source. The energy source being the lifter, as it travels up the ramp of the camshaft.

It makes it even more important to use these tapered designs when using large roller bearing diameters, increased valve lash, very high engine speeds, high rocker ratios, rapid valvetrain acceleration and high spring pressure. These tapered designs make it easier for the pushrod to do its job properly, and will enhance the performance of all the other valve train components, which will enable the engine to produce the maximum possible horsepower. The tapered designs and large diameters will also reduce valvetrain harmonics. Do not be over concerned about pushrod weight.

The difference between a stock 5/16 diameter pushrod in a small block Chevrolet and a 7/16 to 3/8 tapered pushrod, represents a difference of approximately 2.5% of effective weight. This is because the pushrod is on the slow moving side of the valvetrain. The effective increase in weight between the two pushrods may be small but provides a huge increase in valve train stability. Remember the valve side of this valvetrain is the critical side where any weight savings will make marked improvements. No matter what we change, valvetrain stability is the goal.

Important Special Instructions & Suggestions

It is very important to determine proper pushrod length. Improper pushrod length can cause a number of problems including excessive valve guide wear, lessened valve lift, valve stem side thrust, coil bind, improper valve to piston clearance and also rockerarm to retainer interference (in some cases lash caps can be used to help correct rockerarm to retainer clearance problems).

Check the radius of the lifter receiver cup and rockerarm cup/ball before ordering to help prevent mistakes. Improper ordering may result in parts failure. Watch for variations from stock radius in aftermarket lifters.

Make sure significant oil volume reaches the rockerarm end of the pushrod to help prevent galling due to excessive heat generation and lack of lubrication. To prevent interrupted oil flow to the pushrod, it is very common and almost always necessary to modify the lifter body so oil flows through it no matter where it’s positioned in the lifter bore (call for details). Oil restriction in the engine block is not normally recommended.

When possible, try to use larger diameter pushrods to spread out the load and lower the stress on the tube. This will help lessen pushrod deflection. Heavy wall tubing is a good idea also, to minimize compression. Many problems occur when a pushrod is inadequate for the application.

In high RPM applications tapered pushrods are a must for the serious racers. Tapered designs help to dampen harmonics in the valve train; extended valve spring life and increased usable RPM will usually be noticed.

Do not allow over clearancing for the pushrod. This may cause the pushrod to move around or deflect more than needed. Clearance of .010 at the closest point, wherever that may be during its complete cycle is sufficient. The cylinder head and engine block can often be utilized like a big guide plate and dampening device, which stabilizes the pushrod. Just make sure that there is no interference problems when turning the engine over on the engine stand.

Tapered pushrods should not be used in guide plate applications. Improper clearance and interference problems are sure to occur. Use only straight tube pushrods, specifically surface hardened for guide plate use in this application. Note: See series #2 and #4 for guide plate applications.

If you are using a tool steel rockerarm adjusting screw, it is almost always suggested that a tool steel pushrod tip be used at the rockerarm end. This will ensure proper compatibility.

per Terry Manton - Manton Racing Products

 

Now that's some good damn info, thanks a bunch Ed!!!

 

You're welcome...

 

I don't know if the Morel lifter is a limited travel lifter, but if you want to run the RPM you indicated you should address that. I have run stock lifters to 7400 and every once in a while we would put a pushrod through the rocker. After limiting the travel that has all gone away. Never saw the need for the high buck lifters.

Old S Stroker mentioned lofting the valve with the releasing of the bending forces in the pushrod. That is kind if what we do in Stock and control the landing so the parts live. We have broken a bunch!

Rich

 

What do you mean by limited travel lifter? Altering preload?

 

That's what I'm thinking.

Those that are limited to stock lifter types are known to trick out the seats,
and run minimal pre-load for best power.

A friend of a friend...of a friend says that their CASCAR motors (not NASCAR)
run 0.001-0.003" pre-load and lock the seats to act similar to solid lifters.

 

You want to limit the plunger travel to like say .015 or .020. Preload the lifter about .010 and you will have a nice high reving factory lifter. Never had a lifter break. We make about 530 hp on factory parts and run very low 10's at 3200lbs. No need to trick out the pushrod seats.
Rich

 

So your saying to leave about .005" to .010" travel after setting preload? Is this travel limit mod done simply? TIA