Valvetrain weight vs. RPM limit

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street demon

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OK I know there is no clear cut answer on this but I would like some opinions. Lighter valvetrain equals higher max RPM without valve float so.....how much does it really matter? An example: A small block with some normal replacement stainless valves, locks and steel retainers against 5/16 stem stainless valves, lighter locks and some TI retainers. Both have 136 seat and 340 open pressure. How much RPM difference do you think there would be? Also both heads have the same rocker arms, pushrods and solid flat tappets. One last thing I've been running locks with recess for lash caps but don't run lash caps for 2 years now and I'm curious if I'm the only one. There is a small weight difference between the two and the cost was the same so I said what the heck.
 
The weight is not the key factor ,rolling resistance of the valve train is the key to higher RPM and getting to the RPM quicker.That is why a roller set up is far superior then a stock valve train for longevity and the speed it takes to get to your RPM limit
 
MADIRISHMAN said:
The weight is not the key factor ,rolling resistance of the valve train is the key to higher RPM and getting to the RPM quicker.That is why a roller set up is far superior then a stock valve train for longevity and the speed it takes to get to your RPM limit
Click to expand...

I agree, key is how fast it revs for better valvetrain components. You can bring it to a higher rpm without float, yes. But not every combo really needs to, or can make better power up there. But they will allow it to rev up faster.
 
I must have got some bad info then. I was always under the impression that the weight of the valve, locks and retainer was pretty much the limiting factor of RPM ceiling granted that had the right spring pressure. But you can only put so much pressure on a solid flat. I run jesel rockers by the way.
 
To me the cams ramps and spring pressures make more of a difference on valve float than the valve train weight.
The cams ramp speed will put tremmendous inertial force
on the components.
If you don't run lash caps, does the rocker ride off the center of the
valve stem?
Some good reading on valvetrains. This is a pdf file.

http://www.grapeaperacing.com/GrapeApeRacing/tech/valvetrain.pdf
 
The rocker tracks really good threw the sweep. I had to keep milling the heads to get it just right. Thanks for the link.
 
Force, inertia loads, and friction increase at the square of RPM so component weight will become a greater factor at higher RPM. Lighter is always better within the limits of strength (and budget). The Comp "beehive" springs allow a substantially smaller and lighter retainer for example. Roller rockers are sometimes (not always) lighter BUT they move their mass outward, over the valve tip somewhat diminishing gains. Roller tips are great for valve guide life however.

Lighter valvetrain components will allow an engine to rev a little quicker, but not nearly as dramatically as lighter pistons.

The advantage lighter components have power wise is they allow less spring pressure for a given RPM. Think about it, it takes horsepower to open those valves against stiff springs. Less spring pressure means more power to move the car. Less spring pressure means less friction at the lobe/lifter interface, and therefore less wear. Up to the point where you are limited by valve float, too little valvespring is generally better than too much.
 
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