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Does anyone know the effect of light weight valves in a flat head motor? i'm considering stepping mine up with some 5/16 or 11/32 stem valves to save a little weight in conjunction with titanium retainers I just don't want to throw the money into it if it wouldn't help things out. I'm looking on one hand gravity will help them close and possibly help with valve float and on the other the lighter valve train will let the spring work more effectively. Any input would be great!

My take on this, and your other posts, is that first lets go back and look at the basics of the engine you want to play with. It has a looong stroke so is not too conducive to running at higher RPM's. Because of the long stroke design, is the oil pump and system up to it if the RPM's are increased significantly? It was designed to run at lower RPM's than modern short stroke engines and generates it's torque and power accordingly. You're looking to re-grind the cam for more power, faster acceleration, higher RPM, etc. Breathing, whether by std or light weight valves, will be comprised by the size of the valves(overall head diameter) you can use. But, even after saying that, a good port and polish job will pick up a more than reasonable amount of "free" horsepower for you. Saying all that, my conclusion is that using lightweight valves and titanium components is probably not warranted. Why? Because by the time the RPM's of the engine reach a point where they'd be of benefit you've probably thrown a rod!

That's very good information and it also crossed my mind that even with light pistons and a hotter cam and all the related equipment to attempt to increase the RPM potential with a super long stroke would i be able to turn more than 5500 RPMs and have it survive.

I agree with Mr O.

There are cheaper ways to make big noise. For one thing those old motor parts have endured decades of periodic vibration and stress. Remember the old addage that expensive jet aircraft should be able to fly forever given proper maintenance? Well that theory broke up in the sky along with the Dehavellin Comet.

The opposite side of the spectrum is the Honda 1600 DelSol - arguably the most advanced combustion chamber in the world. You can bolt on turbos and what not and the thing will blow itself up from hundreds of horsepower. But try to change the internals for more performance? Forget about it.

There is a reciprocating limit for motors and the maximum performance is usually achieved via slightly under square. The flathead Packard is very undersquare and so theortical rpms are limited.

Titanium valves and retainers would be the last, least cost-effective dollars one could ever spend on a Packard I8.

jack vines