Longer push rods ?

[Reed Granrt]

Originally Posted by Bill Bogues

Danny, In our stocker 350's every time I"ve went from a stock pushrod to .100 long I always picked up .007 to /008 lift. With a long pushrod i would also check the rocker arm contact point on the tip of the valve and make sure it"s not running too close to the outside of the valve tip. Ideally you would want the contact point of the rocker arm to be centered on the middle of the valve tip at mid lift. Hope this helps.

Bill
I hope you do not mind me adding to your input and I will apologize if I miss speak. You are indeed correct in that ideally you want the contact point in the middle of the valve, BUT that has nothing to do with proper rocker arm geometry. The camshaft creates circular motion that transfers that circular motion to a push rod that is moving vertical. It then converts back to circular motion thru the rocker arm which in tern converts back to vertical motion by pushing down on the valve. Proper rocker arm geometry will give you the shortest scrub pattern across the valve. And as a result of this shortest scrub pastern, the engine and valve train uses the least amount of force to push down the valve. I have seen people miss the geometry so bad that it took 20 ft.lbs more force to rotate the engine thru a revolution. WHERE the rocker pushes down on the valve doesnt matter as long as the scrub pattern of the rocker doesnt go off the valve or damage the valve tip. It must stay in full contact of the tip. Where it pushes down on a valve does not wear the guide any more than to be in the center. Remember you are converting circular motion to a straight line motion. But the length of the rocker scrub will wear the valve guide and or valve and generate more friction than is needed. The length of the scrub pattern is the result of geometry, so my opinion is to get it correct when possible.
Dagone it Bill, I sound like a know it all. I hope I learn sumtin every day and to day is early so even at 64 I gots plenty of time to learn a lot today. You can duplicate this and you will be surprised at the forces that can be generated in the valve area. You can be surprised at the forces you can take off the cam, rocker arm, and pushrod