Does Isky still sell hardfaced overlayed solid lifter cams that I think use "chilled" cast-iron lifters?? I want to say that this combination together make parts "hard as the hubs that hold up the gate to hell"!! pdq67
Lengthening the pushrod only changes the starting point of the "event" at the rocker arm... There are only 3 ways to increase the valve lift (and one only REALLY works with solid lifters). First is to grind the cam with more lift, either with more material to start (new blank) or by reducing the base circle.. Second is by increasing the ratio of the rocker arm IE; from 1.5 to 1.6 Third is by reducing the valve lash ( solid lifter only ) IE; reducing a .030 lash to .022 gains you .008 more lift... Dave
As the cam rotates, the lobes move the lifters a defined distance in a straight line. On an OHV engine this happens quite a distance away from the valves that are being opened and closed. As a result, some kind of linkage is need to transfer this lifter motion from down inside the middle of the block to the top of the cylinder heads. And on this style of engine it also has to change the direction of this linear motion. A center pivoting rocker arm is the simplest way to make this change of direction with one end of the rocker contacting the valve stem. But the other end of the rocker arm is still quite a distance from the lifter. To make a mechanical connection between the lifter and rocker arm, the pushrod is installed to fill this maybe 6" or so gap. At it's most basic level, the pushrod is only there to take up space. It can't do anything to increase or decrease the amount of lift ground into the cam lobe. And short of deflecting or bending or pushing it's way thru the end of the rocker arm, it can't change valve lift. When everything is working as it should, the most it can do is transfer motion with no mechanical advantage. Think of it in terms of a kid pulling his Radio Flyer wagon down the street. The kid is the "cam lobe" providing linear motion. The wagon is the "valve" he has to move. And the 3' long handle connecting the two is the "pushrod". If the kid walks 10' the wagon will also move 10' behind him. Now put a 6' long handle on the wagon and have him walk another 10'. The wagon will be further behind him, but it's still only moved 10' from where it started. There are reasons to install shorter or longer pushrods in an engine but for the most part this is determined by cam specifications, machine work done to the deck surface of the block or heads or the usage of aftermarket rocker arms. The changes are mostly to correct valve train geometry to prevent binding in the rocker arms and to properly position the contact area of the rocker arm tip on the valve stem. Here's a link that explains the procedure. Generally, it's not even an issue on a stock or even slightly warmed over street engine. http://www.peteandersonracing.com/Tech.html
Great thread, a real thinker if there ever was.This question is for everyone on there first break in of a new cam/lifters set. Did you feel uncomfortable with that new engine runnimg 2500 rpm with no load ?? ........Me first,383 Dodge, i rebult the motor my first v8 was used to the vw flat 4(with nare a problem).I read the directions ,and when i fired it off i was so proud($broke)but proud then 2500 rpm ,i was sweating big time scared to death something was going to happen,it sounded almost wide open to me.To be honest i think i lasted 8 min ,i know it wasnt 10. When i do my 413 im going to get it going and leave a friend with it and leave the area. haha i will most likly realy do that.I have faith in my work on diesel or gas but something about no load just bothers me,a part break $$$$ ect.Ive got a gen i use at times and i hate the way it runs almost wide open,,Do i need a shrink ? dont answer that haha.Any body bothered by it? .....................................YG Or as a quote on hamb build a bridge and get over it?
O.K.-Finally got it HOWEVER-It is an arguable point that If there is zero lash that there would /could be a few thousands difference due to push rod length differences-but negligable. It would just wreck the valve train geometry. Thanks for opening my eyes Oldmics
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