Originally Posted by Flyin 57 Chevy
Hey......Hoping someone has a clue to this question please: I am swapping a stroked 383 1996-2000 Vortec roller cam block into my 57 Chevy. I am going to be installing my existing Patriot Performance aluminum heads onto this block. The valves in these heads are .100" longer then stock. I will be running a Comp HYD. roller cam/lifters and my question is this: any idea what lenght push rods I need to be using? I know the proper answer to this question is to use a push rod length checker but I was hoping someone ran into this issue already. Thanks very much!
The only safe way is to get an adjustable check push rod and adjust it till the rocker has proper sweep on the valve stem. Then measure and order what you need.
Any other method involves too many assumptions that dimensions as stated are same/similar as exist in reality or that you've covered all the dimensional variabilities. The push rod length is subject to block deck height, head to rocker height which among other things is affected by milling, not just stem length compared to stock but how deep the valve sits on the seat, how deep the seat sets in the head, where the rocker stud is against where it should be, and certainly the rocker's type and dimensions. It is also subject to where the cam is in the block as that affects lifter height, and where the lifter is in 3D space as to position and angle.
The dimensions and machining tolerances of all this stuff come into play, so knowing by looking and measuring is a lot safer than taking info on data sheets as gospel.