Pushrod length

[Tony 69]

So thinking about pushrod length, other than where the rocker meets the valve tip. The cam controls the amount of lift. If I have no lash is the length important? Does it depend on solid or hydraulic lifters? I think yes but buddy says no. What do you all think?

 

[BLK 68 R/T]

Hyd. vs solid does matter on length. Best thing to do is to measure for what you need.

 

[Lefty71]

If I have no lash is the length important?

Do you mean because they are for hydraulic cam?? If you are altering anything and staying very close to the factory set-up, then use the factory length....no brainer. If significant changes are made with cam, aftermarket heads (shaved heads or decked block), change of rocker style, then yes, you would want to verify the rocker geometry, pushrod length needs to be set-up and interference to tunnel (head) checked as well.

 

[Tony 69]

Yes I do have aluminum heads. My thought was the geometry where the rocker pivots. A shorter pushrod will not open the valve all the way even if it’s adjusted properly. ?

 

[Lefty71]

A shorter pushrod will not open the valve all the way even if it’s adjusted properly. ?

No....it will work. Within reason. The main reason you are going to want to hit the length right on is to be easier on the rocker and the adjusters. Pushrods that are too short will cause undo stress on the adjusters and the rocker tip as well as making for unnecessary long motion, which is very bad at high RPM's. And of course, too long just wont work.

 

[HawkRod]

Remember that a rocker arm pushes in a circle. Think of the rocker tip, shaft mounting location and pushrod connection points as a line. This line moves in a circle. The pushrod merely moves up and down. So the maximum movement from a pushrod to the rocker is when this line is at a right angle to the pushrod. If the pushrod is at a steep angle, part of the travel of the pushrod is moving sideways.

Bottom line is you will always lose some of your cam lift due to the rocker arm geometry. For example, if you have 1.5 rocker arms you will not get 1.5 of the cam lift. A proper length pushrod will minimize losses due to the rockers.

Will you notice it if it is not ideal? Probably not.