I started my build with a stock rotating assembly and 58cc cylinder heads. At that time I had 7.5 length pushrods with perfectly centered rocker rollers on tips of valve stems. I have since upgraded to a stroker rotating assembly and had to go with a thicker .041 to .091 head gasket to bring the compression ratio down to 10.5:1. I wondered if I need longer push rods so I have done the test. From the pictures I can tell they are a little short but is it enough to cause problems? I am not sure. What do you think?

 

Where the roller runs on the end of the valve stem tells you nothing about the valve train geometry. It really makes no difference as long as it isn't running off of the edge. What you want to look at is the motion created by the rocker arm as it goes through the lift cycle. With most rocker arms you want to see the roller move outward, stop and then sweep back inward toward max lift. If it approximately splits this difference it's were you want to be. In other words it could possibly be better now than before.

 

Very good information. I will cycles the engine and look real close at the sweep.

thank you!

 

Everybody has different ideas when it comes to valvetrain "geometry". If you subscribe to Jim Miller's Mid Lift Geometry theory about the best you can do when using a rocker arm that isn't designed that way is to make it split the difference in movement. What's interesting about the tip movement is how some designs approach it differently. One time I sent a note to Jesel and asked them what their set up tool tries to accomplish and what is their goal when it comes to geometry. Someone called me and we talked about it where I was told that they try to make the rocker arm produce the most movement early in the lift cycle and the least toward max lift. The reason is so that the most movement happens when the spring load is the lowest. Maybe that makes sense and can be done easily with a stud mount setup by making the pushrod shorter.

With that thought in mind it is probably always better to have the a little too short than a little too long. It tends to make the rocker ratio higher/give more lift too but this effect is extremely small.

 

You have moved your head .050 away from block using thicker gasket.
My cam recommend to have 0.045" of preload after zero lash.

I you had .045 of preload before, you may have 0.005" gap where lifter and valve are not touching, and not be set at zero lash, your lifters will be too loose.

Roller tip sweep pattern has nothing to do with length of pushrods. You can have a great sweep pattern with short push rods, engine will sound like a bunch of clams, and your valves won't be opening to the lift advertised on cam.

After bolting on the head, you need to check push rod length, and have correct pre-load set on your rockers/pushrods/lifters as advertised by the cam/lifter manufacturer.

If everything as 'perfect' before, meaning you had the correct length pushrod to begin with, then in theory, you need to get .050 longer, or 7.55" pushrod length.
Again, that is a theoretical value, you still need to set preload, measure, and verify length. If your sweep pattern is not correct, then you need to add/remove shims as required.

I'd invest in an adjustable push rod length tool, and checker valve springs(or whatever there called), then you can do all and get or verify you have the correct push rods.

 

There are so many things wrong with this post it's tough to figure out where to start. While it is true that you would lose preload that would only happen with a non adjustable valvetrain which this isn't.

Roller rocker arm sweep has just about everything to do with pushrod length. Why? Because in a stud mount valvetrain the height of the pushrod tip along with the valve stem tip and stud determine the locations of the pivot point and thus the amount of sweep seen on the valve stem tips.

A shorter pushrod will lower the short end of the rocker arm and the pivot point on the stud relative to the the end of the valve. This can GREATLY alter the sweep seen on the valve stem. AND it will cause the rocker arm to reach 90* to the valve stem later in the cycle. This means that the rocker arm ratio is HIGHER with a shorter pushrod and you'll have MORE lift not less. The only reason that the engine would be noisier is because you've introduced some sort of interference usually between the pushrod and the head.

These effects are pretty small and the changes are surprising small even when the length is radically changed from way too long to way too short. It just doesn't change the overall lift as much as it seems like it would with a cam having say .565 lift with a 1.6 rocker.

 

Sorry, I had assumed this was non-adjustable rockers.

With adjustable rockers, I think you will be fine with your pushrods. Like what @DaveMcLain said above.

 

I can understand why you'd think that he had the non adjustable/bolt down style rockers since that's what most Ford engines had originally. I've done aftermarket hydraulic rollers in 460's and 400's using the stock rocker arms by just playing around with the pushrod length till I ended up with .060 or so preload in the lifter. They worked just fine. All of those were under .600 theoretical valve lift but I do wonder for what lift the stock pedestal height is really optimized.. I bet it's probably ok for .500 lift but probably it should be cut down some for .600. I don't know.