Measuring for new pushrods correctly

[thegreatjustino]

I am in the process of adding a new cam, aluminum heads, and roller rockers to my 351 F4TE block. I have watched so many youtube videos on measuring for the correct length pushrods, I'm pretty sure I have this correct but just wanted to ask here for peace of mind.

I measured these two different ways based on the videos I watched. One was by marking the valve tip with a dry erase marker and then adjusting my adjustable push rod to the point where the wear mark was centered on the valve when the lash was set correctly. The second way was getting the rocker to a 90 degree angle to the valve, calculating 1/2 of gross cam lift, and then tightening the rocker appropriately before once again using the adjustable push rod.

Both of these gave me push rod lengths within .05 of each other, so they came out remarkably similar.

My one concern is taking lifter pump up into account. None of the videos mention any difference between measuring the length on a dry engine vs. one that has had the lifters pumped up. My concern is with the lifters pumped up the pushrods will now be too long and possibly cause damage.

I have attached photos of my #1 cylinder with the engine at top dead center.

Any expert advice or comments here?

 

[Rustytruck]

Don't they do it with super light tempory valve springs so lifters don't compress?

 

[rmk57]

Or get a used lifter take the innards out, and make a solid lifter out of it.

 

[blubuckaroo]

I'm watching this thread closely, because I've gone through this. Mine worked out great, but did I really do it right?

I've been to never... ever pump up, soak, puddle, or float a lifter prior to assembly.
So, I went about the pushrod length measuring with a dry lifter.
Like I said, it all went well.

 

[EricLar80]

Mark the top of the valve with a sharpie, reassemble, and cycle the engine a few times to see where the mark ends up. The wear pattern on the mark will tell you if you are properly located. Centered at top dead centered will only tell you that one position.

I second the idea to make a solid lifter out of an old one; you can do this by taking one apart and putting a bunch of washers in it until you can't put anymore.

 

[Viperwolf1]

Depends on how you measured initially, if you dialed in the preload when making the measurements (works with an empty lifter because the lifter spring is weaker than the valve spring) or if you used a solid lifter (or a modified one) to prevent it from collapsing. Preload is easy to account for in the 2nd case. If you want 3/4 turn of preload on a 18 tpi fastener then the math is (3/4)/18=.042". Then subtract that from your measured length to get the true length when the lifter spring is loaded.

 

[yfz450sew]

I ordered a few solid lifters and did the dry erase marker method.