Measuring Push Rod Length

[Maverick]

I learned there are two ways to establish the correct push rod length.

http://www.carcraft.com/techarticles/11 ... ewall.html

Here the length is established with an adjustable push rod and a felt tip pen. Other sources say the length should be confirmed by turning the engine with the selected push rods installed and re-checking the witness mark on the valve stem. That requires either a checking (light) valve spring so the lifter isn't compressed or a solid lifter. None of the references I've found take pre-load into account.

Carl, of CarsByCarl.com, uses a very light checking spring and rotates the rocker by hand to make the witness mark. No solid lifter or adjustable push rod required. BUT, it does required removing two valve springs (assuming both intake and exhaust are checked), installing checking springs, and reinstalling the correct springs.

I'm going to use the first method because I already bought the extra lifter (dissembled it and with #10 washers turned it into a solid lifter), the adjustable push rod and some 24" calipers for $10 from Harbor Freight to measure the almost 9" push rod. And, I don't have a tool for removing valves with the head installed or the checking springs. Even if I had the stuff to do it, I'd rather not swap springs with the heads on.

When I disassembled the extra lifter to make it solid, I was surprised at how much travel the hydraulic lifter has. I'm no longer going to be worried about an extra 1/4 turn when setting preload. Doug, at Boyette's Machine Shop suggested a full turn, rather than 3/4 turn, on the Windsor in the F100. He thought that might quiet the lifters. Since he assured me there was no problem the way it is, I didn't readjust them. I've heard recommendations to do only 1/4 or 1/2 turn preload but don't see the point in that given the huge amount of travel.

[Maverick]

Here's another take on push rod measurement. This one doesn't check witness marks on the valve stem and doesn't use a solid lifter. https://www.youtube.com/watch?v=o5is9Bs ... load_owner

[Maverick]

Here's another utube video, this one by Summit. https://www.youtube.com/watch?v=OmzbHgVY3cI

I like this one because it doesn't require swapping the valve springs to weak springs. If there's oil in the crank case it also doesn't require a solid lifter. But, since I already made a solid lifter, I'll use it.

[TireSmoker]

I was about to post the link you used in your 2nd post. That one was mentioned up on chevelles.com, as it was just made a few days ago by a couple of the pro builders there. I liked it.

-Dave

[Maverick]

This video [youtube]http://www.youtube.com/watch?v=i_NpzU4pGjc[/youtube] was posted on 460ford.com. It shows how the valve spring and even the valve stem moves around at 7K RPM. I think it demonstrates why the roller tip needs to stay near the center of the valve stem.