Pushrod length questions

[Malicious]

Hi all,

Looking to order my push rods to suit the ducile iron adjusterble rockers.

Got a few questions as the length I need isn't as clear as I'd thought it would be.

I've spaced the shaft up with spacers that came with it. Made the geometry right.

Length cam up as 233mm 9.173" overall, cup is 4mm, so 229mm 9.016" actual, sound correct?

I'm looking at grabbing the comp cam 7442-16 - 9.03"

Gets complicated as when double checking, I found the checker I brought is actually 3/8" ball & cup even though it's advertised as 5/16".

The difference between the two is 1.637mm - half .8185mm. In theory, actually length would be 29.82mm 9.048". I measured to no threads showing, so the comp cams 7442 should still work, 1-2 threads out.

The Unknown here is how deep the push rod goes in the lifter. So I'm looking for some advice, I'm on a bit of a time line, so I'm not sure I'll be able to get a new checker in in time.

On a hydrolic lifter, how far in does the cup for the push rod sit?

Also, any other advice is welcome.

 

[miller]

On a hydrolic lifter, how far in does the cup for the push rod sit?

Seems to be the big mystery! Plenty of answers, many different, big range.

I've got to go back into my motor, starting over again on the same thing. Lucky not ready to fire it up yet. (Ordered pushrods for a Mopar, and got hollow tips. I knew better, but guess I was just glad to get the damn things!)

But, back to your question...have been researching, and come up with anything between .010, to the lifter 'cup' halfway through it's travel limits! LOL!
I'm not new at this, though most experience is just using stock parts and pieces. Bottom line is full time contact, not bottoming, not contacting the retaining snap ring. Most I've dealt with, the lifter cup was 'slightly' depressed, past the retaining ring. Yeah, I know, not much of an answer.

With the tappet (ha!) on the cam lobe base circle, for mine, going to shoot for .025.
Considering how the tappets work, filling with oil over and over, allowing the hydraulic angle of the thing to work, has never failed me. Just a little more critical on adjustable rockers, but with more to work with.

 

[Malicious]

Found my old lifters, looks like the difference is negotiable, I've factored in the height change based on the lifter and above thought process.

Here a pic miller, hope it helps you.

 

[miller]

Yup! The particular lifters used make up a big difference on the outcome. You should see the stock lifters I pulled from my 440 Magnum. Cup is deep, and seems there's no spring inside!
Special tappets? Don't know, but the ones I got have a cup more like in your photo...like the later tappets Ma started installing. That's why I couldn't use stock pushrods.
To put it plain...picking numbers is the same as picking parts and pieces! Hehe, pick your poison!
That 'pre-load' number is your call, even more so with adjustable iron rockers. Keep the cup off the clip, is the thought of the day...

 

[miller]

Thinking (dangerous!), but might help a little.

Personally, I'd wait until you have the correct sized checker...ball size.
Airplane stuff here, but still all parts and pieces. Both radial engine designs I re-built, used adjustable rockers, though each slightly different. This is more like Pratts, about the same style rockers, and adjusters.
On those, adjuster the rocker adjuster first! Simple, because like your's the adjuster must be in a certain 'range' to work right, such as oiling. On that type radial, after the rocker adjusters were all set (middle of the range), push rods were sized to each. On your's, things will pretty much fall into place, covering both banks, since sized parts are in line, just two banks.
On the Pratts, push rods were sized using internal spacers, kinda making a 'custom set' for each motor. Lol, but also working with a floating cam ring. A bit dif.

Main thing is the rocker adjusters sitting right, then getting the push rod length, giving the lifter pre-load you want.

 

[lewtot184]

use a ball and ball checking push rod, with 5/16" balls. place it between the tappet and adjuster ball (no threads showing on the adjuster) and lengthen the checking rod out until it touches the adjuster ball and lifter cup seat. measure the rod and add .060" for tappet pre-load. this will be the length (believe this is referred to as the theoretical length) you'll order. i don't recommend buying a shelf push rod set. call smith brothers in oregon, tell them what your working on, measurements, and they can walk you thru the whole process.