273 Style Rocker Arm Adjusting Screw

[340inabbody]

So as I started to adjust my valves I had a really hard time loosening the jam nut of the rocker arm adjuster screw.

What I have is a mix of both stock style jam screws and jam nuts (see middle picture). I had faced all rockers when I had them out btw.

The ball end rocker screw (see top pic) appears to jam a standard 3/8-24 nut while the nut used is also a jam nut. It explains why I had a hard time getting it apart.

Question is the correct set up for this type of assembly to use only one element (screw or nut) that has a locking or interference fit not both as I seem to have?

In other words the ball end 3/8x24 adjuster screw supposed to have some type of locking or interference fit towards the too? The threads are not damaged look ok. But a standard nut stops tight at the too end away from the ball. Something doesn’t make sense to me.

I am looking to change over to the hardware on the right with the 12 point see last picture. Would that be a standard thread on the ball end screw and a locking/interference nut?

Thanks

 

[4spdragtop]

Factory didn't have lock/jam nuts. They are what's called interference fit. I redid my rockers and ground a flat spot and used lock/jam nuts on the 340.
Previously when we redid the 273, we left the rockers all oem with interference fit.

 

[340inabbody]

Factory didn't have lock/jam nuts. They are what's called interference fit. I redid my rockers and ground a flat spot and used lock/jam nuts on the 340.
Previously when we redid the 273, we left the rockers all oem with interference fit.

Thanks I ground flats on mine a while back. What I would really like to know is when you have two threaded parts are both set up with interference threads like what I have? This doesn’t seem correct as they are way too tight when both engagements close. I would think either the nut would have the interference thread or the stud but not both like I have.

 

[4spdragtop]

I dont recall rethreading the screws, but the threads will "change" somewhat going thru a grade 8 nut.

Thanks I ground flats on mine a while back. What I would really like to know is when you have two threaded parts are both set up with interference threads like what I have? This doesn’t seem correct as they are way too tight when both engagements close. I would think either the nut would have the interference thread or the stud but not both like I have.

 

[Oldmanmopar]

I use Max wedge style threaded ball adjusters and nuts, They are 5/16 24 thread . I see one in your picture with a screw driver slot. big block cranes are 3/8 24. All cranes are allen head style. also used hardened jam nuts.

 

[Oldmanmopar]

If you are using used rockers on new or different valves check for wear. We resurface all of them when used.

 

[340inabbody]

I use Max wedge style threaded ball adjusters and nuts, They are 5/16 24 thread . I see one in your picture with a screw driver slot. big block cranes are 3/8 24. All cranes are allen head style. also used hardened jam nuts.

View attachment 1716311473

View attachment 1716311474

View attachment 1716311475

View attachment 1716311476

View attachment 1716311477

View attachment 1716311478

View attachment 1716311479

View attachment 1716311482

View attachment 1716311483

Thank you, so are the threads of the ball head screw you show from Crane a standard 5/16x24 with no interference? Just the nut that has the interference thread?

 

[Newbomb Turk]

So as I started to adjust my valves I had a really hard time loosening the jam nut of the rocker arm adjuster screw.

What I have is a mix of both stock style jam screws and jam nuts (see middle picture). I had faced all rockers when I had them out btw.

The ball end rocker screw (see top pic) appears to jam a standard 3/8-24 nut while the nut used is also a jam nut. It explains why I had a hard time getting it apart.

Question is the correct set up for this type of assembly to use only one element (screw or nut) that has a locking or interference fit not both as I seem to have?

In other words the ball end 3/8x24 adjuster screw supposed to have some type of locking or interference fit towards the too? The threads are not damaged look ok. But a standard nut stops tight at the too end away from the ball. Something doesn’t make sense to me.

I am looking to change over to the hardware on the right with the 12 point see last picture. Would that be a standard thread on the ball end screw and a locking/interference nut?

Thanks

View attachment 1716311406

View attachment 1716311407

View attachment 1716311408

Run a sharp tap through the rocker. Interference fit adjusters were used to reduce costs.

Don’t mix the two types of adjusters, meaning don’t use a straight threaded adjuster in an interference hole and the other way around.

 

[340inabbody]

Run a sharp tap through the rocker. Interference fit adjusters were used to reduce costs.

Don’t mix the two types of adjusters, meaning don’t use a straight threaded adjuster in an interference hole and the other way around.

I do have a mixed bag of adjusters this was bothering me for a long time. But when I went to remove one, they were jammed together so tight that I needed a torch to take them apart.
What do you recommend I use? I want to replace all of them so I know that they are compatible with each other.

 

[RustyRatRod]

Thank you, so are the threads of the ball head screw you show from Crane a standard 5/16x24 with no interference? Just the nut that has the interference thread?

No. None of the aftermarket replacement parts are interference fit. The only interference fit is from the hole in the factory rocker arm. When you replace the factory adjusters with aftermarket adjusters and lok nuts, you cut the interference fit out of the rockers with a tap the same size as the threads in the rocker so they will no longer be interference fit. That's the purpose of the lock nut. It locks the adjusters in place.

 

[4spdragtop]

If you plan to buy new, make sure you find some 1st. I had issues trying to locate new in the proper.thread size.