I have a 1955 Fairlane with a 272 cu in. Should the rocker arms have a screw and lock nut for adjustment or just the other type. When I bought the car it had the other type. I guess you can use either one. I adjust the valve lash while the motor is running. Much easier with the other type of adjustment screw.

My recollection is that the screw with lock nut system was original y-block FoMoCo equipment for model years 1954 through 1956. For the 1957 model year, the 'self locking' or interference fit type adjusting screw was substituted by the factory. As you indicated, the '57 through '64 self locking style are easier to use and less time consuming to set.

I THINK I recall reading in a Ford service letter or the '57 Ford repair manual that if the self locking adjusters would not hold their adjustment, the earlier style screw with locking nut should be substituted.

Things 'evolve'.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

I had a 57 312 that had the lock nuts. I didn't even know they made self locking until I got my 56. On one side I had different sized lock screws than the other side. I had some that wouldn't hold so I got some lock nut ones from Tim. They are a little of a pain to adjust but once set they don't loosen up.

Doing Fords for 45 years. '56 Customline Victoria

E.J. in Havana FL

Theoretically they are inter-changeable. I have a 57 set (originally interference) and I replaced one with the nut type. Very little room for adjustment. It seems that the interference type has a thicker boss. It did work though. I only changed one because of this.

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

If converting the friction style of rocker arms adjustment screws over to the earlier stud and jam nut combination, then a 7/16 X 20 tap needs to be run through the rocker arm threaded holes to restore the thread finish to one that’s suitable for the earlier stud style.

Lorena, Texas (South of Waco)

Ted, I've recently wondered about this but have only heard it once before. There have been posts here before about switching from the friction type to to the locknut style. When I took 2 dozen rockers in for resurfacing I suggested this to the machinist. He said yeah but the threads are slightly different on the two types. In my case they were able to find 16 rockers that had tight threads. They actually had an old box (the brand escapes me - it wasn't one of the well known makes) of oversize adjusters with the correct size tip but they weren't needed.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia

Ted,
Please elaborate. I was under the impression there was a Ford service letter advising those who's friction adjusters were worn from frequent adjustment to replace with the old jamb nut style. If there was originally any difference in the rocker threads, why would they recommend swapping adjusters as opposed to merely running a tap through the rocker, adding a jam nut to the friction screw, or purchasing oversized adjusters? BTW: Will running a cleanup tap improve adjuster screw friction? If so, then why were oversized adjusters made available? More to the point: What is the specific problem encountered when merely swapping adjuster types (that requires the cleanup tap)? Confusing subject.

6 VOLTS/POS. GRD. NW INDIANA

Why not just follow Teds reccomendation? what was suggested 40 yrs ago was then and parts were avail, this works today.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Interference-fit threads are deliberately cut over and/or undersized. See here: http://www.sportpilot.info/sp/Machinery/27_Thread_09B.pdf

Largely because I don't currently have a problem (aftermarket rockers/friction adjuster screws with jamb nuts). Just cursed with curiosity/inquiring nature, though I do understand that others don't require explanations, and are merely content to follow instructions.
P.S. I should assume then, that the rockers equipped with friction adjusters had interference female threads, but the earlier models did not? Still not clear about why the old style screws would not function properly unless a cleanup tap is used?

6 VOLTS/POS. GRD. NW INDIANA