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By Bobby O 55 - 12 Years Ago
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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.
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By NoShortcuts - 12 Years Ago
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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'. 
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By ejstith - 12 Years Ago
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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.
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By paul2748 - 12 Years Ago
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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.
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By Ted - 12 Years Ago
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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.
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By lyonroad - 12 Years Ago
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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.
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By DANIEL TINDER - 12 Years Ago
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Ted (12/20/2013)
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.
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.
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By aussiebill - 12 Years Ago
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DANIEL TINDER (12/20/2013)
Ted (12/20/2013)
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.
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.
Why not just follow Teds reccomendation? what was suggested 40 yrs ago was then and parts were avail, this works today.
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By The Horvaths - 12 Years Ago
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Interference-fit threads are deliberately cut over and/or undersized. See here: http://www.sportpilot.info/sp/Machinery/27_Thread_09B.pdf
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By DANIEL TINDER - 12 Years Ago
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aussiebill (12/20/2013)
DANIEL TINDER (12/20/2013)
Ted (12/20/2013)
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.
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. Why not just follow Teds reccomendation? what was suggested 40 yrs ago was then and parts were avail, this works today.
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?
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By Moz - 12 Years Ago
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to my mechanical brains way of thinking changing from the friction screws to the stud/jamb nuts would naturally require running a clean up tap through them to make sure all threads weren't damaged, and the studs don't bind & run through the threads easily.
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By DANIEL TINDER - 12 Years Ago
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I COULD see where smooth running threads might be advantageous when adjustment is done with a screwdriver instead of a long handled wrench.
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By Ted - 12 Years Ago
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DANIEL TINDER (12/21/2013)
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? Ford used two different thread designs for the rockers. Both are 20 tpi but the thread cut is different. The early adjusters (1954-1956) using the jam or locking nuts is a conventional 7/16 X 20 cut while the 1957 and newer rockers used a friction style of adjuster that required an interference thread design to keep the adjuster tight without the use of a jam nut. To use an early adjuster stud and jam nut combination in the later model rocker, simply re-tap the threaded hole with a conventional 7/16 X 20 tap to clear out the interference threads. It may be necessary to machine a flat on the top of the later model rocker so that the jam nut will tighten squarely on the rocker. I suspect that a TSB regarding this would have gone into more detail than to say to simply replace the adjusters from one style to another.
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By DANIEL TINDER - 12 Years Ago
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Good info Ted. Don't recall reading service letter in question, only it's mention. Not unexpectedly, it wasn't included in the club compilation of T-Bird related letters, as it obviously took quite some time for enough clearance adjustments to wear out the threads. Nonetheless, though I have kept up with all the available Y-Block literature & internet chat these last 15 years, surprisingly, this is the first mention of the thread incompatibility problem I have yet encountered. Strange, with the mixed grab bag of rocker ratios & adjuster types found in service over the years.
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By bigmerc55 - 11 Years Ago
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I'm trying to do the opposite with my rocker arm adjusting screws. I'm trying to switch the self-locking adjuster screws from 143.1 rockers to my new 154.1 rocker arms that have the old type screw adjusters with jam nuts. The ball on the adjusting screws on my brand new rocker arms wore out in 100 miles because they apparently weren't hardened metal. The self locking adjuster will go down a couple of threads in my new rocker arms and then locks up so tight that you can't turn the ratchet with a cheater bar. I ran a 7/16 NF-20 tap through the rocker arm and it turns through with no resistance. The 143.1 rocker arms were rebuilt and had new self locking adjusters. Is it possible I have an oversized 7/16 - 20 self locking adjusters?
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By Hoosier Hurricane - 11 Years Ago
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Ford furnished .002 oversize friction adjusting screws to be used when the standard screws did not stay put. The original standard screws had a 1/2" hex for the wrench, the oversize screws had 7/16" hex. A bit aggravating when you find an engine with some oversize screws and some standard, causing you to keep switching wrenches as you go through the valves. The same screws were also used in the solid lifter FE engines.
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By bigmerc55 - 11 Years Ago
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Thanks John, I suspected it had to be something like an oversized adjuster screw and mine does have the 7/16 head on the adjuster. So I would assume that if I buy a new set of adjusters like the one's in Mac's Antique Auto Parts they should be the original standard size....I hope!
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By 2721955meteor - 11 Years Ago
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had a couple of loose selflocking, backed them off cleaned with starting fluid, aplyed some lock tight and adjusted left the engine over night.that was 3 months ago and checked the other day they have not moved.
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