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By Half-dude - 10 Years Ago
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Hey guys, real quick question here.
My 272 is clicking like all hell, I know it needs a valve adjustment, and what with this engine still running with unhardened valves I want to protect them as well as I can. I've purposely avoided going on any long trips because of this.
Problem is, my car has the older valve adjusters with the lock-nuts on them. I tried doing adjustments awhile back and couldn't do it. No matter how hard I held my screwdriver, the adjuster would always want to turn with the nut as it's tightened.. throwing off my adjustment. I know they had an old combination tool for working with these back in the day but I don't think they're around anymore.
A friend of mine on youtube Rpeek, sent me some of his old rocker arms, he has the newer type that are just really tight screws that you can adjust and be done with. Problem is he only gave me one rocker-arm worth so I need more of them and I'm not really sure where you can buy adjusters online. Maybe some of you guys have some you aren't using?
Though my main question is, will the non-locknut type adjusters fit into my rocker arms that use the lock-nuts? They look like the exact same type of rocker arms.. but I'm not sure.
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By Ted - 10 Years Ago
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Unfortunately the later model interference thread adjuster studs cannot be used in the earlier non-interference threaded rockers. The threads in the earlier lock nut style of rockers is a standard 7/16-20 thread while the later model rockers use a special interference thread design to work in conjunction with the interference threaded studs.
The key to adjusting the lock nut style adjusters is to find the amount of additional twist that the adjuster turns when tightening the lock nut to compensate for the movement of the adjuster stud. Once you find that amount of twist, then you can make allowances for the extra tightening of lash that occurs when tightening those lock nuts. Due to the interference threads becoming looser after being adjusted several times, the lock nut style of rockers will prove to be a better rocker arm in maintaining valve lash over the long term.
Here are some past threads discussing the interference thread design.
http://forums.y-blocksforever.com/FindPost115322.aspx
http://forums.y-blocksforever.com/FindPost115360.aspx
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By Half-dude - 10 Years Ago
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I kinda wondered if that would prove true, the locknuts holding the adjustments longer. Okay.. well that makes me feel a bit better. Do the lock nuts need to be torqued? Or would you say just to tighten them as tight as you can get them by hand? I don't wanna break the rocker arm or bearing by twisting on the thing too much.
Also, just so I'm sure I'm right. Getting the valves to TDC you need to do this right?
Do Intake - When Exhaust Valve is just opening
Do Exhaust - When Intake is almost closed
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By charliemccraney - 10 Years Ago
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They don't need to be torqued. I wouldn't go as tight as you can get them, either. The torque applied doesn't need to be much, probably actually somewhere between standard 5/16 and 3/8" bolt torque. Easy to achieve by hand, yet easy to overdo.
For what it is worth, Harland Sharp say not to exceed 20ftlbs with their adjuster screws.
Regarding valve adjustment, I just set the engine at the tdc mark on the damper, determine if #1 or #6 has the loose rockers, indicating it is at tdc on compression, adjust intake and exhaust for that cylinder, then turn it 1/4 turn at a time while following the firing order until all 8 are done then I go back through one more time to double check.
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By DryLakesRacer - 10 Years Ago
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Just a suggestion, since the adjuster does turn with a wrench remove it completely. Put the adjuster threads in a vice between 2 pieces of hardwood or copper if you have some and then remove the nut and clean every thing with a wire brush. This has always worked for me with old GMC/scrub 6 adjusters and I've done hundreds this way.
A small amount of heat by one of those butane torches ( crack pipe lighter as seen on TV ) from Harbor Freight on a flat of the nut will work too.... Good luck
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By Doug T - 10 Years Ago
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One of the problems you may have with an older engine is that the rocker arm surface that contacts the valve can be worn. This picture shows what the wear looks like after you get the rocker arm assy off the engine. The worn spot can be quite a bit lower than the rest of the rocker arm contact surface but the feeler gauge will "bridge" worn spot so you will not get a true lash reading. This is just about impossible to see without removing the rocker arm assy.
You can use an angle grinder to restore the contact surface to coincide with the worn spot with very careful grinding. Do not grind the spot itself. You can do this without disassembling the rocker shaft assy. I did this on an older engine and it quieted it down a lot.
There was also thread on this site by a guy who did it with a grinding wheel mounted in a drill press with a fitting he made. But I think he disassembled the rocker shafts as well.
I also second Charlie's method of adjusting the valves with the engine warm but not running. This is much much easier than trying to do it on a hot running engine.
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By Half-dude - 10 Years Ago
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You're making wish I'd looked for wear on the rockers when I had them off the engine!
I'm guessing there isn't too much wear, the engine only has 36,000 miles on it and it was very well taken care of.
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By Park Olson - 10 Years Ago
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You can buy, or make a wide blade screwdriver with tabs on either side so it won't slip off the adjuster screw.
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