I installed 1.7 roller rockers on a 69 427. followed the instructions to the "t" on how to tighten and adjust the lash. the final step is to tighten the set screw down in the middle of the polylock. I have done so and was in the process of running the engine for the 30min break in period per the instructions when the motor died. I pulled the valve covers off readjusted the valves (since the lifters were now pumpesd up) while doing so i noticed that several of the polylocks were loose but i figured it was a change in the lifter pressure that loosened them. So I restarted the motor and was letting it run when it died a second time. I removed the valve cover and this time one of the rockers was sitting sideways and the push rod was down in the motor. I removed the pushrod and noticed the lifter had been pushed out of the guide hole and was laying in the top of the motor. After a few tense moments I was able to remove the lifter with a magnet. Upon removal i noticed the lifter had completely come apart and all the pieces were laying in the motor. I extracted all the pieces and was able to install a new lifter via magnet and a fishing expedition. I again adjusted all the valves but the polylocks still come loose!!! even with the set screw tightened.......am I missing something here? Shouldnt the set screws hold the polylock tight? the polylock coming loose is what caused the catastrophic lifter failure.

 

The guy at the machine shop that did the work on my engine said to adjust the rockers at zero lash, add your 1/4 or 1/2 turn (in my case it was 1/2 turn - roller rockers and roller cam) and then tighten down the set screw with your box wrench still in place. Once the set screw is as tight as you can get it with the hex wrench, give the box wrench a slight bump to tighten down the lock a little more. This locks the set screw in place. Did this, but haven't fired up the engine yet, so will have to wait to see if it works. Hopefully, this weekend.

 

Are they Comp Cam lifters? I had the top retaining ring pop off one of mine when it was brand new.. Luckilly I found it and replaced it..

 

yup they sure are.... the whole thing exploded. I just happened to have an extra brand new one from another project that I was able to replace it with. Even the side of the lifter broke and i was fishing little tiny pieces of metal out of the valley and piecing the lifter back together to make sure i had everything

 

My engine builder told me its not the first time this has happened when I called him about the problem.. I know my next motor wont house any Com Cam lifters.. As for your orginal question, when I went to replace mine, the locknut was so tight it bent my allen wrench.. I have had the locknuts come loose on me before but that was when I tightened them myself but after seeing what an expereinced engine builder did, I'm starting to believe you really need to torque them down. Comp Cam also recommends zero lash with no more than an extra 1/8 turn..

 

Here is the STRAIGHT SCOOP from a SOLID LIFTER Vette owner. You need to make sure the tops of your rocker studs are ground FLAT and if they aren't you can take a cuttoff wheel and grind them flat using a old nut as a guide to get the tops SQUARE to the threads. When you tighten your poly-locks to your lash point, back them off about 1/8-1/4 of a turn, run the set-screw down and TIGHTEN BOTH the set-screw and poly lock nut at the same time. The set-screw in the poly-lock should make an impression on the top of the rocker stud when done properly. Sometimes you can tighten the poly-lock so tight that the rocker stud gets pulled out when you back it off at a later time. This all being said, I would have concern for any motor that spit a lifter out of the lifter bore because it created one HUGE oil leak and may have caused other motor damage.