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I use Scorpion rockers on my BBC with a Crane girdle. Solid roller cam around 714 lift. While adjusting the valves recently I noticed side play in the rockers (while the individual valves were closed) as if there was a small gap between the rocker studs and the hole in the trunion of the rocker. All valves were adjusted correctly...how much side play is too much? The trunions appear normal and solid and no loose bearings.:idea:
Sounds pretty normal to me. If you had just one that was way out compared to the others you might have a problem. Chances are they didn,t all fail at once. Mike:idea:
It is possible that the rockers have too large of a hole. It is more likely that the rocker is not far enough down on the shank portion of the stud. If you have only 5 or 6 threads showing this is probably the case and you need different/longer shank studs. Even shorter pishrods in combo with the studs. If the wear pattern on the tip of the valve is centrally located and narrow (.100-.150" ) then your pushrods are pretty close and you may want to round up different studs. If none of this is the case, measure the hole and stud shank. .002-.010" is normal clearence.
Are you certain the slop is not lateral (sideways) in the trunion bearing area? The trunion will have a retaining ring on each side, and will NOT be locked tight on both sides. Several thousandths of room are needed to insure against binding. The lateral slop does no harm anyhow, unless the bearing is so loose that it allows the rocker to tilt, not just slip sideways.
I will check all of the points that were brought up. Thanks for your input guys....give me a week and I will get back and let you know what I find out. Would be sooner, but I'm being sent north to the Santa Barbara (Zaca) fire.
Well, I'm back. I pulled the covers and did some checking. Rocker Stud dia. came in at .432 thou. and the hole in the trunion came in at .437 thou, so .005 is not bad. The trunion bearings were tight, but the end play was in the neighborhood of .008 thou. A little tough to measure as my calipers were not quite deep enough to grab a good measurement area, but very close though. A few of my lock screws would loosen after a few passes last race,hadn't happened before and the girdle kept things in place. Time to replace the nuts. Thinking a new set of ARP's this week.:D
Picked up the new Rocker Nuts. Minor problem.....situation, really. On the main body of the rocker nut it transitions from .750 to .600. My old nuts transitioned with a 90 degree lip the ARP's are radiused. This added bit of material strikes the side wall of the inside slot of the rocker. An afternoon of filing should take care of this....
Picked up the new Rocker Nuts. Minor problem.....situation, really. On the main body of the rocker nut it transitions from .750 to .600. My old nuts transitioned with a 90 degree lip the ARP's are radiused. This added bit of material strikes the side wall of the inside slot of the rocker. An afternoon of filing should take care of this....
Sam if you can file the end of the nuts it would mean they are soft. I think that area is heat treated, (I could be wrong but I think they are ground after heat treat)......What you needed was a thread gage, a "GO" "NO GO" gage to actually check the threads in the old nuts. I have switched several rockers and nuts around and havn't ran into this 90 vs radii problem....yet......Ray
Hey Ray...when are we going to plan a day at Casitas and wake the fish again?
What I meant by filing was a small amount of aluminum from the inside edge of the rocker NOT the adjuster nut. Much rather file soft metal instead of hard. Won't need to take off but a small bit just to clear the radiused edge of the adjuster nut shaft. Make more sense..?
Hey Ray...when are we going to plan a day at Casitas and wake the fish again?
What I meant by filing was a small amount of aluminum from the inside edge of the rocker NOT the adjuster nut. Much rather file soft metal instead of hard. Won't need to take off but a small bit just to clear the radiused edge of the adjuster nut shaft. Make more sense..?
Sam, Gary is closest to being ready for a test and tune session.....My next few weekends are kinda busy, BHC/maybe Phoenix/Bonneville/BHC/Ming/Parker, a little tight............Ray