Quote:
Originally Posted by Adger Smith
To help answer Rod... The clearance in the groove is not real important with Tru arcs. It is as Dwight says, The total clearance with the pin. Years (& years) ago I cut them in some pistions we used for Dirt racing engines. Because the piston grows more than the pin I always tried for "0" clearance in the pin to lock. I never cut them with more than .004.... When the piston gets hot and clearance develops and the tune up isn't right, (unhappy engine) the pins can batter the locks out. Another important thing about the Tru Arc is proper installation.
As stated in earlier posts the flat/square side out. If doubled install the rounded together. You should always put the open ends of the Tru Arc at the 3:00 o'clock or 9:00 o'clock positions. With the opening at the top or bottom the lock can crawl/slide up or down in the groove at high Rpm. That movement will close the open end just like you had a set of pliers pinching the ends together. When the piston stops (dwells) at TDC and BDC The Tru Arc can flip it's self out.
That last tid bit is why they got a bad rap as being no good....
BTW I also built a fixture to hand drill the pin oilers in those older TRW pistons. That was another problem we had to work around back in the golden/olden days... What about it Dwight? :~)
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Hello Adger
I still have my home made pin oiler also. Back in those days, I feel that was what gave clips their bad rap. As pistons were made back then, this industry was going thru growing pains. We were doing things with pistons that these companies had no thoughts of. Since most pistons did not get adequate oiling, they would partially seize and batter out the clips. Hell we could have pushed any type retainer out. And if you ask any piston manufacuter to day about clips. most of these engineers dont even know what a clip is therefore they will tell you it aint no good cause they aint even seen one must less tested one. I have worked in industry for 34 years and have worked with some super high dollar pistons in cylinders and not one has ever had a spiral lock in it. Most either had tru arc or wire clips.
reed