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Dwight Southerland · 09-21-2012, 08:24 AM

I haven't read much from the engineering side about pin locks, but what I have read says the round wire locks are the best. I do know, as you say, that all the American manufacturers use Spiro locks and that TruArcs are very difficult to get through them. I am not a TruArc bigot, so I just go with what ever, though Spiro locks are such a PITA. I personally have never had a lock come out so I cannot say anything other than they must all work pretty good.

I had a piston engineer at Venolia tell me years ago that clearance between the end of the locks is much more critical when using TruArcs; that excessive clearance contributes to pounding the locks and that TruArcs will give before Spiro locks. That seems common sense when you look at the difference in construction. Maybe that's where all this got started - the result of sloppy machine work and tolerances. I know that Chevrolet used a single TruArc in the '69 Z28 engines and that Traco used OEM pistons in their TransAm assemblies with no mods. The aerospace industry also uses single TruArcs in lots of critical assemblies that undergo similar stresses.

09-21-2012, 08:24 AM	#6
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 1,999 Likes: 64 Liked 773 Times in 192 Posts	Re: pin lock ? I haven't read much from the engineering side about pin locks, but what I have read says the round wire locks are the best. I do know, as you say, that all the American manufacturers use Spiro locks and that TruArcs are very difficult to get through them. I am not a TruArc bigot, so I just go with what ever, though Spiro locks are such a PITA. I personally have never had a lock come out so I cannot say anything other than they must all work pretty good. I had a piston engineer at Venolia tell me years ago that clearance between the end of the locks is much more critical when using TruArcs; that excessive clearance contributes to pounding the locks and that TruArcs will give before Spiro locks. That seems common sense when you look at the difference in construction. Maybe that's where all this got started - the result of sloppy machine work and tolerances. I know that Chevrolet used a single TruArc in the '69 Z28 engines and that Traco used OEM pistons in their TransAm assemblies with no mods. The aerospace industry also uses single TruArcs in lots of critical assemblies that undergo similar stresses.