sprio locs

[GJCAT427]

Do you need to run double sprio locs on piston pins? I`m putting trw 2299s in my latest 427 and the retainer bore is set for .040-.042 tru arcs retainers. If you double the sprio locs they measure .080. I went looking for thicker spiro locs but haven't found any thing that works yet. Give me some options guys.

[gt350hr]

  Be very precise on the lock width measurement. TRW used to use a .052 wide Tru Arc and using an 042 spiro lock would allow too much end play and possibly push out  the spiro lock.
    Randy

[GJCAT427]

I just remeasured one of the true arc and come up with .045. It fits the piston grove tight, but I still wondering if they make a sprio loc in that size or if I can get 2 that fit the groove. If I double the sprios up it comes in at .082. That aint gonna cut it. This is going in a TP so I`m being careful on the assy. I did have a tru arc pop on one of my 427s yrs ago and it cost me a pair of liners on a standard block. It also wound up cracking the valley when the machine shop pressed the liners in. Not happy and I bitched. They claimed it was already cracked. It wasn't and they owned up top it when I had proof.  As you can see I`m leary of the tru arcs but I`ll use them if all else fails. 

[gt350hr]

  The big problem with tru arcs is they break off the eyelets right at the point they are the thinnest. That alone can cause engine failure. Lock grooves are cut ( typically) .044 wide for a single .042 lock , 055 for a .052 tru arc. .075 for a "triple wound" .073 spiro lock or .088 wide for "double" .042 locks.  Substituting ANY lock other than what the manufacturer specified is dangerous. Careful measurements MUST be taken on the locks being substituted .
   Randy

[GJCAT427]

Any Idea where I can find the TRW specs for the pistons?

[gt350hr]

  If they say TRW the locks need to be .052 wide tru arc style. They are difficult to find these days even with the original lock part number.

[winr1]

These are the same dimensions as the c clips that came with my Speed Pro forged 390 pistons

LR-N540098


https://www.summitracing.com/parts/slp-lr-n540098

here is a post I replied to

https://www.fordfe.com/stock-type-tru-arc-pin-clips-t110250.html


Do your pistons look these ??

https://www.supermotors.net/registry/media/962077


Ricky.

[GJCAT427]

winr1, my pistons are exactly the same as your showing. I got mine from John V. I also got 2sets of the same but they are dykes rings on the top rings. Need to come up with 16 top rings for those sets. I have the OEM ring #s but can`t locate any.

[gt350hr]

  You could have the top ring grooves re machined for 1/16th rings and be fine. There will be  a .011 step at the top but several piston companies are doing that on all their pistons calling it a "gas distribution groove". It works to promote better ring seal. Rebco Machine it Wichita KS can do the machining of the top ring groove and it is inexpensive and perfect work. He has several Youtube videos showing his work. I have used him many times over the last 30 years and never been disappointed.
    Randy