So I'm building up my new block (84mm 9.0:1 Supertechs, Carrillo A-beams), and it's time to attach a piston to a rod. The wrist pins fit in nicely, now I need to install the circlips to hold them in place. Buh? These aren't snap rings! How are you supposed to get them into the grooves in the pistons?

--Ian

 

put one corner in & slowly push it around until you get the the other end & clicks in (are you sure you want to be doing this if you cant install circlips)??? no disrespect maybe find a mate that has done this a couple of times, you dont want a motor letting go after you have put your hard urned cash into it.....

 

i agree with sprx3, i wouldnt trust my self, if you search theres a few post about wrist pin failure due to wronge tolerance. it seems pretty common that they need to be checked and machined for proper fit.

 

Try this spirolock tool, it is available in both plastic and steel:

The Lock In Tool - A piston locking tool for installing spiral wrist pin locks and wire wrist pin locks

 

All you need is a pair of needle nose pliers and a brain to install them.

 

OK, got the first one in. Bent needle-nose helped a lot -- it only went springing across the room once.

Why don't they use snap rings? From googling around, it seems like lots of folks have problems getting them in, and I'd think snap rings would be whole lot easier.

thanks,
--Ian

 

Because that would be way too logical, and we can't have that.

 

When I picked up my block from the machinist he specifically warned me to be careful with the circlips. There must be some magical property a circlip contains that makes it better for the application than a snap ring.

 

Does the piston have pick lock grooves? It's a relief cut from the outside of the pin boss tower parallel to the pin axis that intersects the lock groove. If so, what you need is a straight pick or a small flat head screwdriver. Put the lock partially in the groove (it will only go in so far without compressing it) with one end of the lock completely overlapping the pick lock groove. Hold the lock partially in with one hand, put the pick in the groove with your other hand (groove acts as a pry location) and use the pick as a lever to compress the lock and slide it in at the same time. If that doesn't make sense I can take pics at work as I do it.

 

OK I'm having the same trouble. The stock pistons circlips are super easy with round x-section needle nose pliers. I tried the same technique on the Supertech pistons until I scratched them up.

iWeasel, is the technique you describe similar to that in the first half of the video on this page:
How to use the Lock In Tool

 

I ended up using a whiteboard dry erase marker whose diameter was close to optimal.

But not without scratching up 2 pistons. There is a technique to it that takes a while to get right. It is similar to the video.

 

Hmm.

Seems like the sort of tool that someone with access to a lathe could whip up out of Delrin for about $3.98, plus shipping.

 

Here's a pic tutorial of how to put in wire locks:











No it's not a Supertech piston, it's an OEM Mini Cooper S.