MG MGB and MGB GT Tech Talk
I just spoke with a guy at my favorite machine shop. He knew of the "C" clip problem in BMC engines and had seen the "teflon button" fix. He believes they came with a set of Cosworth pistons! Apparantly, another "fix" was to use a spiral type spring that fit in the same groove.
I knew they existed! These are for a VW but I bet they could be modified for a B - Next engine build, I'll try them!
http://www.cbperformance.com/catalog.asp?ProductID=172
(How do you paste a hyperlink in here?)
<http://www.cbperformance.com/catalog.asp?ProductID=172>
Eric: You have to put a < in front and a > at the rear of the complete URL address to make it work. AL Bradley
I have installed too many C clip in British motors to count, and have never had a problem. One problem with them is improper installation. Someone not getting them seated properly in their groove. If they didn't work well in pistons, how could they work in driveshafts? I suppose if you were building a full blown race motor the teflon buttons would be cheap insurance for an engine that will be turning 10K.
I've installed every kind of piston pin retainer you can think of and never had one screw up. Engine building is details details details, other than that, just be super pickey and pay attention to details. Do it right and you only do it once.
I nearly goofed big time installing some wrist pin circlips recently.
I'm rebuilding the engine for a Moto Guzzi Ambassador basket case I got a few months ago, and I recently got around to installing the pistons and cylinders.
I didn't double check the wrist pins and couldn't get this out of my mind, so I lifted the cylinder up far enough to check and sho'nuff a little bit of the wrist pin circlip for one piston wasn't seated in its groove. Whew!
I"m learning as JDW said--details details details.
Like you, I have rebuilt too many A and B series motors to think about, and never had a problem but the truth is that the clips CAN jump the groove under high piston accelerations, and if the clip is oriented "just right". The buttons are used in high revving engines to prevent this. I believe this may have been what happened to Gary and was offering it as a suggestion.
They work in driveshafts because there is very little acceleration on a driveshaft compared to a piston - a piston goes from zero to max speed and back to zero twice per revolution!
I just found out that the machine shop I use can turn them. While I've never lost a circlip either, I'm told that as they wear, they are also more prone to pop, so just for giggles and grins, I'll have some made for the 66.
I have seen two engines destroyed because wristpins circlips failed. On one, there was still an impression on the side of the piston where the wrist pen got wedged between the piston and the cylinder walls. On both, the wrist pens were undamaged, but the piston and cylinder were destroyed. I cannot say positivity that the cause was wp circlip failure just as I cannot say that if you put then in right they will never fail. That said, for my 1950 engine with Lotus TC pistons, I made my own wristpin keepers from teflon. I did this after talking to several people who raced boat engines years ago who used to do the same thing from aluminum. Venolia pistons used to be availiable with teflon wristpin caps as well as buttons in the side of the piston skirts, and they were a thing of beauty
