engine rebuild

[tbbh-teacher]

When rebuilding the engine the half moon cut out on the piston does that go toward the exhaust are the carb. Thanks

 

[.21Rc10GT]

Pretty sure it goes towards the carb side. Make sure the little hole in the bottom of the connecting rod is towards the carb side too!

 

[tbbh-teacher]

what is that hole for?

 

[Plaidfish]

Lubricating the bushings in the conrod.....the oil will follow the channel in the conrod to that hole....if it's not channeled then you may have a hole in th ebottom of the conrod....just make sure it's not offset, if it is then you need to know which side of the conrod faces out

 

[Pinblaster]

The hole in the side of the piston is for the boost port in the engine and it goes to the carb side of the engine. The engine will run with the piston installed either way but it will burn up the piston and sleeve in about 3 tanks if installed backwards.

I was lucky enough to witness it happen rather than experience it, so it didn't cost me anything to learn that lesson.

 

[Plaidfish]

the guy didn't hear the thing bangin away???
I put my VZ-b in Backwards and it sounded like a hammer every time it came down.....more like jack hammer.....

 

[Pinblaster]

no, it was on an OS .12cv, he had the sleeve in right but the piston was flipped 180 deg. and it ran fine for a while. after break in and running a couple of tanks at tune, it lost all compression. he pulled the piston and sleeve back out and you could slide the piston about 1/8 inch above the top of the sleeve. then he asked which way the hole on the piston goes, and realized he put it in backwards. but it never made any noise and it ran good while it was running. I think he said it was a Duratrax piston and sleeve, that may have been part of the problem too.