This is kind of a newbie question.

[lillightingboy21]

I have never put my cars piston at bdc. But i heard you are suppose to and it will make engine last a little longer. But how do you tell if it is at bdc. I tries to use the search function but i couldnt find anything that helped me with this. So if you could help me please do. Thanks
Lata,
Nick

 

[gutterboy]

I am not real sure what bdc is cause I am still a rook. I was told that after you run your motor you should make sure that you piston is at its lowest point. Something about it would cause some kind of ring on the sleeve and it would not get good compression. Now that is what I heard, and I am sure someone will correct me if I am wrong. I hope this kinda helps you out.:dumb:

 

[lillightingboy21]

Yea that is wha t I'm talking about. It is bottom dead center(i think) I'm not for sure but that is what I'm talking about.

 

[solman989]

I am trying to break in my engine and am wondering the same thing, but heres what I remember reading from another thread. You can try rotating the flywheel, and when you feel a good amount of resistance, the piston is at TDC. Rotate the flywheel just slightly past TDC until the resistance is no longer there. From here, rotating the flywheel 180 degrees should give you BDC. It makes sense, but does anyone know an easier or more accurate way?

 

[Error401]

BDC is bottom dead center, or the lowest that the piston can go in the cyliner. As far as I can tell, the reason that it is suggested to put it at BDC when you're done running for the day is twofold. First, it's so that any unburnt fuel isn't trapped in the head space, and allows for any moisture to escape through the exhaust port. Second, and more importantly, BDC is the point where there is the most gap between the piston and cylinder. If the piston is at TDC and it cools, the cylinder might contract (from cooling) faster than the piston (due to different metals and their expansion differentials) and thus might deform the cylinder and cause premature wear, or cylinder deformation. I could be wrong, but that's what makes the most sense to me as to why it is recommended.

As to how to put it there, find TDC and rotate ithe flywheel180 (or there abouts). It doesn't have to be perfect, just pretty close. You can do it once and mark the flywheel. Then after that just put the markat the same place and it's at BDC.

 

[KnightAzul]

I had the same question a little while ago, here was the answer:

When the engine is cooling (there is a long time between refuels or the end of the day) the piston should always be in the BDC (Bottom Dead Centre). A good way to see if the piston is in the BDC position is to remove the glow plug and look down the hole at the piston and use your thumb to move the fly wheel, this is about the only reliable way to make sure it is there.

Also as a quick and dirty alternative you can move the fly wheel until it is at the point of least resistance.

Hope this helps!
KnightAzul

 

[olds97_lss]

From the opinions i've read, you put it at the bottom of the cylinder so when the sleeve cools, the sleeve shrinks as much as it possibly can. If the piston is at the top, it won't shrink as far because the piston is actually larger in diameter than that part of the sleeve at room temperature. This is why an engine wears out, or at least mostly why. As the engine runs and gets up to temp, it's actually wearing out the piston and sleeve since the sleeve hasn't expanded to it's running temp diameter. It's essentially grinding away the piston and sleeve at the pinch point (tdc). This is why you want to get to running temps as soon as possible.

Running too cool will prematurely wear your piston/sleeve out as well. These things are designed to be at optimum clearances around 200 degrees.

I read a lot.

Hope this doesn't make it more confusing.