What do you do to break in an engine.

Well, this is a very contravercial subject, but from my research, I have found this.

Here is what you do.

With the engine in the car, Run the motor as slowly as you can and very rich, for about 2 minutes, then let the engine cool completely, then run it as slow as possible for another 2 minutes then let it cool completely, continue this for about 3 tanks. REMEMBER that when your motor stops to cool, make sure the piston is at the bottom of the stroke. Once you have completed this, then start to cycle the engine in the 2 minutes by taking the revs slowly to about a 1/4 throttle, then down, let it cool again, do this twice, then take it to half throttle and down, but remember to be progressive, smoothly up, and smoothly down. Let it cool, do this twice, then to 3/4 throttle and down, do this twice, you are now ready to start to lean it out and get it up to race tuning. Remember to change your plug when you have finished.

Start the engine with the general settings. After it is running, open the HSN 1/4 of a turn at at a time until the engine starts to load up, then turn the HSN in 1/4 of a turn in and let in run at idle for at least 1 tank. The idle must be even, if rpm's go down or up, close or open the LSN 1/8 th of turn at a time. Let engine cool completely after first tank, and make absolutely sure piston is BDC during cool-off. Repeat this 4 more tanks and your "heat cycling" idle break-in is done, then it is time for track break-in for 5 more tanks, leaning HSN little by little until you end up with nearly at general setting on the HSN.
AFM

how do u make sure the pistion is at the bottom?

and wuts BDC?

You turn the flywheel with your finger and you'll feel the piston loose at BDC, if you keep turning you'll star feeling it getting harder as it moves on to compression towards TDC (Top Dead Center

BDC = Bottom Dead Center


afm