I'm gonna refresh my engine installing a new piston/sleeve set, and obviously i'm also installing new bearings and rod.

Question is: should i breakin the new P/S with old bearings and old rod???

Some mates told me to change P/S first, and breakin them with old bearings and old rod, with the purpose of not giving too much stress to the new ones.

This seems to me the right thing to do, but i'm also wondering if old bearings and old rod, with no more perfect tolerances (play), could affect negatively how new piston and sleeve adjust to each other..

What do you think and/or usually do?

Thx 4 advises

It is a good idea to run in the P/S set before changing the bearings indeed of the forces while running in. But a new P/S set, rod and bearings.... I would say you are not far off the price of a new engine.

The reason for not reving quickly during the breaking process is that the bearings also need time to run in or the balls will drag against the race and make them prone to premature failure. I personally just run them all in together HOWEVER I leave the old rod in there for the first 2 tanks because those are the worst ones on the con-rod. Thats just my take on it.

all new

a couple things about break in , if you have to loosen the glow plug the engines not warm enough , if you have to turn the flywheel with a prying device the engines not warm enough

preheating your new engine and keeping it in a certain temperature range during break in is very important when done properly there is no need to replace rod after a gallon of running as you have aleviated most of the stress on the internal componenets with the heat

i myself have incorporated the comp heat engine block heater into my break in program and am loving the results

Suggested cool down temps between tanks? I saw mention of "a certain temperature range" and was wondering what that is, in general.

The reason I ask is because it's easy to leave the heater on and just unplug it....especially when some are idling on the box through the first few tanks. Normally (not using a heater) I just wait at least 5/10 minutes with piston at BDC. Then reheat to over 200 with a heat gun before restarting. I don't track cool down temp...if I can hold the head it's cool enough for me.

Ambient temps

You should be fine breaking in with the new bearings and rod as long as you take it easy the first 4 tanks or so...

Best procedure I've seen..

Search YouTube "Best Nitro RC break-in Procedure!!!!"
User is nitromad48

+1

My thoughts:

If you had a new engine, would you tear it apart, put in used bearings, break it in, tear down, then put in the new bearings?

OOOOk, thanks everyone for your thought, even if some is saying the opposite than others.

Good point. No I would not, but someone replace them all after break-in, and it's the same.

Of course I'm gonna preheat it, but are you sayng that if I leave it runnin at high idle and quite rich for right lubrification, and if temps don't stay high I've to "help" them using heater while running?

When you are breaking in an engine it needs to run rich and at 220 or higher use a heat gun and alum foil or an engine heater run it for 5 mins or so and then turn it off return the piston to bdc and let the engine cool all the way down. It usually takes 20-30 mins to cool then repeat. Personally I do this 5x then run it on the ground at 1/4-1/2 throttle with the head wrapped to keep the temps up 220+ a complete tank, let it cool and repeat. I do this until I have 6 tanks through it. Then I take it to the track and let it rip. Works for me. But you have to let it cool completely in-between cycles

proper temeperature , quality fuel and not over reving a new engine are very key components to a proper break in