Tips on breaking in a rebuilt 540 engine

[44racecar]

Looking for tips on breaking in a rebuilt vmax engine. Thanks.

[YAMMIEGOD 3:16]

mix some yamalube at 50:1 in your gas. 3:16 (yammie tony)

[tyler440]

i believe every word this guy says....
http://www.mototuneusa.com/break_in_secrets.htm

read it...
then run it like you stole it to 3/4 throttle for the first tank of gas... dont start it up until you are ready to rip on it, not even just for a bit...

[killerklown]

Im not sure about this....

[Speednutt]

That is correct. Read it and if it makes sense, then you have been around engines for awhile. If it dont make sense, then you should stick to 5hp briggs. Rock it

[tyler440]

technically 5hp briggs should be run the same way hahaha

that dude has a ton on info on his site that is really eye opening (porting and such) its just a shame he seems to have dropped off the face of the earth

[Bob Vehring]

I think you will find most engine builders, especially for racing engines agree, engines needs to be broken in under the load and temps it will see.
On our dyno which is not for sled engines but its basically the same, at idle, low rpm or no load situations, the engine doesn't really make heat. HP is heat. Metal expands as it gets hot, especially Alum. the hotter it gets, the more it expands
Pistons are not made round, they are made to become round when they reach their max operating temp. This is because there is more material in place like the pin boss and the top, then there is in the skirts. Some areas expand more then others. Now days there computer designed and made so they do become round once everything is fully heat soaked.
The cyl. bore is either all alum or alum. with a iron sleeve, it will also expand when hot. For best performance and life, you want these parts to mate to each other under full operating temp for best ring seal, that won't happen letting it idle or babying it around