Getting powerhead back!

[seebold1]

Well I am getting my powerhead back from the machine shop, where i had it rebuilt from from crank up, all new... the machine shop where i had it rebuilt (CMSI) has some pretty stiff breakin rules. 10 hrs no more then 3500 rpm's... I am running a 30 wheel, should i use a 28 wheel on breakin... I would like to aleast get it up on a plane for the 10 hrs. It will be a long 10 hr's plowing along!:rolleyes:

[TB21]

just my opinion , but 10 hrs. is overkill . I'd idle it for 10 minutes let it cool , run it easy but not at any steady speed until it got some heat in it , let it cool and do it again , let it cool then race it. Did they set it up with extremely tight clearance or something , what is the reasoning behind 10 hrs ? As far as break-in i even think the "Don't run synthetic oil during break-in is a joke". But my opinion only. TB

[seebold1]

they say it will void there warrenty... of three years. If you don't follow there breakin proceders... I just think i am going to play it by ear...;)

[TB21]

And do you know how many gallons of gas that is ? TB

[Techno]

I've heard the 10 hours quite a bit. Mine is a 10 hour one with 3 hours already dynoed/breakin. So only the easy 7 to go.

This 10 hours isn't a do the same thing for 10 hours but is a ramping thing. The most important are the first several. There are a lot of opinions on the proper method but basicaly the first few are warm up and cool down with lots of grow shrink cycles. Usually done on the hose and then in the water.
After that is more a mid rpm breakin where your slinking along- eventually with full power short blasts.
The general idea is the engine is heated and the metal expands, breaks in to that. Then let cool- shrink and done again.
If you just blasted out of the hole some parts will expand at a greater rate than others and now its damage instead of break in, wearing of componants.
Metal changes shape when it heats up and again when cooled. Not much but enough.
Done incorrectly you now have a non-broke in engine and further wait and money with a 2nd break in.

Synthetic apparently lubricates too well and doesn't allow the metal to wear. As if no break in was done.

[Showtime]

Tempering new pistons has always and will continue to be a pain. It's always a guessing game, if you have enough time on them. An oven a 400 degrees for 1 hour, can help shorten those long boring rides. This tip was passed on to me by Roddy Prestage years ago, when our drag motors had a short life anyway. All of my pistons life start in the oven....

[TB21]

i've never heard of tempering a piston , are you sure thats the right terminology? TB