J-Spec "break-in"?
 

I'm just about to put in my second j-spec(the first died of dirty injectors :( ) My question is, whats the accepted "break-in" procedures for a used motor? First time around i put about 200 miles on it then i threw it on the dyno. Is that too soon? Does the weight of the oil matter during "break-in"? I'm in Salt Lake City and it gets hot so i plan on using 20w-50, at least during the summer. I realize the motor is actually broken in already but it doesn't make any sense to throw it in and get all over the throttle, so i'm looking for intelligent opinions. Should i run some atf through it or mmo? Not that it makes any difference but the first one started the first try, and ran great. Appreciate all your help.

the only "break-in" need that i'm aware of is when you actually have a rebuild, so you can have the seals seat and build better compression.
however when i installed my s5 TII jspec engine, i drove it around for about 100 miles before romping on it. i also was premixing duringt his time to make sure everything was that much more safe...
just my 2 cents.

I am pre-mixing as well. A couple hundred miles should be fine then. Thanks for the input.

I pre-mixed about 5 gallons with MMO to get started.
I also squirted about 2 oz of MMO in the lead plug holes & cranked it a few 5 second spins.

Compression evened up after about 50 miles.

After I saw the MOP was good with no check codes I gassed up & hit the redline.

How much mmo did you use in the gas, i almost have a full tank( the last motor blew up on the dyno, i filled up before i went to the dyno)

I used about a pint in 5 gallons just to start.
It smoked a lot, but didn't foul the plugs.

When the idle smoothed out about 50 miles later, I filled it with straight gas & boogied!

Usually jspec engines sit for a while before you get them, so I would suggest running it smooth for about 50-100 miles and a bit of atf wont hurt it either....