I wouldn't go 0.040 over on a Subaru block for any application certainly not one that is seeing the thermal stresses that a car being tracked is!
Running 0.020 over on a 500whp car with sufficient cooling for track use (both oil and water cooling that is) led us to find the following.
We would have to pull the motor after each event, every inspection lead to the same results. Bearings in perfect shape (could be reused if we wanted) at least a 20psi variance in compression test numbers between one of the holes (injectors always flowed and balanced, we had 4 sets for the car at the time) cylinder ovalization was apparent in the hole with lower compression. No sign of detonation anywhere!
We endured this for our first year of TA in our car. Until Darton released their full size ledged sleeves following that we now rotate and refresh every 4 events or so.
Something other findings to note,
Stock rods tend conduct random block oil changes at around 500whp.
10:1 compression yielded very unimpressive results regardless of fuel quality used.
After 600whp certain modifications become necessary to the block to keep the halves from walking around the crank.
Factory water pumps cannot be turned by hand with 10psi of pressure in the cooling system (take a look at the pulley on the WP to see if you have any tale tails of the belt skipping).
Removing the factory WP nets a decent gain.
90% of research we did online while developing the motor to where it is was as useful as a ash tray on a motorcycle!
Mike
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