Interpreting a Sonic check - help!

[undy]

Originally Posted by SantaFe66

Undy,

Since the 390 is .030 over now (4.080) and .050 over more would make it 4.13, the thinest wall would be .125 (1/2 of .050). The shop that did the sonic is a reputable race motor builder (albeit small blocks) and he recommended to not go below .100 wall thickness and, since mine wouldn't, to go for it.

I'm concerned about overheating too. I live in a small town with a stop light at every corner so getting from one side of town to the other is an exercise in potential overheating. I seem to have solved that with my current set-up but this would take me backwards.

Stroking the .040 over engine with a 4.125 Scat cast crank and associated rotating gear is the most costly solution but certainly has the best chance for HP and TQ as well as cooling. You're probably right.

Thanks.

my bad, didn't read about the existing 0.030" over-bore..

Looking at the readings you probably could do the 0.050" bore and have enough wall thickness. The readings reflect a reasonably consistant thickness throughout, not enough to cause worry about thin spots. Casting porosity would be the main thing that I would worry about. If I really wanted a "428" so bad I could taste it then I'd probably go for it. The more "rational" (Who's rational?? That's why we choose the cars we do) approach would be the minimum bore required to clean everything up and get a "main-stream" size/mfr piston at what ever stroke you decide to go with.