10.5:1 pistons

[S14DB]

Don't forget the 2ZZ Celica.

It really has to do with your Effective C:R. Actual C:R+ Forced Induction. Most modern motors start failing around 18:1. So, a C:R +1 or 2 isn't as major as one thinks.

Also, Pentroof and cyl design has changed radically since even our motors were designed. A lot of the 8.5:1 fokelor comes from OHV V8's that have horrible quench areas and are comparatively prone to pre-ignition. 10:1 and 11:1 are race gas only territory. Has anyone seen the piston on a SRT4? Looks like it's from a High C:R NA Race motor. Not a turbo street car.

What I'm trying to say is that people here are arguing Apples and Oranges. Our KA's are more modern than SBC's but not as radical as 305z, K-Series, 2ZZ's. They run great to 400ft/lbs @ 9:1. When the thin ass ring lands give way. Certainly can handle more power with better piston design.

On the subject of Piston Design. Most 8.5:1 pistons dish out. Keeping the flame front away from the ring lands. At the cost of some of the quench characteristics of the head. How do the 10.5:1 raise the C:R? Do they just make the stock piston taller? You can do that by decking the block. Or do they raise the center of the piston to match the shape of the head?

My point is that there are lots of things to consider when changing the C:R of a motor. The Head and piston design are more important than any general rules.