Not absolutely sure but I think the notch goes on the cam side. There are three heads for the 270. The old style dome chamber with small ports, the old style dome chamber with big ports called the H head, and the later sort of D shaped chamber but not like the 302 D chamber. The late 270 head has small ports. Of course different chambers could use different pistons. Sadly 270 pistons are becoming hard to find. The small ports are adequate for for ant street engine.
THANKS for the reply! on the notch it runs parallel to the pin so it can't face the cam side. my pistons are flat toped with a slight dish. my head has D shaped chambers and the large ports, i believe its A 302 head. i'm going to figure static compression today, and as long as its not to high i'll be good, i'm going to run a turbo so anywhere around 6.5-7.5 would be good. with the waste gate set at 10-12 psi. 6.5 @ 10 psi will be 10.9 at full boost. this is going in a 31 chevy pickup. i'm just in the process of assembling the engine and was wondering about piston configuration. is there a right and wrong way they fit in the block? i can see no difference in pistons OTHER than the notch. one of my main problems was that i bought a pickup load of GMC parts and trying to make an engine out of the basket of parts. i have what looks like a freshly bored and decked bock and a set of nearly new looking .030 stock pistons that fit the block as they should. so far i have the crank installed and ready for pistons. just got the head back from the machine shop after a complete rebuild.
Jay D.
