Information on the 273

The development of the 273.

They took many off the shelf parts from the A engine Poly 318 to save money. They modified the block casting a bit. They made new heads for the 273. They used the same Poly 318 Dizzy, timing chain cover, oil pan, forged crank and forged rods but for the simple fact the 273 piston was so much smaller and lighter, they had to add some 'BOB' weight to the piston.
So they put in some THICK wall connecting rod pins (Wrist pin) to bob weight the pistons the same as a Poly 318s piston. From memory, I do not think a 5/8's drill bit will fit inside the 273 wrist pin, its that big.

Put some modern tech light con rods in the piston and shave 5 pounds off the crankshaft. NOW TALK ABOUT A REV MONSTER! With proper valve springs you have a 8,000 to 10,000 RPM engine.

Bore it 0.040" and put a 4 inch stroke crank and have a 340 Ci

Rumors back in the 70's was you could not put a hyd cam in the 1964/65 273. WRONG!

Edited for Wrist pin.