Building a 273

The 273 is a good little motor. However, it’s a bit endemic in the low end due to cubic inches and compression. The 272 2 barrels came with an advertised 8.8CR. This coupled with the weight of your car and a high rear gear ratio will make the the car sluggish especially with street driving.

I’m currently building another 273. This motor is destined for my 66 Valiant. I’m keeping the flat top pistons and with .028 head gasket and a little off the deck Im looking at around 9.2-9.5CR. On the heads I’m running 920 castings. As with my other 273s I avoid hardened seats by running 1.88 stainless valves cut down to 1.84. With the .030 over bore there won’t be shrouding. Been my experience that running stainless valves it keeps the combustion chamber cooler thus really no need for hardened seats. I do run a little additive in my fuel which helps. If you plan on doing any towing and traveling at higher elevations you’ll want to run the hardened seats. A leaned out motor is killer on the valve seats.

The camshaft was ground by Oregon Cams using the solid Isky E4 profile. Really good grind that helps in the low end. Also running the stock dumb bell lifters. I had those resurfaced by Oregon Cam.

Running the 340 oil pump

Intake will be the Edelbrock LD4B and a Carter 9636. Of course a good electronic ignition.

If you can find a good set of 302 castings they’ll be a good addition to your motor. They tend to flow equal to or better than the unmodified stock 920 castings.