NHRA Horsepower Ratings for the 273

Dart 4 Forte,

If you mill the cylinder heads, and a get to 57.3 CC, and the deck block is
trued with a piston height of .129", the compression ratio should be in the range of 10.5 to 10.8

As for the stock 273/235 HP valve springs, they had a thicker coil than the 273/180 HP 2-barrel engine.

We found that out the hard way.............