little 'ol 273

Here's what Mopar did to get 275 hp out of the 273 back in 1966 in the D Dart program.


(from a Mopar tech bulletin)
The "D/Dart" features a modified 273-cubic inch engine with a special four-barrel Holley carburetor. Other features include: A special Camcraft camshaft (284 degrees with .495 intake and .505 exhaust), Racer Brown valve springs, a modified, full-breathing intake manifold, a low-restriction air cleaner, and a Weber clutch. Other standard items are: a heavy-duty 4.86:1 Sure-Grip 8-3/4 inch rear axle, free-flow exhaust headers by Doug of California, a four-speed manual transmission,

I did a rebuild on a '66 Dart Charger 273. Had a very hard time finding the domed pistons in either stock or +.030 sizes. I don't know how well 302 heads will work with domed pistons. The 302 has the smallest combustion chamber of the lot and will not require notching the block for bigger valves.

The original manifold on the 273 4bbl was a single plane cast iron design. It should yeild more top end power. The problem with most aluminum single planes on the aftermarket is they are designed for the larger port heads.

Not sure you can make it to 300 with this motor. Good luck.