Mopar 273 Small Block

If you decide to build a 273 Mopar there are a couple of challenges you'll face. Egge Machine has solved the piston availability problem for the 273 - if you don't mind running cast pistons. Also, at around $300 a set the Egge 273 pistons cost about 3 times as much as a set of equivalent TRW pistons for a 318 or 360. If you want to go high end, Ross will make you a beautiful set of custom forgings, but the almost $900 they charge is an awful lot to spend on a 273. If you want to run hypereutectic pistons in your 273, you're out of luck because hypereutectic pistons aren't available for the Mopar 273.

The second challenge is developing power in a performance application. The 273 can definitely make good power - the problem is that because of its small displacement you have to spin it really fast to get there. Also, the small bore size restricts the valve sizes you can run, which in turn limits the flow of air into the engine, which in turn limits the amount of power the engine will make. Does this mean that building a 273 is a waste of time and money? Not hardly, you just need to be aware of what you're getting into if you decide to build one.

Not every car needs to be a street racer. When I was in high school, my sister had a 65 Mustang with a 200 inline six that could burn the tires at will. My 64 Valiant station wagon with its 225 Slant Six also performs OK for a driver and gets good mileage as well. The 273 Mopar is quite a bit bigger than either of the sixes I've driven and should offer excellent performance in the right car. It's also quite a bit smaller than the next in line Mopar V8, so it should be able to deliver excellent economy as well.

I just picked up my 273 from the shop that is installing my new 318 and handling the 5 speed conversion on my 66 Barracuda. I've been trying to decide what to do with it - strip it for parts (the 273 has a forged crank that will fit a 318), try to sell it, through it away... In the end I decided to keep it. My garage space is limited though and I can't afford the luxury or storage space of just keeping something for the sake of keeping it. So I'm going to rebuild it - if it can be rebuilt. The valley looks horrible. Lots of black gunk like maybe it never had an oil change. I'm not sure about the bores, either. I am, however, an optimist. I got it mounted on a stand today and will start evaluating it over the next week (my wife is out of town, so what better way to spend quality time in my Man Cave?).

Assuming it's rebuildable, the only challenge would be finding affordable pistons. Both Summit Racing and Performance Automotive Warehouse list Mopar 273 pistons. Summit's ever shifting "estimated ship date" is currently listed as November 13, and I haven't called P.A.W. yet to see if they have them in stock. If I can find pistons and the block will clean up with a 0.030" bore though, I'm going to do it. It will be a performance with economy build, with the emphasis on economy. That means I'll be reusing as many of the stock parts as possible, including the cylinder heads.

Using the stock heads throws another twist into the mix. These are early style LA heads, so current after market intake manifolds won't fit without modification. So... my choices are to see what I can do with the stock 2 barrel manifold or modify a modern 4 barrel manifold to fit the heads. Either choice is interesting to me. I have a Holley 350 cfm 2 bbl that I've been dying to try on something, so that option would be fun. OTOH, it would also be fun to see what kind of improvement (for both power and economy) could be gained by upgrading to a modern 4 bbl manifold and carburetor.