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Just for reference, here is the fender tag for the car. Not sure if anyone cares.
man, that is a bare bones tag~ see the 31, thats a 273/4 and the 55 is an auto with heater. if you got the original 273/4, take the cam and intake and heads and put them on a 318. I did when I spun a 273/4 rod bearing and never looked back. It was faster as a lower-comp 318 than it was as a hi-comp 273 with the 4bbl intake and camshaft. Youll need a convertor ring for a later crank on an early trans as the crank convertor snout sockets were bigger in 68 crankshafts, just a 1/8 thick centering adapter ring.
You want to compare the 318 2 barrel with the 273 4 barrel in your byline. They are not comparable. Not sure what you had, but a 318 2 barrel is not even in the same league as any 273 4 barrel I had, stock to Wild. I could have as many 318's as I wanted and I have hopped them up for others. I kept all the 273's I could lay my hands on, no 318's. If you put all the good stuff in a 318 you are good to go. At that point I personally was on to 340's and HP 383's.
Yes, I put all the good 273/4 stuff on that 318 block and it rocked. Im going by blueprint posted Mopar numbers here and as an owner of a 273/4 survivor that got a 318 heart. I too later moved on up to a .060 over 340, then a std bore 340 I aquired, then took the plunge and went big: 451 stroker. I have since gained my wits back in this narrow chassis and have gathered another 273, a snailed 225 and an injected 403. from a past post on 273/4 dyno numbers. "...273/235 HP was re-factored by the NHRA down to 220 HP in 1976, then got another adjustment down to 210 HP..."
It will cost the same to build a 340 as 273 and not limited by early heads/intake bolt. Schumaker makes a kit with motor mts/ insulators/bolts to make the change- I have a set NIB I can sell for $100- check there website for now price-
OK, finally was able to take possession of the car and actually got to talk to someone who knew about it when it was purchased. Car was going to be a Drag car build and didn't come with an engine. The seller threw in a 273/2 with the deal, but I don't think they made a 273/2 Commando? Now knowing that the engine isn't the 273/4 Commando that I thought it was, I am thinking I am better off going with a 318, versus trying to get the 273/2 built up. Thoughts?
Take any bare block, 273, 318, 360, 340 and build it into what ever YOU want. For sure, a combo that rocks in a 340 will not work in a 273, just different animals. But point is, when you build a motor, you blueprint it into what you want. If done correctly any block can be made to reach its full potential. But what works for the street is different than what work on the strip right. Sort of reminds me of people running down the F body, you know the Volare/Aspen '76-80 cars. Their best came with a 360 4 bbl "smogger". Now it was the faster production engine of that era, even faster than the Vette. Say someone someone wants more power than stock for back in that day. He simple builds a better engine. It is a 360 block, he can change the stroke, he can change the cam, he can change the compression, he can recurve the dist., might even could use a bigger carb...... If we need fresh engine an not a woreout one, we can be the man that decide what it will be!
Commando 273 engines were 4 barrel engines and had a number of special HP parts. I'd first find out what you have. Casting numbers from the heads and block. Is your 273 solid lifter? Do you have exhaust manifolds and motor mount brackets? A friend of mine has a 67 4 speed Formula S Fastback and had his 273 dyno'd. With all the Commando good stuff and 2 barrel pistons, a small Isky E-4 cam, and a 600 Edelbrock carb the little 273 made 260+ hp at 5,500. In general If you are building any wedge engine, you should be able to get 1 hp per cubic inch and torque as well. A good 273 will move a 65 Cuda very well and get 20+ mpg. You are also limited by wheel well width. A High Performance 273 likes rpm and will easily run to 6,000 to 7,000 rpm with stock heads. I had a 64, 4 speed Cuda as a daily driver for decades. Loved that car. Any small block will really move that car. Here are some stock hp numbers from one of the Chrysler Racing manual. Notice that a 318 2 barrel does not make any where near 230 hp. Depending on what you have, all engines are similar in cost to build. What do you have available? What do you really want the car to do? Start there.
Well after the heated discussion that I created with this thread, I have some bad news. The friend helping us with the motor said that it probably isn't worth rebuilding. Not the news I wanted to hear, but we did find someone who might have a running 318 from an early 70's truck. I have yet to see said motor, but I think this will be a better long term and more pocket book friendly option versus trying to tear apart the 273/2 to rebuild. Thanks again for all the input on my questions!