Difference in 273

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Chrome unsilenced air cleaner with "273" callout, Carter AFB carburetor, 4 barrel intake manifold, a slightly hotter camshaft, 10:5 to 1 domed pistons, a low-restriction single exhaust system/muffler, dual-point distributor, aluminum-finned/krinkle-black painted hemi-style valve covers. Did I forget anything besides the advertised 55 horsepower increase (235 HP vs. 180 HP)?
P.S. Yes, forgot about the chrome PVC cover and breather along with the upgraded valve covers.
 
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Pistons, cam, valve springs, 4 barrel intake, AFB carb, dual point ball bearing vacuume advance, 2.5 straight thru single exhaust, chrome unsilenced air cleaner, finned valve covers, chrome oil filler and pcv cover. Then you had the suspension and brake upgrades to go with it.
 
Different pistons, camshaft, dual point instead of single point distributor, larger better flow single exhaust system and of course 4bbl manifold with small carter 4bbl carb instead of 2bbl setup.
 
Never too old to learn. I didn't realize until a couple days ago that the Hp engines had stiffer valve springs.
 
dibbons said:
I always wondered about the valve springs, is there a source we can find to clarify the differences in those?
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Not sure about the 235hp engines...but here's specs on the 275hp used in the D/Darts. Those WERE stiffer, per page #3 of the factory tech bulletin....
0618171438b.jpg
 
I'm not sure about the valve springs. I haven't seen any documentation on that. And I believe the chrome PCV cap was only up thru 66.

Note that the Commando 273 engine package was completely independent of any performance suspension or brake packages. When you ordered the Commando engine as a line item, that's all you got. The HD suspension (heavier leaves and t-bars, with front sway bar) came with the Formula S option on Barracudas, or could be ordered as a separate item. Now, you HAD to take either the Commando 273 or the Super Commando 383 (67 up) when you ordered the Formula S package, but it didn't work the other way around (for the 273 -- Formula S was mandatory with the 383 in 1967). There were no accessories or dress-up items associated with the motor other than the Commando badge on the fender. My 67 FB was ordered with the Commando 273 as an extra cost option, plus HD suspension as a separate line item, minus sway bar (for credit), plus manual disc brakes (separate line item). It was a bench seat, column shift auto car.
 
Well, yeah, you had to have stiffer valve springs on the D/Dart... good grief, that thing had a radical race-only cam. I don't think that proves anything about the 235hp 273.
 
ronw said:
What is the difference between a 273 2BBL and a 273 4BBL Hipo?
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But...which "Hipo" wasn't specified. ;-) So I went all out! Lol!

Seriously though, I haven't seen any documention to suggest different springs in/on the standard 4-barrel vs. a 2-barrel engine.
 
The spring specs are in the blueprint section of the racing manual and if anyone has a 65, 66, 67 parts manual. I know they are different. They were close to 360 2 barrel springs. I always used 340 springs. They don't float at 330 pounds/inch. Documentation?? 67 Commando 273's and 383 had factory dress items. I've never seen an original Commando or Charger 273 without them.
 
The service manual lists different spring pressures for 2 bbl vs 4 bbl... (67 dodge)

273 Valve Springs.jpg
 
dibbons said:
I always wondered about the valve springs, is there a source we can find to clarify the differences in those?
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I got some specs from my service manual. I can post them tomorrow. Just a word of warning, they measured them different than they do today. Karl's specs look similar to my 66 manual specs.
 
Great info. on valve springs guys . Thank you very much.:thankyou: Love to learn even at my age.lol
Always thought 2bbl & 4bbl 273's used the same springs but checked my service manual also and low and behold there is info krazycuda posted. Since I have a set of 4bbl heads( on car ) and 2bbl heads ( laying in garage ) to compare that I'm pretty sure are both original. Checked this morning and the springs sure look slightly thicker to me on the commando heads than 2bbls.
 
Dartswinger70 said:
Makes me wonder what similar internals would do in a 318.
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If you are meaning going with decently high compression pistons than the stock 318 low compression pistons, then it would become a 273 on steroids.

It will be a lot more like a 340 than a 273 if the larger LA or Magnum heads and breathing parts are installed.

There are newer and a bigger variety of cams and such for these LA engines now, so it does not make so much sense to me to use the older cams.
 
No diffrence between 2bbl & 4bbl cylinder heads themselves. Other than springs & 1964-65 had smaller intake bolts and a bit diffrent angle. Otherwise heads were same between 2bbl & 4bbl.
 
In '68, the open chamber 675 heads came into being, and were on the 2 BBL 273's. But not sure what heads were on the 4 BBL's for that year.
 
67 is the last year that a 4 barrel intake or Carb was listed in my books. 68 was the first year for the hydraulic cam in the 273 and along with that came the 2 barrel carb. In 68 the 340 was born. It took the small block performance ball and ran with it!
 
nm9stheham said:
In '68, the open chamber 675 heads came into being, and were on the 2 BBL 273's. But not sure what heads were on the 4 BBL's for that year.
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I don't think that they made a 273 4 bbl in 68, that's when the 340 came out...

Who would want a 273 4 bbl when you can get a 340 4 bbl??? (No offense to the 273 guys....)

67 was the last year of the 273 4 bbl and solid cam in the 273... In 68 the 273 and 318 had the same hydraulic cam...
 
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