Information on the 273

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ethan santin

ethan santin

Buck eye jim you gotta go
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Hey there,

Ive gone and done some reaserch and have read some articles about the 273 already but I am very intrested in what anyone who has owned or owns a car with a 273 in it has to say about them. What makes them diffrent from other mopar small blocks? What kind of issues do they have? I would love to hear any general information about them if your willing to share. I personally dont own one, but ive seen and worked on a lot of mopars but haven never seen or worked on a 273 so I am just genrally curious about them.

Thanks for reading.
 
They Love to Rev... Smaller Bores mean less rotating weight. The Early Ones from '64-'66 had Factory Forged CrankShafts in them (Like Mine)
One was a Stndrd 2 barrel 180hp and the other a Commando 4 barrel had a Dual Point Distributor, Larger Cam and Special 10.5 to 1 Compression Pistons that made 230hp!
Mine is Standard with some mods and Runs Like Hell! They're expensive to build because of the Lack of Interest and Parts...
@66fs is the Guy to ask... He would compare a built one to a Big Block if you asked him too!

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I have had two different 273 2 bbl stock engines in 1967 b-bodies. They were running good, hitting on all 8 cylinders and not burning oil. So in decent used condition. Seemed to be underpowered and unimpressive Compared to the same year stock 318, which was a much better daily driver, more power, better fuel mileage. All with 2.94 gears and stock size 205/75/14 tires.
 
The idea they like to rev is cause of air flow they have a similar head flow to cid ratio as a 340, obviously less hp potential then a 340 cause of overall head flow and rpm needed.

Basically the difference between a 2bbl 318 and 273 is bore size 3.91 vs 3.625 and rest is fairly identical for all practical purpose why people general group them together 273/318 and 360/340 cause each group has there own heads and engine mount. Sometimes there group by crank stroke so 273/318/340 with 3.31 and 360 with it's 3.58 and larger main bearing. I group by bore size 273/3.625 small and 318/360/340 3.91/4/4.04 same ballpark. A 4 inch bore is just over halfway (3.98) between 273 and 400 bore of 3.625 vs 4.34.

Other than bore size, early years having a different intake bolt angle, closed chamber heads and solid cam, other then that and being mopar 1st LA engine and 1st high performance LA with 235hp there's not too much more to say about them.
 
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Other than CID displacement they are identical to most mopar small blocks. Flat out reliable.
Not much torque to them.
 
Steel crank really allowed them to wind up to higher rpm’s smoothly and the reliability made them such a good little engine.
They look great in any engine bay but I am biased, I like red.
318s little brother!
My bud has one in his 67 dart and it runs like a top and is all original!
A little hard for him to do a one wheel peel as his is stock 2 bl.
Like any engine if you throw $ at it they can perform with gears and such, especially in a small car.
Like the 318 they didnt get the recognition they deserved because of the 340’s.
If Chrysler had put more 273 commandos and d dart 273’s in more cars people would be ranting about them but since most of them were 2 bls they got a bad reputation similar to the smog 360’s.
I like them, they look nice and can be made to perform with some work.
 
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QUINN FORBES said:
Like any engine if you throw $ at it they can perform with gears and such, especially in a small car.
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I had to quote this.It says it all.
Stone stock the disadvantage of the 273 is torque.45 cubic inches makes a big difference between it and a 318.
My 68 Valiant came stock with a 273 2bbl.They are a quality engine.

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The reason I like 273's are they have small port, closed chamber heads, that will flow almost as much as 360 heads. From 64 to 67 they had solid lifter valve train and cams, forged steel cranks, and bushed forged steel rods. Pistons are almost to the deck and nut sunk like the larger motors. In 64 and 65 they had a odd angled intake bolts. The 235 hp versions from 65 to 67 (Commando for Plymouth and Charger for Dodge) had a larger cam (but still very small) 10.5:1 pistons, a nice Carter AFB with a secondary velocity valve and intake manifold, Prestolite quicker curve dual point ball bearing vacuum advance distributor, 2 1/2 inch single exhaust with 2 straight thru mufflers in series, chrome air cleaner breather, and PCV cup, and black krinkle valve covers with finned aluminum wire looms. I always liked a high revving engine so I preferred the smallest engine with the best heads. Easy 6,000 to 7,000 rpm with a 260-268 duration cam. I always ran a 4 speed with the 273 so horse power always trumped torque. Lower gears will multiply torque if that is where you want to go. A High Performance 273 is a perfect engine for an early A with a 4 speed. 68 and 69 273s were a downgrade with the cast crank, hydraulic cam and valve train, and the open chamber 318 heads. However the good thing about the later 273 was the piston. The 68 and 69 273 pistons were .030 higher in the bore (to compensate for the open chamber heads) making them near zero deck. Then just add the earlier closed chamber heads and you get close to optimum quench and compression ratio for pump gas.

Compared to other Mopar small blocks, they are all very good and can easily be made into performance engines. Except for the 340 and HP 360s they had very small cams, and that, valve springs, and a 4 barrel carb is where to start. 340 was king, a 318 can run with a 340 if you use all the good stuff, 360s were used in pick ups and large cars, but like 318s can also easily run hard using the 340 stuff and they already have good heads.
 
In 64 they were the first LA V8. (Light A) They replaced the physically larger Poly 318 for use in the smaller bodied Darts, Valiants, and the new Barracuda model.

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QUINN FORBES said:
Smart move replacing the poly with the 273.
lMO.
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The Poly was a great engine but it was physically too big for the smaller cars coming out in 63. In fact, the 63's couldn't even fit a V8 in due to the firewall design. If they didn't design a new head they wouldn't be able to put a V8 in the mew models. There is a lot of similarities between the Poly and the LA engines. Heads and valve timing are the biggest differences.
 
toolmanmike said:
The Poly was a great engine but it was physically too big for the smaller cars coming out in 63. In fact, the 63's couldn't even fit a V8 in due to the firewall design. If they didn't design a new head they wouldn't be able to put a V8 in the mew models. There is a lot of similarities between the Poly and the LA engines. Heads and valve timing are the biggest differences.
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QUINN FORBES said:
Smart move replacing the poly with the 273.
lMO.
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You can actually make a case for the Poly being a better head than the LA. I don't want to derail the OP's thread too far, but in a nutshell; the Polys were individual runner, straighter ports, better valvetrain geometry, and a polyspheric (some call them the "semi-hemi") combustion chamber. The width killed it for A body use (as previously stated), and higher manufacturing costs caused its ultimate demise. The LA heads were really just a compromise design to get a wedge head on an existing block architecture, and inherited all kinds of weird geometry issues and port compromises in order to make them work- but they've been the standard for sixty years now. Who knows where we'd be performance-wise if the poly heads had been getting some lovin' for all these decades instead of the LA heads... just food for thought.
 
Agree, Had a 66sport fury with the “wide block” poly in it…another regretful sale.
I’m not against the 318 poly its just the bolt ons were readily available for the 273.
 
though it's a race engine, matt steens 273 super stocker , runs 10.30 & 130 mph in a 66 valient. in stock eliminator the 180 hp is a great combo. just food for thought.
 
Bear in mind that when they were made there were lots of small engines. The SB chev was not that old and it started as a 265. Ford a 221, then 260, then 289. And lots and LOTS of 6 cyl powered cars.

AN ANNOYING STORY FROM THE OLD DAYS. Towards the end of the 70RR I owned, I decided to yank the 340 out of it (that I'd swapped in) and freshen it up, stick it in my old Landcruiser. I needed "something" in the mean time. Bought a "318" from a friend in a 65 B body, and it turned out to be a 273!!! In it went, with the Hedmans in the RR. It actually did OK, the RR had an 833, and Dana 60 / 3.54 gear

This then friend had a 50 GMC with a "built" 250 bored Chev 6, Clifford, Holley, headers, and an adapted Chrysler A833. He thought it was pretty hot.

One Saturday we all were going some damn place and got into a little impromptu thing on the highway, and it turned out the FIFTY DOLLAR 273 could kick that GMC's ***!!!! Bone stock 2BBL except for the headers and duals LOLOL
 
The 273 2bbl is a fine, reliable engine, but will seem underpowered compared to other V8s. The 4bbl is a completely different animal. It still suffers from lack of torque compared to larger displacement engines, but it revs like crazy. To get the most out of it you want a lightweight car with a manual transmission — then it can be a lot of fun. Mine is in a 3300lb car with a stock 904 and a 3.23 axle, so it doesn't have neck-snapping performance, but it really pulls from say, 40 to 80mph. The torque & HP graphs from the factory brochures are very informative: the 2bbl has a torque peak at 1600rpm, and the 4bbl has a torque peak at 4000rpm — that's a very different proposition.

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Just found out 273-TALK is NOT about small displacement Mopar V8 engines.

It's the suicide prevention hotline.

Coincidence?
 
mvh said:
The torque & HP graphs from the factory brochures are very informative: the 2bbl has a torque peak at 1600rpm, and the 4bbl has a torque peak at 4000rpm — that's a very different proposition.
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If I'm seeing it right even though the 4bbl peaks at 4000 rpm it's pretty flat all the way down low making similar torque. 273 meant to be a competitor to the /6 not 340/360 but being it uses pretty much the same parts it still has lots potential if one chooses. 250-350 hp shouldn't be hard to do above that rpm gets to high for most.
mvh said:
View attachment 1716079504.
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Here's a dyno of 473 hp @ 7900 rpm 334 tq at 7100 rpm 273/292

273 said:
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Here's some service information from Ma Mopar for the 66's and the D Dart package. How to hot rod your 273. 1966 style.

275 HP 273 Tune-Up Tips March 1966 001.jpg


275 HP 273 Tune-Up Tips March 1966 002.jpg


275 HP 273 Tune-Up Tips March 1966 003.jpg


275 HP 273 Tune-Up Tips March 1966 004.jpg


275 HP 273 Tune-Up Tips March 1966 005.jpg
 
perfacar said:
though it's a race engine, matt steens 273 super stocker , runs 10.30 & 130 mph in a 66 valient. in stock eliminator the 180 hp is a great combo. just food for thought.
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What heads is he running to turn 10.30s?
 
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