Are all 273 V8's the same?

[Oldmanmopar]

found this on the web


Chrysler 273 LA Small Block
The Mopar 273 was Chrysler's first LA small block V8. It was introduced in 1964 with a 2-barrel carburetor and made 180 HP. In 1965, a high performance version called the Commando was introduced. The 273 Commando had a hotter cam, 4 barrel carb, and made 235 HP. In 1966, a limited edition racing version of the 273 called the Super Commando was offered. The Super Commando was equipped with steel tube headers, a 700 cfm Holley 4-barrel carburetor, a high lift mechanical camshaft, and made 275 HP. Production of the 273 spanned 6 years, lasting through the 1969 model year. The low end version was replaced by the Mopar 318, while high output versions were replaced by the Mopar 340.

 

[66fs]

I could see one or two. But all of the commando cars here have flat tops. Even this never touched car from the original owner. Could it be a 66 thing or a 4 speed thing. All of the cars here are 67 autos.

One original engine was removed and stored by the owner after installing a 340. it came with the yellow car. I have all the pistons Not one domed. I lost count of how many 273 commandos Todd and I have here. It would be mind blowing for someone to remove all the domed pistons from the engines here. These are commando cars and one Formula S coupe. All of them are E code

1st are those original pistons, or aftermarket? They look aftermarket. Oversize? For a long time 10.5:1 pistons were only available as custom. I've bought and parted a 67 Formula S in the 70's with 50,000 miles on it. It had domed pistons, I still have it. My 66 Formula S had domed pistons. I bought a virgin 273 Commando motor and trans from a member in the 80's it had domed pistons. Check an old Motors Manual or tune up guide from back in the day, they will list the Commando/Charger 273's compression ratio as 10.5:1. The 2 barrel motors will be listed as just under 9:1. The D Dart was so rare, most people do not know about it. Probably only 50 or so, but I do not know the number.

 

[CPDave]

I've had 3 273 Commando's apart, a '65, '66 (out of my Formula S), and a '67, all three had the same bank specific, above the deck, pop-up pistons. I suspect when we see the flat tops appearing, in 273 cars, and keeping in mind how these cars may have been operated by their original owners, we may be seeing dealer warranty replacement short blocks that the dealer (or Chrysler) saved a buck on (or someone swapped the Commando/Charger short or long block out from under the intake and distributor). Since MOPAR didn't start matching numbers until years later, we only have date codes to know if a block or head is "correct" for the car. And of course it is also Possible (but I view it as less likely) that MOPAR ran short of the pop-up castings in production and used the flat tops to fill in the gap.

It would be interesting to know what the spec's on the cams are in the various flat-top blocks...

 

[toolmanmike]

found this on the web


Chrysler 273 LA Small Block
The Mopar 273 was Chrysler's first LA small block V8. It was introduced in 1964 with a 2-barrel carburetor and made 180 HP. In 1965, a high performance version called the Commando was introduced. The 273 Commando had a hotter cam, 4 barrel carb, and made 235 HP. In 1966, a limited edition racing version of the 273 called the Super Commando was offered. The Super Commando was equipped with steel tube headers, a 700 cfm Holley 4-barrel carburetor, a high lift mechanical camshaft, and made 275 HP. Production of the 273 spanned 6 years, lasting through the 1969 model year. The low end version was replaced by the Mopar 318, while high output versions were replaced by the Mopar 340.

That guy is a dweeb. He has been corrected many times.

 

[toolmanmike]

How did Ma Mopar get high compression out of a 273 if the pistons, rods,crank and heads were all the same. They didn't. They used domed pistons to raise compression.

 

[toolmanmike]

From Motor Trend 273 Power Pac rebuild: Testing the Mopar 273 Power Pak on the Dyno

 

[toolmanmike]

My 66 273-4 barrel

 

[toolmanmike]

I've had 3 273 Commando's apart, a '65, '66 (out of my Formula S), and a '67, all three had the same bank specific, above the deck, pop-up pistons. I suspect when we see the flat tops appearing, in 273 cars, and keeping in mind how these cars may have been operated by their original owners, we may be seeing dealer warranty replacement short blocks that the dealer (or Chrysler) saved a buck on (or someone swapped the Commando/Charger short or long block out from under the intake and distributor). Since MOPAR didn't start matching numbers until years later, we only have date codes to know if a block or head is "correct" for the car. And of course it is also Possible (but I view it as less likely) that MOPAR ran short of the pop-up castings in production and used the flat tops to fill in the gap.

It would be interesting to know what the spec's on the cams are in the various flat-top blocks...

The 4 barre cam was bigger. There were some minor changes to the 4 barrel cam between the years. (not by much) 273 mild build cam

 

[CPDave]

The 4 barre cam was bigger. (not by much) 273 mild build cam

Yep, My point was, I was wondering which cam was in those flat-top blocks:

Std. 273 2 Brl (8.8:1):
Valve Lift: 0.395" 0.395"
Duration: 240ø 240ø
Opens: 14ø BTDC 58ø BBDC
Closes: 46ø ABDC 2ø ATDC

273 Commando (10.5:1):
Valve Lift: 0.425" 0.425"
Duration: 248ø 248ø
Opens: 14ø BTDC 56ø BBDC
Closes: 54ø ABDC 12ø ATDC

Without at least checking lift it's tough to know what was actually in those cars.

 

[toolmanmike]

Yep, My point was, I was wondering which cam was in those flat-top blocks:

Std. 273 2 Brl (8.8:1):
Valve Lift: 0.395" 0.395"
Duration: 240ø 240ø
Opens: 14ø BTDC 58ø BBDC
Closes: 46ø ABDC 2ø ATDC

273 Commando (10.5:1):
Valve Lift: 0.425" 0.425"
Duration: 248ø 248ø
Opens: 14ø BTDC 56ø BBDC
Closes: 54ø ABDC 12ø ATDC

Without at least checking lift it's tough to know what was actually in those cars.

Exactly. The 2 barrel .395 cam should have been in the flat top engines.

 

[Oldmanmopar]

All of the engines here are 67 automatic cars. The blue primered car I know for a fact is the original engine never touched or out of the car. Bought the car from the original owner been in a truck body in Tennessee for over 35 years.

The pistons are the original pistons from the engine pictured from the yellow car. That car was purchased from member gtsjohn with that original engine came with the car. What I find it hard to believe is that every car we purchased with a 273 had the pistons changed. We even had a 4sp dart GT. Off the road since 71. How could I end up with all the cars with replacement pistons or engines.

There must be another reason for these engines all having flat tops. You would think either Todd or I would at least have one engine with domed pistons out of at least 10 cars and engines. I just don't get it.

I found another early 4 spd 66 Barracuda S for parts for the Valiant we'll see what it has.

 

[66340SEDAN]

Pistons.....1965-1967 273 Commando engines had high dome pistons from the factory....10.5:1 compression engines....2bbl engines had flat pistons and they are different....here is a 273 HP piston

 

[66340SEDAN]

https://www.google.com/amp/s/www.hemmings.com/stories/article/1965-1967-chrysler-273-four-barrel/amp

 

[str12-340]

and none of this stuff about the pistons answers the OP's question about using the engine... yeeesh

 

[Dartvader440gt]

Ok, so as long as the engine is a 1967 or older, there should be no problems with it bolting up to a 65 B-body auto tranny? Going back to my original question .

 

[toolmanmike]

Ok, so as long as the engine is a 1967 or older, there should be no problems with it bolting up to a 65 B-body auto tranny? Going back to my original question .

It should but double check the crank register for the convertor snout. Sorry it got sidetracked.

 

[66fs]

and none of this stuff about the pistons answers the OP's question about using the engine... yeeesh

Answered affirmative in posts # 16 and 17.

 

[Dartvader440gt]

Thank you everyone. I am going to check the date on the block within the next day or two.

 

[Dartvader440gt]

Ok, update. Got a look at the numbers and pulled the valve cover off. Rockers are non adjustable. 318-2 on the side of the block. It's a 318. So false alarm. I do appreciate all the info. Now I know what to look for if the subject arises again in the future.

 

[dart4forte]

Were talking 273 motors....all other parts be damned. Early heads had the weird 5/16 intake bolts with their angles. Thats all. IIRC 69 273 was supposed to have hydro lifters but they seem to be pretty rare. The cams changed a little as well as compression ratio but the blocks were all the same.

68 was the first year for the hydro cam.

 

[MOPAROFFICIAL]

Ok, so as long as the engine is a 1967 or older, there should be no problems with it bolting up to a 65 B-body auto tranny? Going back to my original question .

64-67 small register vs 68 & up large register.
Obviously large crank register will fit both and you can buy a bushing for the early convertor nose to larger register...or have early guts put into a later convertor case .

 

[toolmanmike]

64-67 small register vs 68 & up large register.
Obviously large crank register will fit both and you can buy a bushing for the early convertor nose to larger register...or have early guts put into a later convertor case .

Never done that swap. Thanks for that info, it's good to know. I think I'll bookmark your post in case I need to find that info later.

 

[seabee]

66-69 had the normal intake bolt size and angle. All had forged crank and just the 64-67 had the mechanical valve train. 68 and 69 went to hydraulic and not adjustable.

I though there was a number of 66' 273s that had the earlier bolt angle-ed heads from 65' on them. I could be wrong (and often am) but I thought I got that information here at some point..

 

[toolmanmike]

I though there was a number of 66' 273s that had the earlier bolt angle-ed heads from 65' on them. I could be wrong (and often am) but I thought I got that information here at some point..

Nope. Not that I have ever heard. But who knows. Best not to go there. LOL

 

[pishta]

Ok, so as long as the engine is a 1967 or older, there should be no problems with it bolting up to a 65 B-body auto tranny? Going back to my original question .

Nope. bolt it in.