Building a 273

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273Dynamite

273Dynamite

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Hi,
im building a 1969 273 with a 904 automatic trans for my 2 door 1949 Plymouth.
its a stock 2 barrel carb i believe 180-190 horsepower. Me and my uncle want to build it to the super commando specs ranking in at 275 horsepower but trying to push it up to 300 horsepower. I acquired a '65 Commando intake #2465726
1949 Plymouth.jpg
1949 Plymouth.jpg
, Im not sure if that will fit on a '69 block. I know i could use the Edelbrock LD4B intake but would like to see if i can use the '65 commando intake. Also have a '64 8 3/4 rear end for the Plymouth, should bolt right in, its an inch bigger than original rear end. Just wanted to see anyone else's input on this build and get any other opinions and options for it. thanks!

1969 273.jpg


273 commando Intake.jpg
 
65 commando intake will need mount holes oblonged slightly as 65 had different printed mount holes vs 69 heads.(no big deal). If you arent shy on spending $$ for commando pistons from Egge, your goal is easily attainable!
Good luck:thumbsup:
 
The intake might be a problem.

In 66 they changed the angle and size of the intake manifold bolts

So a 65 and older while the same dimensionally will have issues bolting onto the 69 heads.

I understand the intake can be machined to work but for the money you might want to either get 65 and older heads or a 66 and newer intake.

Also I applaud you for going 273, but a 318 would be much cheaper, the pistons on a 273 are in the grand range alone.
 
Welcome. You are right, the 1964 and 5 273 manifolds don't bolt up to 66 and newer heads. The bolt size is different as well as the angle. The holes can be modified and angular washers used to make it work. There are numerous threads here on the site about that. I must correct you about something, The never was a "Super Commando" 273. Dodge called their 4 barrel engines "Charger" and Plymouth called theirs Commando. Both were 10.5/1 compression with 4 barrel intake and carb, a slightly larger solid lifter cam, dual point distributor, special valve covers, a chrome unsilenced air cleaner, and special large single exhaust with a square resonator tip. In 1966 Dodge came out with a D Dart that had a modified 273-4 barrel engine with 275 horse for NHRA's D stock class.
 
65-66 273 Commando engines have a different intake/cylinder head interface angle than the 67 and up years. They all had 10.5:1 pop up pistons (above deck). You should be able to get them from Egge. 65'
 
4spdragtop said:
65 commando intake will need mount holes oblonged slightly as 65 had different printed mount holes vs 69 heads.(no big deal). If you arent shy on spending $$ for commando pistons from Egge, your goal is easily attainable!
Good luck:thumbsup:
Click to expand...


Thank you for your reply! Going to look into the commando pistons from Egge!
 
Dana67Dart said:
The intake might be a problem.

In 66 they changed the angle and size of the intake manifold bolts

So a 65 and older while the same dimensionally will have issues bolting onto the 69 heads.

I understand the intake can be machined to work but for the money you might want to either get 65 and older heads or a 66 and newer intake.

Also I applaud you for going 273, but a 318 would be much cheaper, the pistons on a 273 are in the grand range alone.
Click to expand...


Thank you for your reply! I thought about going with a 318 but the 273 was just calling my name for my '49! haha might have to get the intake machined to make it work
 
273Dynamite said:
Hi,
im building a 1969 273 with a 904 automatic trans for my 2 door 1949 Plymouth.
its a stock 2 barrel carb i believe 180-190 horsepower. Me and my uncle want to build it to the super commando specs ranking in at 275 horsepower but trying to push it up to 300 horsepower. I acquired a '65 Commando intake #2465726View attachment 1715959407 View attachment 1715959407 , Im not sure if that will fit on a '69 block. I know i could use the Edelbrock LD4B intake but would like to see if i can use the '65 commando intake. Also have a '64 8 3/4 rear end for the Plymouth, should bolt right in, its an inch bigger than original rear end. Just wanted to see anyone else's input on this build and get any other opinions and options for it. thanks!

View attachment 1715959408

View attachment 1715959409
Click to expand...
Another thing that was done from 64-67 with the 4 barrel engines is a solid lifter cam and adjustable rockers. 68 and 9 had hydraulic. You can find rockers, shafts, and pushrods for sale here quite often.
 
toolmanmike said:
Welcome. You are right, the 1964 and 5 273 manifolds don't bolt up to 66 and newer heads. The bolt size is different as well as the angle. The holes can be modified and angular washers used to make it work. There are numerous threads here on the site about that. I must correct you about something, The never was a "Super Commando" 273. Dodge called their 4 barrel engines "Charger" and Plymouth called theirs Commando. Both were 10.5/1 compression with 4 barrel intake and carb, a slightly larger solid lifter cam, dual point distributor, special valve covers, a chrome unsilenced air cleaner, and special large single exhaust with a square resonator tip. In 1966 Dodge came out with a D Dart that had a modified 273-4 barrel engine with 275 horse for NHRA's D stock class.
Click to expand...
toolmanmike said:
Welcome. You are right, the 1964 and 5 273 manifolds don't bolt up to 66 and newer heads. The bolt size is different as well as the angle. The holes can be modified and angular washers used to make it work. There are numerous threads here on the site about that. I must correct you about something, The never was a "Super Commando" 273. Dodge called their 4 barrel engines "Charger" and Plymouth called theirs Commando. Both were 10.5/1 compression with 4 barrel intake and carb, a slightly larger solid lifter cam, dual point distributor, special valve covers, a chrome unsilenced air cleaner, and special large single exhaust with a square resonator tip. In 1966 Dodge came out with a D Dart that had a modified 273-4 barrel engine with 275 horse for NHRA's D stock class.
Click to expand...


Thank you for reply! would the heart chamber heads from '89-'91 dodge dakota 318 work on the '69 273?
 
4spdragtop said:
65 commando intake will need mount holes oblonged slightly as 65 had different printed mount holes vs 69 heads.(no big deal). If you arent shy on spending $$ for commando pistons from Egge, your goal is easily attainable!
Good luck:thumbsup:
Click to expand...



273Dynamite said:
Thank you for your reply! Going to look into the commando pistons from Egge!
Click to expand...

would you know if the heart chamber heads from '89-'91 dodge dakota 318 work for the '69 block?
 
273Dynamite said:
Thank you for reply! would the heart chamber heads from '89-'91 dodge dakota 318 work on the '69 273?
Click to expand...

I believe any head other than the original 273 closed chamber head will lower the compression ratio, which will thwart your HP goal. BTW, 300hp is probably not realistic —275hp would be a very extreme build for the street. More things to consider: You need to factor in the weight of that '49 compared to a narrow-body A. I would imagine as a body-on-frame it is considerably heavier. A high HP 273 build will have a very high RPM torque peak (factory Commando was 4000rpm!) — it will not have the kind of low-end grunt that moves a heavy car off the line. I have a factory Commando 273 in a 67 fastback (about 3400lbs) with a 904 and a 3.23 SG — it will not spin the 215/70 tires. You will need a super high stall convertor and a 4.11 rear to get any kind of launch.
 
273Dynamite said:
Thank you for reply! would the heart chamber heads from '89-'91 dodge dakota 318 work on the '69 273?
Click to expand...
The #302 casting heads would work fine. They are very close to the 273 heads and have induction hardened valve seats which is a plus.
 
Rather than modify the 65 4 barrel intake you have to fit your (or later) heads, why not sell it to someone who could use it on their 64/65 273. There are so many reasonably priced aftermarket that could help you achieve you horsepower goal.
 
65 Dartman said:
Rather than modify the 65 4 barrel intake you have to fit your (or later) heads, why not sell it to someone who could use it on their 64/65 273. There are so many reasonably priced aftermarket that could help you achieve you horsepower goal.
Click to expand...
Smart idea.
 
65 Dartman said:
Rather than modify the 65 4 barrel intake you have to fit your (or later) heads, why not sell it to someone who could use it on their 64/65 273. There are so many reasonably priced aftermarket that could help you achieve you horsepower goal.
Click to expand...


i can do that as well, i might just have to put that intake up for sale
 
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